Re: [Drakelist] R-4C IC Product Detector

[Paul Christensen]

Byron,

The datasheet calls for +12V, but it also shows examples of lower +Vcc.  It's 
in the same class as the NE602/612 DBMs that function at +9V.  As a solid-state 
balanced mixer used as a product detector, I can't image a performance hit by 
running the supply down to +10V.

When using the LM383/LM380, and TDA-series audio amp devices, my experience has 
been that hum/buzz rejection is greatly improved with wiring care, but residual 
hiss may be objectionable when using modern headphones.  I couldn't live with 
it, so I looked for other solutions.   Some options:

1) Through a coupling cap, bring the AF Control wiper arm out to a spare rear 
panel RCA jack (or pig-tail jack).  Then use a high quality external amp like a 
used Marantz;
2) Construct a simple push-pull audio amp using low-noise transistors.  For 
ultra-simplicity, I like the KK7B design that uses headroom boosting emitter 
caps.  See http://www.qrp.pops.net/af-amp-2008.asp ;
3) Construct a low-noise, precision Class-AB amp using one of several designs.  
Generally, these designs use 2-3 biasing diode to allow a small amount of 
collector-emitter current to flow in the absence of an input signal.  These 
designs have very low noise and distortion characteristics, owing to the use of 
the diodes and low noise figure transistors in the high-gain stages;
4) If you end up using the LM383 amp anyway, then consider using an in-line 
headphone attenuator and dial-in the amount of attenuation that reduces hiss to 
an acceptable level.  Of course, as a trade-off, the LM383 is working harder 
and the source Z increases.  Radio Shack and on-line sources sell these.

I'm using the SM0VPO amp design.  The circuit board is available from FAR 
Circuits and component values as well as the schematic are available on the 
SM0VPO website.

If you primarily use stereo headphones, consider replacing the mono headphone 
jack with an enclosed Switchcraft or Neutrik Tip-Ring-Sleeve (TRS) stereo type. 
  I would avoid open-frame jacks.  Feed the Drake output audio to both L and R 
channels.  Now, you'll never need a mono-to-stereo adapter.  If you have an old 
set of phones with a Tip-Sleeve plug, that will require replacement with a TRS 
type plug -- or use an adapter in those rare instances.

Paul, W9AC
   



  - Original Message - 
  From: Byron Tatum 
  To: drakelist@zerobeat.net 
  Sent: Sunday, March 31, 2013 9:53 PM
  Subject: [Drakelist] R-4C IC Product Detector


  Hello-
  I am in the process of installing some upgrades in my R-4C, an early one 
(18K SN range) that has the 6HS6's. The INRAD 8 KC 5645 KC first IF filter was 
in when I bought it, so at least I have a little bit of protection for that 
second mixer.
  I upgraded the power supply with the 7812 regulator and better 
electrolytic caps all around, per WB4HFN info combined with Sherwood info.
  Today I built the IC product detector using a TL442CN, installed it and 
appears all is well. I thought I would post this as I believe the TL442CN is an 
obsolete device. The TI SN76514 is an identical chip, it was used in the Mihuzo 
9 Mhz SSB boards as the balanced modulator. One thing, I am powering mine fom 
the +10 VDC that is provided for BFO, as that terminal was very near the 
module. Is itnecessary to have the full 12 VDC on the chip?
  I wish to do the sudio amp upgrade, mostly to get rid of the heat, but 
also to have a little better audio. I am thinking of going with the LM383T as 
done by Sherwood, but saw a video of an R-4C sporting a "D-Labs" audio upgrade. 
I cannot find any additional info on this. Thought I would ask for advice 
before I proceeded with the audio changes.
  Thanks, Byron WA5THJ  


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] VTVM Probe with DMM

[Paul Christensen]

Good solution, Paul!  Mentally dividing by ten is easy enough and you
retain all of the advantages of using the VTVM probe.

Dennis AE6C


Well'sorta.  The divide by ten works well and it's an easy mental 
exercise.  But in creating a 1 meg/100K divider, the load across the voltage 
sampling point is reduced from 10 meg to 1 meg.  That undermines the purpose 
of the resistive probe except that the effects from cable capacitance and 
lead inductance are swamped.  But if the source Z providing grid voltage, 
for example, is greater than 100K big errors will start setting in.


So...next I'm going to change the 1 meg resistor in VTVM probe to 10 meg 
(like the 100x probe), and then try a variable shunt at the DMM end to find 
the value where 10:1 is achieved.  That 10 meg is a high value for low 
voltage readings and I'm not sure how stable readings will be.  I think 10 
meg is commonly available in carbon film, but tougher to find in metal film.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] VTVM Probe with DMM

[Paul Christensen]

Dennis' suggestion of using a 100x probe got me to thinking of an 
alternative as the 100x scope probes are sorta' pricey, even on the used 
market.  As Dennis points out, the 100x scope probes are useful when 
sampling high voltage, typically greater than 1KV.  Since my focus has been 
with the grids of tube receivers, these measurements (even into the hundreds 
of volts) are adequate with the right 10x probe.


The 100x probe uses a 10 meg sampling resistor with a 100K shunt at the 
scope input.  Most scopes have a ~ 1 meg input Z.  The input Z of my Fluke 
8060A computes to 10.5 meg and is a value that is probably close to most 
portable DMMs.


Taking Dennis' suggestion, I used a 1 meg Simpson VTVM probe and shunted it 
with a value close to 100K to create the necessary 10:1 ratio.  A 200K pot 
was used to find a value that produced an exact 10:1 ratio.  For the Fluke 
8060A and my Simpson VTVM probe, that value is 112.5K.  I then created shunt 
consisting of two resistors in series whose total value is 112.5K and 
inserted this combination into a Pomona dual banana jack.  Different shunt 
jacks can be created if one wants best accuracy over a choice of DMMs in the 
shack.


In the links below, notice that the Simpson probe is connected to a 
BNC-to-dual banana adapter with standard 3/4" pin spacing.  The adapter has 
holes to allow shunting from a dual banana connector; the latter of which 
has the 112.5K resistor combination.  The black plug simply plugs into the 
red plug.


http://tinyurl.com/bc6ggo8

http://tinyurl.com/b56tfm5

Testing this idea in the real world shows that Dennis' idea works in a 10x 
configuration.  For example, when a +12V source is measured, the DMM reads 
1.2V.  It's then just a simple matter of multiplying displayed results by a 
factor of 10 which is a whole lot easier than using the DMM's RELative 
button and trying to find a 1.07V source as the calibrating reference.


It appears good accuracy can be achieved when using a DMM with a traditional 
VTVM probe.  The VTVM probe has the benefit of a 1 meg isolation resistor 
which is highly useful for grid readings.  The trade-off is the requirement 
of multiplying displayed readings by a factor of 10 -- the same as mentally 
moving the display's decimal place to the right by one digit.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] VTVM Probe with DMM

[Paul Christensen]

Dennis,

Many thanks.  I'll give that a try once I find a set of 100x probes. Darn, I 
didn't know 100x probes even existed for scopes as I've only worked with 10x 
types for the past 30 years!


Paul, W9AC

- Original Message - 
From: "Dennis Monticelli" 

To: "Paul Christensen" 
Cc: 
Sent: Wednesday, November 21, 2012 3:38 AM
Subject: Re: [Drakelist] VTVM Probe with DMM



Paul,

The best probe I have found for the purpose are the old 100X scope
probes.  They have a very low capacitance on the order of 2.5pF in
parallel with 10Meg so circuit loading is minimal.  Most have extra
voltage capability which is handy for working around transmitters.
While designed for AC & DC measurements via scopes, you can use them
accurately with DMM's because the 100X divider swamps out the loading
effect of the DMM.  The numerical accuracy of the DMM compensates for
the high voltage division ratio.

Dennis AE6C

On 11/17/12, Paul Christensen  wrote:
I finally got around to trying a good 'ole fashion VTVM probe with a 
Fluke
DMM.  Recall that most VTVM probes have a switch that allows for either 
DC

Volts in one position, then AC/Ohms/mA in the other position.  The DC
position typically has a 1-meg isolation resistor, highly useful for VT 
grid


measurements.   Without value compensation, a modern DMM cannot use such 
a

probe and is otherwise useless for serious tube receiver work.

I took a Simpson VTVM probe with a BNC connector and connected it to a
Pomona BNC-to-Banana adapter with standard 3/4" centers.  With the 
adapter,


the probe easily connects to a DMM.  My first measurement was a precise 
+12V


source.  When using the VTVM probe in the DC position (series 1-meg
resistor), the DMM displays +10.93V.  So, +1.07V is being dropped across 
the


1-meg resistor.  Assuming the resistor is close to 1-meg in value, the 
input


Z of my Fluke 8060A calculates to 10.215 meg.  Essentially, a 10:1 
voltage
divider is being created between the 1-meg iso-resistor, and the internal 
Z


of the DMM.  The drop is creating the value discrepancy.  VTVMs are
compensated in design and manufacture for this.

I have several Fluke DDMs, including 8060A (my favorite DMM), and an
advanced model 189.  However, peering through the manuals, I see no setup
routine to create a user-defined DC offset.  What I want is the ability 
to
measure a precise DC voltage, then enter a menu that allows me to assign 
a

new display value to compensate for the voltage drop across the
iso-resistor.  I have a lab-grade Keithley bench-type DMM that does allow
for such an offset, but hauling it around is a pain.

So, does anyone know of a DMM that allows for DC voltage offset?  This is
different than the "Relative" button seen on many DMMs.  Relative is used 
to


"zero the display" for any input value.  I want the same thing but 
instead

of zero, assign a new value of my choice.

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] VTVM Probe with DMM

[Paul Christensen]

Curt,

Yes, that works but it will not save to memory.  So, each time the DMM is 
powered up, I would need to set the Fluke 8060A against the 1.07V reference. 
And probably, the 189 may need a slightly different reference voltage for 
best accuracy.  It's an inconvenience, but it may be worth building a 
precision voltage regulator in a small project box, powered from a 9V 
battery.  I have not found a precision low-voltage regulator that will 
output below +1.24 V.   I could use a pass transistor after the regulator, 
fed from a pot as a voltage divider to get it adjustable down below +1.24V. 
To invert the sign to achieve -1.07V, the leads would be reversed just for 
calibration.


I've not had a good experience troubleshooting the grids of receiving tubes 
when using a DMM.  There's often enough distributed lead C that creates 
measurement problems.  I rarely run into this when using a VTVM and a 
switchable 1-meg probe.  Nothing wrong with using a VTVM or an FET VOM with 
an isolated probe, but like my Keithley DMM, they're not as portable as I'd 
like.


Paul, W9AC


- Original Message - 
From: "Curt Nixon" 

To: 
Sent: Saturday, November 17, 2012 2:22 PM
Subject: Re: [Drakelist] VTVM Probe with DMM


Hi Paul.  Wouldn't it be the same thing if you set-up a reference voltage 
that is -1.07V or whatever the drop is and then pushed the relative 
button?


If all you are trying to do is improve upon the input Z of the DMM, , my 
opinion is that I have never seen a measurement in troubleshooting any 
tube set that could not be done with a modern DMM.  At 10M inputZ, it 
isn't going to do much in the way of load.


Using one for an RF probe is slightly more of an issue but with a properly 
built RF probe, it still is no real issue.


Perhaps I have misunderstood what and why you are trying to acheive.

FWIW

Curt
KU8L

On 11/17/2012 12:29 PM, Paul Christensen wrote:
I finally got around to trying a good 'ole fashion VTVM probe with a 
Fluke DMM.  Recall that most VTVM probes have a switch that allows for 
either DC Volts in one position, then AC/Ohms/mA in the other position. 
The DC position typically has a 1-meg isolation resistor, highly useful 
for VT grid measurements.   Without value compensation, a modern DMM 
cannot use such a probe and is otherwise useless for serious tube 
receiver work.


I took a Simpson VTVM probe with a BNC connector and connected it to a 
Pomona BNC-to-Banana adapter with standard 3/4" centers.  With the 
adapter, the probe easily connects to a DMM.  My first measurement was a 
precise +12V source.  When using the VTVM probe in the DC position 
(series 1-meg resistor), the DMM displays +10.93V.  So, +1.07V is being 
dropped across the 1-meg resistor.  Assuming the resistor is close to 
1-meg in value, the input Z of my Fluke 8060A calculates to 10.215 meg. 
Essentially, a 10:1 voltage divider is being created between the 1-meg 
iso-resistor, and the internal Z of the DMM.  The drop is creating the 
value discrepancy.  VTVMs are compensated in design and manufacture for 
this.


I have several Fluke DDMs, including 8060A (my favorite DMM), and an 
advanced model 189.  However, peering through the manuals, I see no setup 
routine to create a user-defined DC offset.  What I want is the ability 
to measure a precise DC voltage, then enter a menu that allows me to 
assign a new display value to compensate for the voltage drop across the 
iso-resistor.  I have a lab-grade Keithley bench-type DMM that does allow 
for such an offset, but hauling it around is a pain.


So, does anyone know of a DMM that allows for DC voltage offset?  This is 
different than the "Relative" button seen on many DMMs.  Relative is used 
to "zero the display" for any input value.  I want the same thing but 
instead of zero, assign a new value of my choice.


Paul, W9AC

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] VTVM Probe with DMM

[Paul Christensen]

I finally got around to trying a good 'ole fashion VTVM probe with a Fluke 
DMM.  Recall that most VTVM probes have a switch that allows for either DC 
Volts in one position, then AC/Ohms/mA in the other position.  The DC 
position typically has a 1-meg isolation resistor, highly useful for VT grid 
measurements.   Without value compensation, a modern DMM cannot use such a 
probe and is otherwise useless for serious tube receiver work.


I took a Simpson VTVM probe with a BNC connector and connected it to a 
Pomona BNC-to-Banana adapter with standard 3/4" centers.  With the adapter, 
the probe easily connects to a DMM.  My first measurement was a precise +12V 
source.  When using the VTVM probe in the DC position (series 1-meg 
resistor), the DMM displays +10.93V.  So, +1.07V is being dropped across the 
1-meg resistor.  Assuming the resistor is close to 1-meg in value, the input 
Z of my Fluke 8060A calculates to 10.215 meg.  Essentially, a 10:1 voltage 
divider is being created between the 1-meg iso-resistor, and the internal Z 
of the DMM.  The drop is creating the value discrepancy.  VTVMs are 
compensated in design and manufacture for this.


I have several Fluke DDMs, including 8060A (my favorite DMM), and an 
advanced model 189.  However, peering through the manuals, I see no setup 
routine to create a user-defined DC offset.  What I want is the ability to 
measure a precise DC voltage, then enter a menu that allows me to assign a 
new display value to compensate for the voltage drop across the 
iso-resistor.  I have a lab-grade Keithley bench-type DMM that does allow 
for such an offset, but hauling it around is a pain.


So, does anyone know of a DMM that allows for DC voltage offset?  This is 
different than the "Relative" button seen on many DMMs.  Relative is used to 
"zero the display" for any input value.  I want the same thing but instead 
of zero, assign a new value of my choice.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4C Hum and audio transistor

[Paul Christensen]

I tried one, but to my ears, there's too much hiss with some high-end 
headphones with the AF control at low settings and even full CCW.  I've tried 
the LM383, LM380, and TDA2002.  The hiss can be reduced with an in-line 
attenuator, then running the AF control at a higher level to compensate.  I 
would rather just deal with the root issue and solve it.

Paul, W9AC
  - Original Message - 
  From: kc9...@aol.com 
  To: w...@arrl.net ; drakelist@zerobeat.net 
  Sent: Wednesday, October 31, 2012 2:39 PM
  Subject: Re: [Drakelist] R4C Hum and audio transistor


  Why not install a Sherwood audio kit ...I have one in mine..works FB
  73,
  Lee

  -Original Message-
  From: Paul Christensen 
  To: drakelist 
  Sent: Wed, Oct 31, 2012 2:37 pm
  Subject: Re: [Drakelist] R4C Hum and audio transistor


  Max,

  I'll get crucified for saying this, but that class A transistor stage was 
poorly designed -- and I think we can dispense with the "but they didn't have 
cost-effective transistor technology back thirty years ago" as an excuse.  A 
two-transistor complementary-symmetry PP pair running class AB and a moderate 
amount of negative feedback would have sounded substantially better, and 
produced much less heat.  

  As an example, look at the Marantz, Sansui, Kenwood, and other mid-fi 
Japanese audio amplifiers being produced during the same period.  Those 
designs, or a variant, could easily have been leveraged into the R-4C.  
Eliminate the audio output transformer and tap the symmetry pair mid-point, 
then couple with 500+ uF of series coupling C.  I don't know what Drake's cost 
was for the audio output transformer, but I have to believe the production cost 
difference between the transformer and an extra audio output transistor, and 
surrounding passive parts would have been reasonably minimal.

  I jettisoned the R-4C AF stage after the volume control and won't be going 
back.

  Paul, W9AC
- Original Message - 
From: Max Cotton 
To: drakelist@zerobeat.net 
Sent: Wednesday, October 31, 2012 2:10 PM
Subject: [Drakelist] R4C Hum and audio transistor


I have a very nice R4C it had a hum with bad audio distortion so I decided 
to investigate, whilst taking it apart I noticed that if I touched the noise 
blanker the hum would alter, I removed the NB board and the hum was still 
there, I found eventually that the audio transistor had desoldered itself, do 
they really run that hot? so I resolded the wires, now the radio does not work 
anything like as well and has a high amount of white noise, has that audio 
transistor died and if so where do I get a new one, is there an equivalent for 
that power transistor?
73, Max M0GHQ



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4C Hum and audio transistor

[Paul Christensen]

Max,

I'll get crucified for saying this, but that class A transistor stage was 
poorly designed -- and I think we can dispense with the "but they didn't have 
cost-effective transistor technology back thirty years ago" as an excuse.  A 
two-transistor complementary-symmetry PP pair running class AB and a moderate 
amount of negative feedback would have sounded substantially better, and 
produced much less heat.  

As an example, look at the Marantz, Sansui, Kenwood, and other mid-fi Japanese 
audio amplifiers being produced during the same period.  Those designs, or a 
variant, could easily have been leveraged into the R-4C.  Eliminate the audio 
output transformer and tap the symmetry pair mid-point, then couple with 500+ 
uF of series coupling C.  I don't know what Drake's cost was for the audio 
output transformer, but I have to believe the production cost difference 
between the transformer and an extra audio output transistor, and surrounding 
passive parts would have been reasonably minimal.

I jettisoned the R-4C AF stage after the volume control and won't be going back.
 
Paul, W9AC
  - Original Message - 
  From: Max Cotton 
  To: drakelist@zerobeat.net 
  Sent: Wednesday, October 31, 2012 2:10 PM
  Subject: [Drakelist] R4C Hum and audio transistor


  I have a very nice R4C it had a hum with bad audio distortion so I decided to 
investigate, whilst taking it apart I noticed that if I touched the noise 
blanker the hum would alter, I removed the NB board and the hum was still 
there, I found eventually that the audio transistor had desoldered itself, do 
they really run that hot? so I resolded the wires, now the radio does not work 
anything like as well and has a high amount of white noise, has that audio 
transistor died and if so where do I get a new one, is there an equivalent for 
that power transistor?
  73, Max M0GHQ


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4C Interesting Find

[Paul Christensen]

Bill,

Interesting.  Same issue with the Drake 1A.  Sensitivity is affected by the 
quality of the antenna trimmer capacitor bonding to chassis ground.

Paul,   W9AC
  - Original Message - 
  From: Bill & Becky 
  To: drakelist@zerobeat.net 
  Sent: Saturday, September 01, 2012 7:44 PM
  Subject: [Drakelist] R4C Interesting Find


  My R4C seemed a bit poor in the sensitivity department so I had an idea to 
improve it. I aligned the R4C pretty well but it didn't seem very lively.

  So with the bottom chassis visible I took my screw driver and loosened/ 
tightend each screw twice on each side of the 4 rows of trimmer bracket ground. 
 Wow.what a difference in sensitivity mainly 160-20M and in between.  I 
estimate a  8-10 dB of more gain.  I learned this method of re-establishing 
grounds from a metallurgist(sp)ham neighbor who showed me what happens to two 
surfaces create a fine film a lose bonding with time. If the two metals are 
much different the faster the degradation.

  Your mileage may vary. I recommend all accessible screws and nuts...it 
can cure some pretty obscure problems and takes less than 15 minutes.  I had to 
recalibrate the S-meter because of the gain change. It should work on R4any 
receiveror any old boatanchor.

  Bill  KB9IV


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4B Transformer temp

[Paul Christensen]

It's normal for the R-4B power transformer to run hot.  And to Carl's point, 
the audio tube, running class A near the transformer adds even more heat.  

I really dislike cabinet heat and rather than use a fan, I went to the extreme 
last year and made several circuit conversions.  The first phase involved 
replacing the power transformer with the type found in the R-4C, then 
converting all 12.6v tubes to their 6.3V equivalents.  This was followed by the 
installation of the Sherwood PS-4 upgrade to further reduce heat by eliminating 
power-hungry resistive dividers.  The last phase involved complete removal and 
replacement of the class A audio stage with a discrete, audiophile-grade Class 
AB push-pull audio board.

After the mods, the R-4B is cool to the touch, like a Sherwood modified R-4C.  
This was an extensive experimental exercise and I don't recommend it as a 
casual upgrade. Probably with even a modest amount of air flow, the cabinet 
will run significantly cooler.

Paul, W9AC
  - Original Message - 
  From: gypsym...@aol.com 
  To: euge...@nni.com ; Drakelist@zerobeat.net 
  Sent: Monday, June 18, 2012 7:09 AM
  Subject: Re: [Drakelist] R4B Transformer temp




   euge...@nni.com writes:
R4B.  I
noticed that even  the transformer seemed very warm - virtually hot. 
  Probably the tube just to the right of it, a small fan on top of the case 
helps a lot.
  Carl WD8NHK  that's what I do with my R4


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C

[Paul Christensen]

Cliff,

The information on WB4HFN's website is a good place to start:

http://www.wb4hfn.com/DRAKE/DrakeArticles/PTO/Drake_PTO.htm

Paul, W9AC


-Original Message-
From: fofield 
To: drakelist 
Sent: Mon, Apr 30, 2012 2:14 pm
Subject: [Drakelist] R-4C


My tuning dial is not easy to turn..Not freewheeling by any means.
Any suggestions what to try before I take the PTO cover and everything 
else off if I dont have to? Thanks 73 Cliff



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] pan adapter

[Paul Christensen]

The Ensemble really is a cool little receiver.  Tony and the rest have 
done an

outstanding job!


For many years, I tried to order a Softrock kit, and now the Ensemble Tx/Rx. 
In every single instance, the kits have been unavailable with a "check back 
soon!" message.  I checked again today, and the status has not changed. 
Frustrating...


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] pan adapter

[Paul Christensen]

But..does it track with the tuning of the R-4C?
Why would ya want to tune 2 RX's at the same time?
73,
Lee


The preselector is the limiting factor as Garey pointed out.   The problem 
is worse on the lower bands, especially 160m.  You would need to tap ahead 
of the preselector -- essentially at the antenna terminal.  So, the antenna 
feed must be split with a simple 50/50 power divider, one side to the R-4, 
the other to the SDR receiver.  This is the same manner used by folks who 
use up-converting transceivers like the Ten Tec Omni 7, Icom 7700, 7800, 
etc.  Only, the sync issue between the R-4 and SDR receiver would be very 
difficult to solve since there's no computer interface on the R-4 to allow 
for tracking to the SDR receiver.


I cannot see a way to effectively use an SDR receiver as a panadapter with a 
Drake 4 or 7-line receiver.


Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Pointer knob lines

[Paul Christensen]

What suggestions does the group have on re-whitening the lines on the
pointer knobs? I was thinking of using model enamel and a toothpick, wiping
away any excess with qtips. Mike.


I've been using Liquid Paper "white out" in a ball-point pen package.  You 
squeeze the body of the pen as you roll ball-point along the engraved knob 
line.  Mess it up?  No problem.  Just start over.  Any overage is easily 
taken away after it dries in about one minute.  It looks great, stays bright 
white and doesn't yellow.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Sherwood Mods

[Paul Christensen]

"We have no problem discussing the modifications, certainly they
are HIS [Jim] radios to destroy as he sees fit, and I can keep mine as 
pristine as I choose."


Ouch, that one hurt, Garey.  I would hope that not everyone agrees a 
modified Drake can no longer be "pristine."  Apart from my near-complete 
wrecking-out of an R-4B, it's about as cosmetically restored to pristine as 
they come.  I do think if anyone on the group actually experienced my R-4B 
with its almost zero cabinet heat, 0.05 % THD/1kHz at 4-watts, flattened 
audio passband (+/- 1.0dB 50 Hz to 3.5 kHz), no hiss, no hum, no buzz, 
improved Fast AGC -- and inspected it for cosmetics, then maybe, just maybe 
they would change their mind!  Or not...


I'm almost feeling a need to replace the aluminum front panel and remove any 
reference to "Drake."  Kinda' like when a retail store closes and its 
corporate leadership obliterates any prior association to protect its brand!


Paul, W9AC


- Original Message - 
From: "Garey Barrell" 

To: "lee" 
Cc: 
Sent: Tuesday, January 03, 2012 12:31 PM
Subject: Re: [Drakelist] Sherwood Mods


Lee -

I understand what you are saying... I too am one that prefers to keep 
'vintage' gear, Drake or
otherwise, as it was! The quirks and shortcomings of these radios is 'who 
they are', and modifying

them changes them from 'vintage' to 'just another radio'.

When they were new, and Rob Sherwood and others suggested/made modifications 
to improve a function
that was omitted due to either cost or design decisions, and actually 
_improved_ it, the 'state of
the art' was advanced. A Sherwood R-4C was just about the best receiver _FOR 
CONTEST OPERATION_
available at any price at that time. For general use on the amateur bands, 
not so much. Yeah, once
every week or two you might have someone snuggle right up against you and 
the mods would make the
difference, but that was the exception. You could just turn on the amp and 
they'd move! :-)


Today, however, there ARE better receivers available, some even cheaper than 
a Sherwood R-4C, PLUS
digital frequency readout, computer control, and all sorts of other 
'features' that are of value to
a contest operator. Once again, even those 'features' are only really of 
benefit to a contest
station. Yes, it's fun setting them up, and then sitting back and watching 
the radio operate the
contest for you, but  :-) What was it that the QST article said some 
years ago?? Start your
station for a weekend contest, go to the beach or the mountains, and check 
when you get home to see

how you did in the contest!!

The example some have used of the braid ground lead on the PTO is an example 
of a 'field change'. If
you keep the gearbox rider bar clean, and use light oil in the ball bearing, 
you really don't NEED
the braid. But the braid makes the radio less susceptible to failure, so why 
not. The braid became

standard on late C-Line and all 7-Line PTOs.

I do NOT think we need a separate group to further segregate the Drake 
community. We have members
who feel as I do, and others like Jim(!) who just can't wait to take a 
soldering iron to a
previously unmolested radio!! :-) We have no problem discussing the 
modifications, certainly they
are HIS radios to destroy as he sees fit, and I can keep mine as pristine as 
I choose. I'm
interested in what he does, he tolerates my Luddism, and we get along just 
fine. At least until
now... Dividing our 'almost' always non-combative group seems 
counter-productive to me. Sharing
ideas, even wrong ones (!) is healthy! We ALL have a DELETE key if something 
REALLY bothers us


Full disclosure, the DrakeRadio group that I 'own' was 'inherited', and I 
agreed to take it on just
to keep it from dying. DrakeRadio is typically a little less busy than 
Drakelist, and when I see a
new call over there I tell them about Drakelist and suggest that they join 
both. I think most Drake

people are members of both groups.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



lee wrote:
This may be true but I can tell you I purchased a lot of new Drake gear 
from Drake dealers and when I ever talked to the factory regarding them, 
without naming names, it was expressed very clearly each and every time 
their/his disfavor of those mods. I happen to agree with those remarks. I 
would never consider them. In fact, I am thinking of starting a new Drake 
reflector or wish someone else would open one where it would be forbidden 
to discuss foreign mods except for those really needed because of lack of 
old parts. I personally consider the mods offensive and consider a radio 
with these mods no longer a Drake product.
I know not everyone agrees with me, but I know some may agree with me. Don’t 
get me wrong. If you own a radio, I believe you can do anything you want 
with it and you can believe anything you want about your mods. I just don’t 
agree with this philosophy at all. I am not trying 

Re: [Drakelist] R4C Sherwood mods

[Paul Christensen]

Most of Parts for the Sherwood MODS are not cheap...the relays alone
for the filter swich board are $20 each + and you need several.
Also, you need to be pretty creative to get it all in there...pretty
tight in places.


Yes, a tight fit, put perfectly manageable.  Keep in mind that the Teledyne 
relays used for the filter switch are designed for RF applications and 
hence, the high cost.  The entire relay board assembly was designed to 
eliminate filter leakage and "blow-by."  Take a look at the Sherwood 
ultimate filter rejection spec and it's easily to see where the buyer's 
money is going.


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4c sherwood moods

[Paul Christensen]

Every now & then...I will ONLY use my C line and L-4B for a whole week 
end...


Lee,

That's a great idea since it gives you the opportunity to re-visit the older 
technology and compare notes against recent designs.  I have no issues with 
well-designed and implemented mods that serve an overarching purpose.  The 
Sherwood mods accomplish that.  Moreover, I keep respect alive by ensuring 
that cosmetically, they are as perfect as possible.  I have to thank the 
many folks who have provided those resources.  At one time or another, 
they've been the recipient of my business.


Both my R-4C and R-4B are heavily modified.  The R-4B may not even be 
recognizable under the chassis to most folks here.  But I started with a 
purpose and designed for it.  The changes meet my operating goals and were 
not meant to appeal to all Drake users.


Folks who have used a Sherwood-modified Drake have every right to express 
their opinion -- but seemingly, several users have not tried the mods and 
have based their opinion on perception and not reality.  Another a group of 
users seem to resent that some owners have attained the aptitude to either 
install and/or design their own mods.  This attitude seems even stronger 
among Collins owners.  Now, that's *my* perception and may not be reality!


Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4C PTO Brass Gears replacement

[Paul Christensen]

Hi Rich,

I agree with you that the metalNylon assemblies seem to have a smoother 
feeling with less sloppiness.  I don't know if the all-Nylon gears degrade 
over time or if they came that way from Drake.


I changed a set to metal/Nylon gears back last spring.  I was first going to 
attempt a change of gears, but I decided to simply swap out entire PTO 
assemblies from a late C line that was in less than average cosmetic 
condition.  That's a very easy job.  Just a few wires are unsoldered, three 
screws removed, and the whole PTO assembly with dials comes out.  No 
calibration, no worry about gears meshing and tracking properly, etc.  After 
changing out one assembly and learning from it, another can be done in just 
a couple minutes.


Paul, W9AC

- Original Message - 
From: "Rich Hallman - N7TR" 

To: 
Sent: Saturday, December 17, 2011 11:53 AM
Subject: [Drakelist] R4C PTO Brass Gears replacement



Ive had my R4C PTO rebuilt about 8 months ago and the PTO tuning felt
great.  Before the rebuild it would stick and  would have different
tightness as I tuned.

I hadn't used the rig for a few months and turned it on last night and I
have the same issue again.  Wanted to know if anyone changed out the
nylon gears for the brass set?  I think the nylon gears keep swelling on
me.  And yes, the oil was removed during the first rebuild.

Also...does anyone have a set of brass gears or an old broke PTO with a
set of brass gears on it that they would like to sell.

Thanks...
Rich

Rich N7TR
ex KI3V, N3AMK, WB3JOV
www.n7tr.com
Telnet: dxc.n7tr.com N7TR DXCluster



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] SPR-4 Vs R8

[Paul Christensen]

Any significant performance or operating differences between the R-8A and 
R-8B?


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Michael A. Kelly" 
Cc: 
Sent: Wednesday, November 23, 2011 3:54 PM
Subject: Re: [Drakelist] SPR-4 Vs R8



Michael -

I've never owned an SPR-4, but it would be hard to beat my R-8A.  6 kHz IF 
filter, Synchronous AM detector and Passband Tuner make a pretty good 
receiver.  A wider IF might sound better for music, but much less 
resistance to QRM.


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Michael A. Kelly wrote:

Just curious - for AM .. which is a better performer specifically with
the AM Broadcast band in mind?

Thanks,

Michael N4MAK



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] OT a failure mode of solid state electronics

[Paul Christensen]

A consequence of RoHS compliance.  The problem has already been documented 
with N8LP's LP-100 display board (PLED version).  Display segments begin 
failing, one-by-one until the display becomes very difficult to read.  Not 
sure if there's been any recent developments concerning chemical or process 
improvements to lessen the severity of the "whiskering."


I have spools of Kester clean solder, and a spool with 2% silver -- neither 
of them flow very well.  I'm inclined to stay with Kester 44 60/40 solder 
from this point forward.


Paul, W9AC

- Original Message - 
From: "Bob Spooner" 

To: "'Ron'" ; 
Sent: Tuesday, November 01, 2011 8:47 AM
Subject: Re: [Drakelist] OT a failure mode of solid state electronics



Ron,

Vintage radios were made with regular leaded solder so they don't have 
that

problem (unless you repair them with lead free solder.) It's the new rigs
that I'm concerned about. Tin whisker growth under surface mount 
components

would be very difficult to detect and remove. So keep your vintage Drake
radios operational and you won't be without a rig if the new one fails.

73,
Bob AD3K

-Original Message-
From: drakelist-boun...@zerobeat.net 
[mailto:drakelist-boun...@zerobeat.net]

On Behalf Of Ron
Sent: Monday, October 31, 2011 6:46 PM
To: drakelist@zerobeat.net
Subject: [Drakelist] OT a failure mode of solid state electronics

All,
I was tooling around the web and ran into this video and document.  For
those unfamiliar, the new lead free solder often has a higher tin content
and can causes tin whisker growth issues.   Who knows when it might strike
your beloved solid state or hybrid vintage radio.  Maybe we should all
return to hollow state  :-)

http://www.vintage-radio.info/whiskers/

Totally amazing IMO.

73,
Ron WD8SBB

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] T-4XC Unstable PTO (I think)

[Paul Christensen]

You would not be able to see a few tens of Hertz change on a scope.


One method of observing small changes in frequency (and phase) is to utilize 
the X-Y function on a scope to display a Lissajous pattern.  I have no doubt 
Garey has done this in the past.  For others, one simply takes a 
known-stable RF generator and feed it into Channel 1 of the scope.  The PTO 
output is fed into Channel 2.  The scope time base is set to "X-Y" mode.


Next, the stable generator amplitude can be set to approximately equal that 
of the PTO.  Amplitude equality does not have to be very precise.  As 
frequency changes, so will phase.  Two in phase and on-frequency signals 
will show on the scope's displays as a straight 45 degree line.  As the PTO 
changes frequency, the line will turn into an oblong loop and continuing 
further, a perfect circle at 90 degrees of phase difference, then it will 
show as a straight line again but at the 135 and 315 degree points on the 
scope's display.


With the Lissajous method, even the slightest change in frequency between 
two sources can be displayed on a scope.


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Robert Fish" 
Cc: 
Sent: Wednesday, October 26, 2011 12:21 PM
Subject: Re: [Drakelist] T-4XC Unstable PTO (I think)



Bob -

You would not be able to see a few tens of Hertz change on a scope.  The 
warbling of the calibrator signal is often a power supply thing, C179 on 
the Calibrator board.  Since it's intermittent, it's more likely a bad 
ground, I'd suggest 'exercising' the Calibrator plug by moving the board 
up and down a bit.   DeoxIT on the connector pins wouldn't hurt.


There are two primary causes for PTO instability.  One has been going on 
for years, which is the intermittent grounding of the PTO slug and drive 
screw.  The grounding path(s) are through the drive follower riding on the 
chrome rider bar at the top of the gearbox, and the ball bearings in the 
front plate.  Hardened grease forms little 'chunks' that break the path 
through the ball bearings, causing frequency jitter when tuned.  Usually 
not a problem when tuning is stopped.  Drake offered a 'fix' of a small 
piece of wire braid soldered from the drive follower to the side wall of 
the gearbox.  The field change is on the CD in the MISC directory.


The second cause seems to be happening more often lately,  and is the 
breakdown of one or more of the capacitors in the frequency determining 
circuit of the PTO.  There are a couple of 'common' culprits, depending 
upon which of the 17 versions of PTO that you have.  You should be able to 
see the jitter on a counter, the changes are tens of Hz if you can hear 
them.  Freeze spray can help to isolate the defective cap(s), but not 
always.  In the C-Line PTO C157 and/or C203, which may be either two 45 pF 
NP0 tubular ceramic caps or a single 90 pF is the most common 
troublemaker.  It's best to measure the value of the existing cap and then 
choose a replacement as close as possible.  C158 and C159 are selected at 
test to compensate for variations of C157 for linearity, and if you select 
C157 accurately linearity doesn't seem to be impacted.


Less likely causes are a bad FET transistor Q8, or a bad Zener diode CR6. 
I have seen one case of a leaky C151.


The trials and tribulations of PTO repair are in the archives about a 
month ago on this list and on DrakeRadio.


--
73, Garey - K4OAH
St Charles, IL

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Robert Fish wrote:

Hi Guys,

I have been ignoring an issue with my T-4XC until recently. When I use 
the R-4C PTO to control the receiver it seems to work fine.
When I use the T-4XC PTO to control the receiver I get sort of a chirpy, 
jumping around of the cw signal I am trying to copy. Both units
work fine in transceive using the R-4C PTO, which is the way I have been 
using them. But with the recent DX expeditions (T32C, TX7M)
running split, I have been having to use the C-line as separates to work 
them. I have had some success working them, but heaven knows what my 
signal sounds like.


I have been putting off fixing this problem as I felt it was probably the 
PTO and I haven't been in the mood for performing major surgery lately.
I decided to get off my arse and do something about it yesterday. So, I 
got out the scope and took a look at the T-4XC PTO output while it was 
controlling the R-4C.
It seems stable. So I looked at the Plate of V-8 with the scope, I have a 
composite signal (PTO, Xtal Osc.) it looks solid as a rock. So then I 
looked at the injection signal
right at the jack on the back of the T-4XC and once again, I can hear a 
cw signal I tuned in on the R-4C jumping all over the place, while I'm 
looking at a rock solid injection sig
leaving the T-4XC. I switch back to the R-4C PTO and the jumping around 
stops, the receiver copies the same cw sig with stability.


What am I missing here? It is hard to fix something when it seems

Re: [Drakelist] T4XB Question

[Paul Christensen]

Bob,

Good feedback.  In retrospect, I probably should have gone with either a 100 
or 150-watt iron with the high mass shaft ahead of the tip.  The perceived 
size of these irons can be deceiving.  I was very surprised by the weight 
and size of the 200-watt Hexacon iron.  It's really too large and heavy to 
manipulate into small areas, especially where a lot of circuit wiring comes 
in proximity to the chassis can tabs.


Paul, W9AC

- Original Message - 
From: "Bob Spooner" 
To: "'Richard Knoppow'" <1oldle...@ix.netcom.com>; "'Paul Christensen'" 
; 

Sent: Tuesday, October 25, 2011 3:47 PM
Subject: RE: [Drakelist] T4XB Question


The requirement for removing filter cap cans is to move a lot of heat 
energy

into the solder joint in a short period of time, so that the joint
temperature get's high enough fast enough to not heat up everything else
around it as well. (Think PL-259 braid soldering.) This can be done one of
two ways, either with a high mass low-wattage soldering iron (low rate of
energy input, high heat capacity) or with a high-wattage soldering gun 
(low

heat capacity, high rate of energy input.) The heat transfer is driven by
the temperature difference. If too small an iron is used, the tip
temperature will decrease too rapidly to do the job.

73,
Bob AD3K

-Original Message-
From: drakelist-boun...@zerobeat.net 
[mailto:drakelist-boun...@zerobeat.net]

On Behalf Of Richard Knoppow
Sent: Tuesday, October 25, 2011 3:10 PM
To: Paul Christensen; Drakelist@zerobeat.net
Subject: Re: [Drakelist] T4XB Question


- Original Message - 
From: "Paul Christensen" 

To: 
Sent: Tuesday, October 25, 2011 11:36 AM
Subject: Re: [Drakelist] T4XB Question



 I replaced the three-section electrolytic in my R-4 with
no major
problems (that Drake chassis is a huge heat sink - make
sure you're
using a big iron/gun).


After trying to tackle the filter cap removal from my
Drake 1A, I began looking for 200-watt soldering irons.  I
was (and still am) in shock over the price of new,
high-wattage irons.  I finally found a used, 40+ year old
200-watt Hexacon iron, and it was still nearly $100.  Best
as I can figure, the price of new Hexacon and American
Beauty irons is held up by demand from commercial sheet
metal workers.

Paul, W9AC


You might try local swap meets or junk shops. I've
bought several large old soldering irons at such places for
a few dollars. You may have to replace the tips but usually
you can just file them down a little and re-tin them. I have
not looked on ebay for them but its another possibility. Two
of my large irons are American Beauty brand and I think the
other is Esico both once top brands. The mass of the tip may
be more important than the wattage. Modern irons have very
little mass so are cooled quickly, for working on old
equipment one needs a high mass iron.


--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] T4XB Question

[Paul Christensen]

 I replaced the three-section electrolytic in my R-4 with no major
problems (that Drake chassis is a huge heat sink - make sure you're
using a big iron/gun).


After trying to tackle the filter cap removal from my Drake 1A, I began 
looking for 200-watt soldering irons.  I was (and still am) in shock over 
the price of new, high-wattage irons.  I finally found a used, 40+ year old 
200-watt Hexacon iron, and it was still nearly $100.  Best as I can figure, 
the price of new Hexacon and American Beauty irons is held up by demand from 
commercial sheet metal workers.


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] [DrakeRadio] Re-capping an R-4

[Paul Christensen]

Yeah, we used Freon TF in spray cans at NASA 40 years ago.


Garey,

This is what happens when I'm all caught up with my chores and it's raining 
the entire weekend.  Turns out that Caig makes a Freon TF substitute called 
Caikleen NF.  Seems to have many of the same properties and might be worth 
adding to the shop solvent cabinet.


http://store.caig.com/s.nl/ctype.KB/it.I/id.394/KB.218/.f

Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] [DrakeRadio] Re-capping an R-4

[Paul Christensen]

Garey,

Your purchase is definitely the better value although I'm not sure if DeOxit 
has a shelf life?  Come to think of it, is there a shelf life for most of 
these products?  I have cleaners on  the bench that are now 15+ years old!



Where do you find the Chemtronic stuff.


For the past 20 years, I've been purchasing the Chemtronics cleaners & 
lubricants through Mouser and Newark.  The first Chemtronics product I used 
as a teenager was "Tune-O-Wash," sill made today but is now EPA compliant. 
That product worked better than most for electro-mechanical TV tuners and 
would not de-tune the circuits.  Getting a bit off topic here, but I once 
tried the RadioShack tuner cleaner/lubricant and never could get a tuner 
back in alignment.  God only knows what semi-conductive fluid they used. 
This was in the mid '70s.


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: 
Cc: "Paul Christensen" 
Sent: Saturday, October 08, 2011 4:27 PM
Subject: Re: [DrakeRadio] Re-capping an R-4



This is what I use.

*http://tinyurl.com/45yqnfd*

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:

And here's the same 100% solution the D100S spray:

http://tinyurl.com/3jqhxk2

Paul, W9AC



   - Original Message -
   From: Paul Christensen
   To: drakera...@yahoogroups.com
   Sent: Saturday, October 08, 2011 2:16 PM
   Subject: Re: [DrakeRadio] Re-capping an R-4



   Don,

   I recently made a purchase of the 2.4 ml bottle for $15 through 
Amazon. I combined it with some other solvents and shipping was free.


   I've stopped using DeOxit on wafer switches and now pretty much limit 
its use to pots/faders. I have not had any trouble with DeOxit on wafer 
switches, but I've seen evidence of the dirt/dust it attracts over time.


   So now, I'm using several fast-evaporating Chemtronics sprays and the 
results have been just as good as DeOxit on open switches. For example, I 
recently purchased a Collins 75S-3C and the band switch was so 
intermittent, I thought it was broken. I used the Chemtronics spray 
developed for switch contacts and the bandswitch operates like new.


   Paul, W9AC

   - Original Message -
   From: Don Cunningham
   To: drakera...@yahoogroups.com
   Sent: Saturday, October 08, 2011 2:01 PM
   Subject: Re: [DrakeRadio] Re-capping an R-4

   Garey,
   Where did you find the D100L DeOxit?? I need to get a bottle (even if 
it hurts) as I am getting stocked up to do a BUNCH of rigs this winter. 
Hope my ambition holds out. I've been helping Hayseed's sales, HI.

   73,
   Don, WB5HAK




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Changing crystal frequency

[Paul Christensen]

>What can REALLY be vexing, though, is when the crystal(s) used in 
>carrier-generating oscillator frequencies "migrate": I once had an SB-102 
>transceiver that sounded very tinny & nasal-sounding on LSB only---much to my 
>chagrin, THAT carrier generating crystal had shifted just enough so as to put 
>a goodly portion of my signal REMOVED from the passband of the IF filter!"

Same issue I have with my Collins 75S-3C.  LSB audio in the fixed BFO position 
does not have the same audio passband characteristics as USB.  Even small 
changes (e.g., 50 Hz) can have a profound effect on the tone of the recovered 
audio.  Unlike the R-4C where its two BFO crystals operate at 10x that of a 455 
kHz BFO, the 75S-3 has no variable compensating caps to adjust the crystals' 
operating frequency.  However, when switched to variable BFO mode, all is well 
and the audio tone can be adjusted with the BFO control.  INRAD sells 
replacement BFO crystals for the 75S-3, so I'll likely try those and see if 
that improves the fixed BFO audio.

Paul, W9AC
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4B PTO indicator...

[Paul Christensen]

Revesing the leads is about as much work as replacing the lamp and I 
am not sure it works.


I swapped my neon lamp leads on the PCB, not at the panel.  About a minute 
of easy soldering and well worth the try.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4B PTO indicator...

[Paul Christensen]

> 1) Replace the lamp with a fresh one and wait for it to drift upward (that 
> could buy you a year or many years).
> 2) Reduce the value of the dropping resistor and take a chance that the 
> transistor won't break down under the extra voltage present.
> 3) Upgrade the transistor to a high voltage rating device and get rid of the 
> dropping resistor entirely (permanent fix and what Drake should have done in 
> my opinion).

As a "Hail Mary Pass," a fourth option may work as it did on my R-4B.  Simply 
reverse the neon lamp leads.  When a DC voltage is used on a neon lamp, only 
one pole is active with light.  For whatever reason, going to the unused pole 
may cause re-establish proper firing.  

Mine was intermittent at normal utility voltage (125V here in my area) but I 
wanted to begin using CL-90 voltage dropping Thermistors to bring line voltage 
down to 117V from 125V.  I couldn't get the neon lamp to fire at all with 117V, 
but simply reversing the lamp leads allowed it to fire down to 110V.  I won't 
even begin to try and explain the chemistry and physics that made it happen but 
it's certainly worth a try.

Paul, W9AC

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")

[Paul Christensen]

Steve,

I would make that decision once you get to the root cause of the PTO 
instability.  Between now and then if you want to try a Polystyrene cap to 
simply rule out the dog-bone cap, I think it's fine.  Both Polystyrene and 
silver mica are both highly temperature stable.

Keep in mind that the self inductance of a Polystyrene cap is typically greater 
than that of a comparable silver mica type.  Also, Polystyrene caps typically 
have a red tracer on one end.  This end is connected to the outer foil.  Why is 
this important?  In applications where one end is attached to circuit ground or 
near +Vcc potential, the capacitor will be significantly more stable as the 
result of distributed capacity effects (e.g., a grounded coil cover).  The 
tracer does not imply that it is a polarized cap -- it only distinguishes the 
end connected to the outer foil.

Analog Devices has produced a nice summary of capacitor dielectric types:

http://www.analog.com/library/analogDialogue/Anniversary/21.html

Paul, W9AC
  - Original Message - 
  From: Steve Wedge 
  To: drakelist@zerobeat.net 
  Sent: Sunday, July 31, 2011 2:49 PM
  Subject: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")


  I'm looking at options for replacing the "dogbone" 3000 pF SM cap in the PTO. 
 I've long heard the polystyrene caps are stable and of high quality.

  What's your opinion of using a polystyrene cap in place of the SM unit at 
C146?


  Steve Wedge, W1ES/4

  "I can't complain, but sometimes I still do."
  - Joe Walsh

  If the above message appears, it came from Steve's Son of Laptop!


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4A PTO: Confirmed it's the PTO.

[Paul Christensen]

The 78L10 is only 39-cents ea. in small quantities through Mouser.  I had 
always assumed that a Zener with current limiting resistor or in the 
alternative, a Zener with pass transistor would produce a quieter output 
than a monolithic regulator?


So, is it possible that a 78L10 may be more stable as a PTO regulator, but 
may require more in/out conditioning than a Zener?   The Fairchild 78L10 
datasheet recommends a 0.33 uF bypass on the input leg, and 0.1 uF bypass on 
the output.


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Dennis Monticelli" 
Cc: 
Sent: Saturday, July 30, 2011 2:21 PM
Subject: Re: [Drakelist] R-4A PTO: Confirmed it's the PTO.


Which is why subbing the Zener is the FIRST thing we check, after making 
sure the spring is in place!!  :-)


Is a three-terminal regulator such as a 78LO10 ?  a better choice??

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Dennis Monticelli wrote:
I know from my experience in the semiconductor business that zeners 
(especially those from a prior era) are notoriously noisy and can become 
outright unstable to varying degrees.  You will not see this with a DVM 
or other averaging type instrument.  You should put a scope on the zener 
and turn up the gain as high as the scope will go while setting the time 
base for anywhere from 1 to 100ms/div.  Make sure your scope ground 
connection is right at the zener to keep stray pickup at a minimum.  If 
it is unstable you will see the voltage jumping around in discrete steps. 
A typical zener will just exhibit "white" noise which looks like tall 
grass on the CRT.  Both the discrete steps and the white noise will 
modulate the PTO.  The steps manifest as annoying random freq shifts 
while the white noise just adds to the noise sidebands of the oscillator. 
The discrete jumps in zener voltage are understood in the physics but 
unless folks are truly interested in that stuff I won't go into it here.
Not to scold the Drake design team (whom I respect) and maybe mostly 
because I witnessed how the sausage is actually made, but I would NEVER 
design a zener into a circuit as noise sensitive as an oscillator, mixer 
or preamp.   I designed and built a homebrew antenna noise bridge.  Guess 
what I used as the broadband noise source?

Dennis AE6C

On Fri, Jul 29, 2011 at 3:25 PM, Steve Wedge > wrote:


Well, it has been a long, strange trip here.

Just finished a little experiment with the PTO and my K3.  First of 
all, the K3 is deaf as a
post at 4.9 MHz ;-) but I did get enough of a signal through a scope 
probe hooked to the PTO

output to confirm that it's the PTO that is shifting frequency.

Having confirmed that, my next step will be replacing the 3000 pF and 
the zener - even though
I'm fairly convinced the zener is okay (alright - I'll replace the 
3000 pF first...).


I have a sneaking suspicion that this may be one of the S.A.T. caps. 
If so, it's going to be

interesting since I no longer have a capacitance meter.

Steve Wedge, W1ES/4

"I can't complain, but sometimes I still do."
- Joe Walsh

If the above message appears, it came from Steve's Son of Laptop!
- Original Message - From: "Garey Barrell" 

>
To: "Steve Wedge" >

Cc: mailto:drakelist@zerobeat.net>>
Sent: Friday, July 29, 2011 3:21 PM
Subject: Re: [Drakelist] R-4A PTO: It wasn't the transistors


Steve -

Yes, the PreMixer signal (V8) (BAND minus PTO) is the one that is 
piped back and forth

between the two units.

All you have to do is listen to the PTO signal itself on a 
separate receiver.  "0" on the
dial = 5.455 MHz, "500" = 4.955.  The BFO crystal is 5.595 MHz. 
The BFO is a tube, V3,
which I believe we swapped way back towards the beginning of this 
odyssey!!  I also
thought you had put a counter on the PTO, but I guess that's 
another 'project'.  :-)   I
typically have three or four of these eMail projects going at one 
time, which is why I
like to keep the entire thread together.  Makes it easier to go 
back occasionally just to

review just what path got us 'here'!  :-)

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
http://www.k4oah.com/>>


Steve Wedge wrote:

You know, Garey, I've been thinking about the xtal 
oscillator.  It would have to be
part that doesn't get bandswitched - which would include THAT 
transistor.


When the T-4X controls the frequency, it sounds great and 
never jumps frequency.  In
looking at the schematic, I have been aware that the two 
solid-state oscillators (PTO
and LO for the band) get mixed in V8 (IIRC) and that 

Re: [Drakelist] R-4A PTO: It wasn't the transistors (entirely)

[Paul Christensen]

Eddy,

Within a short period of time, the PTO is receiving sufficient radiated heat 
from the transformer and depending on the model of R4, either the AF output 
tube or Class A transistor.


I recently went in the other direction to remove as much heat as possible 
through the elimination of passive voltage dividers and installation of 
push-pull AF amps in the R-4B and R-4C.


I suppose someone could install a pilot lamp in the PTO as you suggest and 
then thermostatically turn it off above a predetermined temperature 
threshold.  As it is, the PTOs on my B and C series receivers have no 
detectable drift from start-up, and are linear within the 500 kHz spread +/- 
500 Hz from end to end.


Paul, W9AC

- Original Message - 
From: "Eddy Swynar" 

To: "Richard Knoppow" <1oldle...@ix.netcom.com>
Cc: 
Sent: Friday, July 29, 2011 1:28 PM
Subject: Re: [Drakelist] R-4A PTO: It wasn't the transistors (entirely)



Hi Richard,

I once went so far as to even contemplate the logistics of installing a 
small pilot bulb inside the PTO can to act as a "heater," with hopes that 
it might afford the circuitry a modicum of thermal stability (much like a 
crystal oven, if you will)...


The original plan was to have a feedthrough capacitor mounted in the can, 
with the bulb attached to it & the inside of the shield---the voltage to 
light it would have come from a "tap" to a convenient tube heater pin.


I never followed through on it, because of the fact that so many thousands 
of other Drake PTOs were apparently not ailing from what was afflicting 
mine---so why would mine be different...? Besides, space inside that PTO 
can is at a premium, & I was worried about the detrimental effects all the 
extra wiring of the bulb might have upon the PTO's function in terms of 
calibration, linearity, etc.


~73~ de Eddy VE3CUI - VE3XZ


***


On 2011-07-29, at 1:17 PM, Richard Knoppow wrote:



- Original Message - From: "Eddy Swynar" 
To: "Curt Nixon" 
Cc: 
Sent: Friday, July 29, 2011 9:54 AM
Subject: Re: [Drakelist] R-4A PTO: It wasn't the transistors (entirely)

   I have so far not had this problem any of my drake gear so I don't 
have direct experience trouble shooting it. Since so much of the PTO has 
been investigated without success I wonder if the problem could be 
external to the PTO. Either another oscillator or something after the PTO 
that is affecting it. I have no specific suggestions other than 
monitoring the PTO output with a receiver to make sure that is what is 
varying. Probably so but its worth being sure. Also, if it seems to be 
heat sensitive it may be possible to use a low power soldering iron to 
selectively heat compenents. I find a heat gun is too diffuse, it heats 
everything. Freeze mist is evidently hard to find now (I think it was 
Freon) but canned air works if the can is held upside down.
   Have you examined the coil to see if there is a loose turn? I know 
this is grasping at straws.
   Everything else I can think of has already been tried. It is so 
frustrating to trouble shoot something where all the parts are good but 
the thing doesn't work.



--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4A PTO - transistors substituted?

[Paul Christensen]

Or even a 2N.  Between the 2N3858, 2N3904, and 2N, the fT / GBP, 
hFE, and C in/out parameters are reasonably identical.  Probably the biggest 
variant will be the hfe value across samples, but I agree with Garey to give 
it a shot.  The PTO is only running at 5 MHz.


During college, I worked for an engineer who's philosophy was to replace 
with "2NAnyThing" that worked.  He certainly knew the widely different 
transistor parameters, but his point was that in many general purpose 
switching, amplification and oscillating circuits, "2NAnyThing" is often an 
adequate substitute, taking into account the need to watch for NPN, PNP, 
FET, etc. configurations.


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Steve Wedge" 
Cc: 
Sent: Sunday, July 24, 2011 2:45 PM
Subject: Re: [Drakelist] R-4A PTO - transistors substituted?



Steve -

I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in 
the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. 
No other changes required with either oscillator transistor.  The '3858 is 
just about extinct, but the 2N706 is still a common transistor.


Defective transistors have definitely been known to cause the kind of 
frequency changes you're seeing.  So while they may even be a 'later' 
modification than factory built, and may even be a suitable substitute, 
they can still fail just like the originals.  By the way, if you look at 
the PTO schematic, the FSK 'shift' terminal is connected to the output of 
the oscillator stage.  This allowed you to  _SHIFT_  the PTO frequency by 
up to 850 Hz by adding a cap from this terminal to ground.  So variations 
in the Buffer transistor CAN dither the frequency.  And yes, it does.


I think transistors were about the third thing down on the list once you 
get through the lubrication, mechanical and ground faults.


I know you said you were short on components, but '706s are cheap from 
Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors 
you could try them just to see.  They may not work perfectly, but if the 
PTO becomes stable you'll know.  Watch the basing on whatever transistors 
you use.  Seems like they are all different these days!


73, Garey - K4OAH
Glen Allen, VA




Steve Wedge wrote:
Looking at the transistors in this PTO, I'm 99.9% sure someone replaced 
them: they are both marked "NSRS / 2018", with the / being a line break.
I'm sort of thinking that Drake used different parts for the oscillator 
and buffer for a good reason.  Aside from this maddening 
frequency-shifting and crummy audio, the frequency calibration is still 
good.  What are the chances that using the "wrong" transistors could be 
the source of all this grief?


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] PTO Question and Drake 4C Questions

[Paul Christensen]

> Thanks for the PTO advice. I do recall hearing that the C line had a nylon 
> gear version and a metal gear version.  I think the metal gears were on later 
> builds??  I suppose there is no real way to tell without opening the cabinet 
> and looking inside.  

Operationally, I don't notice a difference but I much prefer the feel of the 
metal geared PTOs in the C Line.  The all-Nylon assemblies seem a bit sloppy 
during quick rotation.  But that does not affect the drive to slug, only the 
dial gears.  

> On the PTO, you said 'regular motor oil... is fine on the bearings".  So it 
> sounds like the Drake PTO is not greased up like the Collins PTO, just some 
> oil on soem bearings.  Are those just nylon or plastic sleeve bearings or an 
> actual bearing?  

You'll probably get many recommedations on this one.  I've recently used Daven 
oil on the worm drive and Lubriplate on the ball bearing raceway.  Since you'll 
likely not find Daven oil, it's similar in substance to what watch repair 
shops.  Being a Daven product from the days when broadcast consoles used ladder 
attenuators, the oil helps to preserve electrical conductivity.

> I don't own a C line yet as I am just starting to pursue one. I want to get a 
> late model setup and eventually acquire the full station except the 
> transverters and converters.   I've got a lead on a local one that hasn't 
> been used since 1994. Seller emailed some photos and I'm awaiting answers to 
> some questions about filters, extra crystals, crystal and filter covers, 
> corrosion, serial numbers, etc.. 

I think once you're up around the 26,500 serial number, you're probably okay 
with the metal gears but you need to ask the owner.  That's the only reason why 
I would pursue a late production R-4C.  If you proceed with Sherwood mods or 
other customization, it doesn't make much sense to hold out for a 29K+ unit 
unless you want to preserve it intact for historical preservation purposes.  
Both my B and C lines are heavily modified around the first mixer, power 
supply, and everything changed from the product detector to the headphone jack. 
 I doubt I would do this to a mint receiver.  I took average looking equipment 
and made them mint through new knobs, dial lenses, VFO knob with inlay, cabinet 
screws, painting by Hartzell, etc.  It does not take much to make a 
cosmetically mint receiver with all the recourses available.

> If you have a lead on a nice later model C line I'd appreciate hearing about 
> it.  

I think there's a nice one on the big auction place right now with many of the 
Sherwood mods.

Paul, W9AC___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Product Detector Low-Pass Filter

[Paul Christensen]

Had a few hours to kill this afternoon.  I added an 8-pole Chebyshev filter 
between the Shewood PD-4 product detector and the AF amp.  The new board 
kills what's left of any BFO leakage through the Sherwood product detector. 
Clean audio consistent with the SM0VPO audio board and there's no trace of 
ringing owing to the Chebyshev design.


The filter comes from Elecraft.  It's their model K3DF and is used to modify 
early K3s that had an 8 kHz spurious leak on the DSP board.  Two channels 
are included, 4-poles each.  I simply cascaded the sections to achieve 
8-poles of filtering.


The K3DF board is very small and contains all SMD components.  This helps to 
minimize RF and other induced noise.  A single low-noise quad op-amp is used 
as an active low-pass filter.  The only changes required were the addition 
of a 78L08 regulator, decoupled and fed from the Sherwood power supply 
board, and a pair of 50K metal film resistors to bias the input at 1/2 the 
+8 Vcc voltage.   The upper filter cutoff is about 4 kHz and the low-end is 
nearly at DC.  Since it is connected directly after the product detector, AM 
reception is not affected.


Cost is $40 + shipping through Elecraft.

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Alignment Instructions

[Paul Christensen]

Ahhh...minor typo in the manual at Sec. 5-7.  There's a wide space between 
"T1" and another "1" that my eye didn't catch!   Tnx, Garey.


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Paul Christensen" 
Cc: 
Sent: Saturday, July 09, 2011 11:58 AM
Subject: Re: [Drakelist] R-4C Alignment Instructions



Paul -

T11

Yes

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:
Clarification of the Drake R-4C alignment portion of the manual on p. 5-2 
would be most appreciative:


1) 50 kHz BFO AND IF ALIGNMENT.

Instructions call for adjusting T1 to 50 kHz (+/- 25 Hz).  However, T1 is 
part of the four-gang preselector rack.  Since T1 varies with the 
preselctor position, how is this accomplished?


2) 5-9. FILTER MATCH ALIGNMENT.

Instructions call for finding the Xtal cal signal on the 80m band, then 
tune up until 20 dB S-meter reduction occurs.  Then peak T5.  The problem 
with this is that in AM mode, the peak of the cal signal is many kHz 
wide.  Can I just find the middle of the passband by temporarily 
switching to SSB and tune for zero-beat -- and then switch back to AM and 
move the VFO upwards until 20 dB reduction occurs at which point T5 is 
then peaked?


Tnx!

Paul, W9AC







___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Alignment Instructions

[Paul Christensen]

Clarification of the Drake R-4C alignment portion of the manual on p. 5-2 
would be most appreciative:


1) 50 kHz BFO AND IF ALIGNMENT.

Instructions call for adjusting T1 to 50 kHz (+/- 25 Hz).  However, T1 is 
part of the four-gang preselector rack.  Since T1 varies with the preselctor 
position, how is this accomplished?


2) 5-9. FILTER MATCH ALIGNMENT.

Instructions call for finding the Xtal cal signal on the 80m band, then tune 
up until 20 dB S-meter reduction occurs.  Then peak T5.  The problem with 
this is that in AM mode, the peak of the cal signal is many kHz wide.  Can I 
just find the middle of the passband by temporarily switching to SSB and 
tune for zero-beat -- and then switch back to AM and move the VFO upwards 
until 20 dB reduction occurs at which point T5 is then peaked?


Tnx!

Paul, W9AC







___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] D104 and TR7

[Paul Christensen]

Note: if the high level input pin is used, the load is 470K + the low 
level

impedance. I use 470K for the series resitor, for a total of around a meg.


Jim, Excellent point.

If you were going to use the D104 with a modern DSP-based transceiver, I 
would have suggested gutting the Astatic preamp and replace it with one 
of the FET buffer circuits shown on my QRZ.com page.


I should think that the resistor method would work with just about any rig 
that

will accept a low-Z dymanic mic.


Agreed, as long as the series resistor remains within reasonable limits, 
like your 470K example.  SNR of the preamp diminishes with the an increase 
in series R from the crystal element.  I measured this effect a while back 
when trying to optimize the series R level into the gate of an FET.  Above 
about 500K, it becomes worthwhile to investigate a low-noise FET to unload 
the crystal element.  The higher the series R value, the more important the 
choice in the noise figure of the first AF stage transistor.  For FETs, I 
like the LSK170.  For BJTs, the Toshiba BC550 and BC560 are excellent where 
input loading Z is not much of a concern.


For SSB transmitters using crystal filtering (e.g., 2.4K I.F. filter) , I 
cannot imagine the need to go above 500K of series R from the D104 element. 
There's no way the resulting response through a traditional filter is going 
to increase  -- like it does for AM transmission or ESSB-capable 
transmitters.  One can often move the carrier set point to a different point 
on the crystal filter curve but that comes at the expense of either the 
upper or lower audio response, depending on the set point shift.  And, that 
can introduce frequency reading errors in transceivers that have no means to 
compensate.


The stock Astatic 2-stage preamp is an engineering disaster IMO.  It uses a 
strange variation of collector feedback bias and has far too much gain 
available to the operator.  For the number of parts involved, it offers poor 
noise, gain, and response performance.  It could definitely benefit from 
negative feedback that's consistent across the usable audio range.  By the 
way, the input Z of Astatic's 2-stage preamp computes to roughly 450K.  So, 
it's reasonably unloading the element for SSB users.  But sonically, it's 
not up to the task.


Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] D104 and TR7

[Paul Christensen]

Woody,

You can add a 100K resistor in the D104's + mic lead.  That will help to unload 
the crystal element from the TR-7's moderately low input Z.  Same is true if 
your D104 uses Astatic's 2-transistor preamp/buffer circuit.  The input Z of 
Astatic's preamp is still too low to take full advantage of an unloaded crystal 
mic element.  On the other hand, the TR-7's SSB transmit filter will strip away 
much of the "full-bodied" audio from the D104.  So, apart from adding the 100k 
resistor, I wouldn't change anything else.  If you were going to use the D104 
with a modern DSP-based transceiver, I would have suggested gutting the Astatic 
preamp and replace it with one of the FET buffer circuits shown on my QRZ.com 
page.

Paul, W9AC
  
  - Original Message - 
  From: Woody 
  To: Drake List 
  Sent: Wednesday, July 06, 2011 9:19 PM
  Subject: [Drakelist] D104 and TR7


  Does any one know the mod to make the 104 work well with the TR7, I was told 
you added a resistor of some value but they didn't know the value or where to 
put it. I need to know it at the Mod's for Dummies level, I was a Toolmaker not 
a electronics man, well just enough to be dangerous and stay alive. 

  Thanks 
  Woody
  -- 





--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Drake R-4C Power Transformer Orientation

[Paul Christensen]

Rob Sherwood just sent me the data below, confirming my finding that AC flux 
induction is worse on the R-4C PTO when the VFO is run up top where the 
ferrite core extends furthest to the rear of the receiver.  Notice the 13 dB 
difference in modulated PTO 60 Hz sidebands between VFO extremes.


Rob will send me his "before and after" transformer rotation spectrum 
measurements.  I'll post here when completed.


Paul, W9AC

"I measured the ripple on the PTO at three frequencies on an R-4C in here 
for service using my HP 3585A spectrum analyzer.   The value is for the 
line related sidebands on two of the frequencies, and sidebands at 120, 
180, 240 Hz on the highest frequency.  The line-related sidebands go out 
further than 240 Hz, and are down about 80 dB at 480 Hz


Receiver freq.60 Hz  120 Hz 180 Hz 240 Hz
Tuned 14.0 MHZ  -46 dB
Tuned 14.2 MHZ  -39 dB
Tuned 14.5 MHZ  -33 dB, -48 dB, -57 dB, -63 dB

Of course the band one is on makes no difference, as the hum sidebands are 
magnetically coupled into the PTO.


I will have my tech turn around a transformer on one of my C-Lines in the 
coming weeks.


73, Rob, NC0B



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Power Transformer Rotation

[Paul Christensen]

As promised, here's my update concerning the R-4C power transformer and PTO 
modulation.  First a special thanks to Bill, W6FF for providing me with a 
NOS R-4C transformer.  Very much appreciated.  However, a rare occurrence of 
good fortune came to me.  It turns out that the existing R-4C transformer 
can be rotated 90 degrees and still have enough lead length on the 
transformer wiring to terminate the end points -- at least on my R-4C. 
Since transformer installation and wire termination was a manual process at 
Drake, exact lead lengths will differ.  That said, I had more than enough 
wire length to accomplish the task without having to try the NOS 
transformer.  In the links to images below, you can see the transformer 
after rotation as well as a ground lug added the PTO shield.  The addition 
of the lug was suggested by Rob Sherwood in his PowerPoint presentation.  He 
reasoned that the spade mounting forks do not always make good metal contact 
with the PTO frame to adequately allow for good PTO shielding -- although 
aluminum is a relatively ineffective shield against low frequency flux.  In 
his case, he was able to attain a 10 dB reduction in flux induction with the 
addition of the ground lug.


http://72.52.250.47/images/R4C.jpg

http://72.52.250.47/images/R4C-1.jpg

The rotation worked.  At no point of VFO rotation can I detect PTO carrier 
modulation.  This is not to say that it is 100% eliminated.  A spectrum 
analyzer is needed to ensure absolute PTO oscillator purity.  However, any 
remaining level of induced flux has now dropped down to the point of being 
inaudible.  I'm saving my pennies for an HP 8591E spectrum analyzer w/ 
tracking generator.  Every time I save enough, temptation comes over me like 
it did last Thursday when I purchased a mint S/Line.  When I do obtain the 
SA, I plan on making more tests, including effects with Mu-metal shielding. 
I'm still looking for a source of authentic Mu-metal sheeting.


I was also concerned about potential mechanical interference to the crystal 
calibrator board with the transformer rotated.  Good news again.  There's 
still ample room to insert/extract the calibrator board to/from its socket. 
No issues here.


Transformer re-mounting:  Even more good news.  Unlike the R-4B transformer, 
the R-4C transformer mounting centers form a perfect square and the existing 
chassis holes are fine for mounting after rotation.  However, new chassis 
access holes ARE required for the transformer wiring.  I used a Greenlee 
3/4" chassis punch to form two new holes.  The chassis is still plenty 
strong after inclusion of the new holes, especially since the transformer 
mounting frame helps to ensure that the chassis remains rigid after bolt 
tightening.


For anyone contemplating transformer rotation, it's a good idea to first 
pave the way for a chassis punch.  I temporarily removed the chassis fuse 
holder and AC line select switch.  This gave me all the room I needed 
without causing damage (and I'm good at causing damage to my gear in the 
shop).  Before removal of these two items, I drew a sketch to help remind me 
of wiring placement.  A quick snapshot with a digital camera is also a good 
idea.


Paul, W9AC






___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C PTO Hum

[Paul Christensen]

Garey,

Thanks for the tip.  I did check with John, but no luck.  However, I may 
have found an alternative.  Newark has Plastic Snap Rivets that may work.


http://www.newark.com/jsp/content/printCatalog.jsp?cat=catalog128&page=2137&display=single

I'll order a pack and try them.  Seems like missing chassis bumpers are a 
common problem after the receivers are repeatedly turned upside down for 
shop work.


Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Cabinet Bumpers

[Paul Christensen]

With all the R-4C work going on here, I have managed to loose (or break and 
then loose) the two small top cabinet bumpers located at the top rear of the 
R-4C.  These are black in color, flat, and are press-fit into the back top 
lip of the chassis.  Anyone have a pair to sell or is the OEM still selling 
them through a distributor?  Tnx!


Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4A PTO, Round 1

[Paul Christensen]

Steve,

No doubt others with more experience will jump in.  I've recently pulled more 
than a half-dozen PTOs in the last week.  The first one takes a bit of time to 
think through but the info on WB4HFN's website is excellent.  After the first 
trial, subsequent removal of the whole assembly with dials can be performed in 
about 5 minutes.  I found that with the PTO sitting on a bench, and 
interconnected with RG-174, I could much more accurately analyze problems and 
performs maintenance on the units.  Removal of the entire PTO is a "must" if 
you want to inspect the bottom of the PTO's circuit board.  I have an angled 
dental mirror but it's no substitute for PTO removal.

Anyway, once the PTO is out, you should be able to confidently and easily 
determine whether the problem is electrical or mechanical.  The Zener helps to 
stabilize line voltage variations.  If the PTO is "jumping," I would think it 
may be a mechanical problem -- or perhaps the issue where the PTO "braid fix" 
will help.   Either way, I would try to pull the PTO and at the same time, 
perform maintenance on the bearings, clean the dials, etc as long as it's open 
and accessible.

Paul, W9AC


- Original Message - 
  From: Steve Wedge 
  To: drakelist@zerobeat.net 
  Sent: Monday, July 04, 2011 3:33 PM
  Subject: [Drakelist] R-4A PTO, Round 1


  I finally pulled my R-4A out of its place on my operating desk and got the 
covers off.  As I was undoing the nuts in preparation for PTO removal, I 
noticed that there was a 10V zener on the small board that the wires from the 
PTO connect.  I also noticed that one end was broken but still touching its 
connection.

  A couple of things come to mind.  First, the schematic and comments I've 
heard from others on this list strongly suggest that the zener should be inside 
the enclosure.  Second, if that's true, then a previous owner tried to correct 
my "frequency-jumping" problem by installing the zener externally to the 
enclosure to avoid the extra work.  Could it be possible that the zener inside 
the enclosure is still behaving erratically and intermittently conducting at 
some voltage below that of the external zener?  I haven't pulled the receiver 
back off the desk (arh...) yet and wanted to get a general opinion.

  Am I right in assuming that this zener - which was installed on the back-side 
of the little board - was added on?

  Steve Wedge, W1ES/4

  "I can't complain, but sometimes I still do."
  - Joe Walsh

  If the above message appears, it came from Steve's Son of Laptop!


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C PTO Hum

[Paul Christensen]

Garey,

I've been messing around with various metal sheets but I really need to get 
a better bond on the chassis.  Taking another look at the AC transformer 
wiring, it appears that if the transformer is rotated in the right 
direction, the lead lengths will all work fine and won't need extending. 
However, it will require the drilling of additional chassis holes and I'll 
need to dig out my OM's old set of Greenlee chassis punches which love 
aluminum but hate steel!  Also, the crystal calibrator must be re-located. 
I've been using tapped right-angle aluminum brackets for my SM0VPO audio 
boards and these will work nicely with the calibrator since the cal board 
already has mounting holes that are presently used with Nylon stand-offs. 
The calibrator will then be mounted on one end.and also out of the way of 
the transformer flux field just to be on the safe side.  By changing the 
mounting orientation, I also do not want to move the flux problem elsewhere. 
In looking at the layout, I see nothing that should be of concern -- but I 
won't know 'till it's tried.


I plan on ordering Mu-metal sheeting in the event additional PTO shielding 
is needed, but I'm confident that just rotating the transformer will lick 
the problem.  The current orientation between PTO and the R-4Cs power 
transformer could not have been worse.  Moving the PTO laterally just one 
inch in either direction substantially reduces PTO modulation by the 
transformer flux.  But, the PTO has to remain where it us due to all the 
dial mechanics.


Paul, W9AC




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] NOS R-4C Transformer Wanted

[Paul Christensen]

A few months back, several folks indicated they has NOS R-4C transformers 
and of course, I didn't save all the replies once I obtained one.   S, 
if anyone has a NOS R-4C transformer with full length leads, please reply 
direct.  Many Tnx!


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C PTO Hum

[Paul Christensen]

Stayed up last night and tried Garey's excellent suggestion.  I could hear a 
difference, but not enough to claim victory over the problem.  Rob Sherwood 
wrote back and his notes confirm my findings.  In fact, he addressed this 
issue in a PowerPoint presentation he gave at last year's Dayton Hamvestion. 
Rob sent me a copy of the presentation by E-mail attachment.  I don't see it 
on his website but he had documented the magnetic flux problem with a 
spectrum analyzer.  Just to be clear. this isn't 60 Hz ground loop hum. 
Rather, the 60 Hz transformer flux is modulating the PTO, creating many 
sidebands above and below the PTO carrier frequency.  When he placed the PTO 
on the bench, the PTO carrier is clean to about -100 dBc and completely 
absent of any 60 Hz sidebands.  With the PTO placed in the R-4C, the first 
60 Hz sideband is down only -26 dBc.  I don't know if he made the latter 
measurements at the 500 kHz VFO markings.  However, he indicated that the 
locking spade pins on the PTO shield make intermittent contact to the 
mounting frame and by adding a ground lug to the PTO shield, he achieved a 
10 dB reduction in sidebands -- but this is hardly enough.


I strongly suspect the significance of power transformer orientation had 
become lost by Drake engineers in the years after early R4 development.  The 
R-4B's transformer is oriented properly so there's no flux induction. 
There's a significant difference in PTO modulation based on the orientation 
of the PTO to the transformer.  Flux induction to the PTO is highest when 
it's in-line with the grain of the transformer laminates (as it is in the 
stock R-4C).  But perpendicular (like the R-4B), the problem disappears to 
the point that I can even push the PTO right up to the transformer case will 
no ill effects, although a spectrum analyzer would likely show more detail. 
Rob's spectrum analyzer photos reminded me again why I need an SA here for 
this kind of investigative work.  There's only so much one can do to isolate 
problems in the time domain.


Paul, W9AC




- Original Message - 
From: "Garey Barrell" 

To: "Paul Christensen" 
Cc: "Drakelist group" 
Sent: Thursday, June 30, 2011 9:53 PM
Subject: Re: [Drakelist] R-4C PTO Hum



Paul -

Interesting.

Something to try.  A piece of copper wire, as big as will fit, looped 
around the outside of the transformer in the same plane as the transformer 
winding.  Short the ends together, forming a complete 'shorted turn' 
around the transformer.


I suspect a sheet of mu-metal stuck vertically behind the PTO, (don't 
forget the extension of the guide pin!,) might also help.


Hopefully a combination of small 'fixes' can take care of the problem, 
rather than go through the pain of re-orienting the power transformer!


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:
I spent a part of the afternoon isolating the PTO audio fuzziness I 
described when the VFO dial is moved from "0" then upwards to "500" when 
listening to a CW carrier.  I hear a pure, clean CW carrier at the "0" 
VFO position but then progressively gets worse, ending at "500."  Based 
on how the fuzziness behaved, I guessed that it was more than likely 
related to a magnetic field -- either the power transformer or filament 
AC currents in the chassis.  So, I completely disassembled the entire PTO 
and dial assembly and placed it on the bench, about a foot away from the 
R-4C.  I ran RG-174 from the PTO to the R-4C.


Sure enough, the problem is completely gone when the PTO is external to 
the receiver.  After about an hour of testing, here's what going on:


As the dial changes from 0 to 500, the PTO's ferrite core moves toward 
the back of the receiver.   As the core moves rearward, it is also coming 
nearer to the AC power transformer.  PTO cores are especially susceptible 
to magnetic fields.  To prove to myself the AC power transformer is the 
culprit, I took the PTO assembly in my hands and moved to and from the 
transformer.  When the PTO is within about three inches of the 
transformer, the CW note starts to become fuzzy.  The degree of magnetic 
coupling is highly dependent on the orientation of the PTO to the flux 
field of the power transformer.  The current orientation of the PTO with 
the transformer core (i.e., PTO core in-line with the laminate core 
direction, produces the worst results.  By contrast, there's no fuziness 
whatsoever if I take the PTO and run it right up to the transformer when 
the PTO core is 90 degrees perpendicular to the orientation of the 
transformer core.


If a were a "bettin" man, I would say a great number of R-4Cs (but NOT 
R-4Bs - see below) are affected by this -- some to a greater degree than 
others.  I noticed this 

[Drakelist] R-4C PTO Hum

[Paul Christensen]

I spent a part of the afternoon isolating the PTO audio fuzziness I 
described when the VFO dial is moved from "0" then upwards to "500" when 
listening to a CW carrier.  I hear a pure, clean CW carrier at the "0" VFO 
position but then progressively gets worse, ending at "500."  Based on how 
the fuzziness behaved, I guessed that it was more than likely related to a 
magnetic field -- either the power transformer or filament AC currents in 
the chassis.  So, I completely disassembled the entire PTO and dial assembly 
and placed it on the bench, about a foot away from the R-4C.  I ran RG-174 
from the PTO to the R-4C.


Sure enough, the problem is completely gone when the PTO is external to the 
receiver.  After about an hour of testing, here's what going on:


As the dial changes from 0 to 500, the PTO's ferrite core moves toward the 
back of the receiver.   As the core moves rearward, it is also coming nearer 
to the AC power transformer.  PTO cores are especially susceptible to 
magnetic fields.  To prove to myself the AC power transformer is the 
culprit, I took the PTO assembly in my hands and moved to and from the 
transformer.  When the PTO is within about three inches of the transformer, 
the CW note starts to become fuzzy.  The degree of magnetic coupling is 
highly dependent on the orientation of the PTO to the flux field of the 
power transformer.  The current orientation of the PTO with the transformer 
core (i.e., PTO core in-line with the laminate core direction, produces the 
worst results.  By contrast, there's no fuziness whatsoever if I take the 
PTO and run it right up to the transformer when the PTO core is 90 degrees 
perpendicular to the orientation of the transformer core.


If a were a "bettin" man, I would say a great number of R-4Cs (but NOT 
R-4Bs - see below) are affected by this -- some to a greater degree than 
others.  I noticed this mainly because I've upgraded the entire path from 
the product detector to the final AF amp.  Audio fuzziness on both CW and 
SSB that were previously masked by mediocre audio performance are now 
clearly audible -- but only when the PTO is on the top of the band -- like 
when I'm listening to 75m around 3950 kHz.  Down on the CW band edges, all 
if fine.


Some ideas on where to go from here and I would like input from others:

1) Investigate a real Mu-metal shield for a PTO cover.  The stock PTO shield 
is aluminum and is fine for RF shielding -- but wholly useless for low 
frequency magnetic fields.  This is where Mu-metal shines.  Mu-metal is 
composed of 75% nickel, 15% iron, 15% copper and/or molybdenum;


2) Turn the power transformer 90 degrees.  Easier said than done because 
there are no service loops in the transformer wiring.  Would take extending 
the leads -- or purchasing a NOS transformer, subject to availability.  I'm 
also unsure if the Xtal Cal board interferes with the transformer in that 
orientation.  More measurements needed;


3) Bolt the AC power transformer to the back of the R-4C and get the flux 
field out of harm's way.


Here's the kicker.  When I replaced the power transformer in my R-4B with an 
R-4C transformer to gain some advantages previously discussed here, I 
oriented the transformer 90 degrees from the R-4C mounting scheme as the 
R-4B's transformer is 90 degrees turned from the R-4C orientation.  I'll bet 
R-4B PTOs are probably cleaner than that of the stock R-4C when the VFOs are 
tuned up to "500."   My R-4B with all the audio mods and new R-4C 
transformer does not exhibit this problem.


I'm glad I conclusively found the root cause but I'm a bit bummed-out over 
what this next level of refinement is going to take to fix.  There, I said 
it.  This is a fix to a design problem.   Sure, the R4 receivers are meant 
for communications and not audiophile use -- but the problem could have been 
managed better in design.  It seems more proximity testing of  PTOs to the 
magnetic field of the power transformer was in order.  Or, perhaps Drake did 
run these tests with the older A and B series but became complacent when 
they changed the transformer orientation in the C series.  Pointless to 
guess, I suppose.


Paul, W9AC




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Lexan Dials

[Paul Christensen]

Thanks to all for your replies...

Turns out I've got a larger issue to resolve.  I am hearing 60 Hz hum on all 
signals, including the Xtal Cal. and off-air signals but only as the PTO is 
run up about half way and gets slowly worse as its moved up to the top at 
500 kHz.  Looked at it on a scope and the first beats occur right at 60 Hz 
as confirmed with a frequency counter.  Definitely not a 120 Hz ripple 
issue.   So, its likely a PTO grounding problem but the braid trick as shown 
on various websites has no effect.  It's almost like there's a ground loop 
but what's odd is that the 60 Hz hum gradually changes across the PTO span.


Unfortunately, this is one of those difficult problems that's going to 
require a lot of patience and trials to isolate.


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Paul Christensen" 
Sent: Wednesday, June 29, 2011 4:38 PM
Subject: Re: [Drakelist] R-4C Lexan Dials



Paul -

Yes, they DO warp.  It seems the most common problem is that they rub on 
the back of the front panel.  If the interference is 'out of sight', some 
have put a small piece of felt below the dial window.  If they are rubbing 
together, it's a little more difficult, but again a piece of felt in an 
out of sight location can prevent rubbing.


I have investigated making after-market dials, but there are five or six 
different ones, and very big minimum orders.  I don't have sufficient cash 
lying around to cover the experiment!  :-)


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:
At several points of VFO rotation, my R-4C Lexan dials come together and 
make a slight noise.  This is due to the dials having become warped over 
the years.  I checked two T-4XC and they too have warped dials although 
they do not yet come in contact.  the noise is definitely from dial 
warpage and not a mechanical alignment issue.


I went so far as to swap PTOs with my spare T-4XC but for an unknown 
reason, the PTO would exhibit hum on the Xtal Cal. carrier when tuned up 
toward 500 kHz.  The hum lessened as it was tuned back down in the other 
direction, completely disappearing at 0 kHz.  I looked at lead dressing 
and gave up so I put the old PTO back in.  Seems that PTOs in T-4XCs have 
considerably less wear on them since they are not spun as much so it 
would have been nice if that worked.


Anyway, has anyone found a fix for this?  I imagine NOS Drake dials are 
rare to find.  Tnx!


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Lexan Dials

[Paul Christensen]

At several points of VFO rotation, my R-4C Lexan dials come together and 
make a slight noise.  This is due to the dials having become warped over the 
years.  I checked two T-4XC and they too have warped dials although they do 
not yet come in contact.  the noise is definitely from dial warpage and not 
a mechanical alignment issue.


I went so far as to swap PTOs with my spare T-4XC but for an unknown reason, 
the PTO would exhibit hum on the Xtal Cal. carrier when tuned up toward 500 
kHz.  The hum lessened as it was tuned back down in the other direction, 
completely disappearing at 0 kHz.  I looked at lead dressing and gave up so 
I put the old PTO back in.  Seems that PTOs in T-4XCs have considerably less 
wear on them since they are not spun as much so it would have been nice if 
that worked.


Anyway, has anyone found a fix for this?  I imagine NOS Drake dials are rare 
to find.  Tnx!


Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R4A KNOB INLAYS

[Paul Christensen]

Check with Alan, KC9YS.  He recently supplied me with a new VFO knob set for a 
B line.  He may also be able to provide just  the inlays.

Paul, W9AC
  - Original Message - 
  From: FRANK MILLER 
  To: Drakelist@zerobeat.net 
  Sent: Saturday, June 25, 2011 9:21 PM
  Subject: [Drakelist] R4A KNOB INLAYS


  Does anyone know for sure if there is a source for the knob inlay that has 
the small skirt
  or rim around the edge as apposed to being flat? The sources on the DRAKE 
lists do not
  respond to my inquiry.
  Frank WA0ILV


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4B Notch Backlash & PTO movement

[Paul Christensen]

Garey,

Tnx for the great suggestions!

Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: 
Sent: Sunday, June 19, 2011 4:57 PM
Subject: Re: [Drakelist] R-4B Notch Backlash & PTO movement



Paul -

Yes, the adjuster for the NOTCH is 'springy' like the Passband Tuner 
slugs.  The backlash is usually negligible if the cam slider surface is 
clean and lightly lubricated.


Seems a little strange.  Any 'play' in the front ball bearings is adjusted 
out with the hex set screw accessible from the back end, just like the C.


Since it's only 'UP', I wonder if all three of the spade bolt nuts that 
hold the PTO in the receiver are  tight??


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:

Just noticed two very slight anomalies with my R-4B:

1) There's a small bit of Notch control backlash; and

2) There's a very small amount of VFO knob upward movement but no 
side-to-side, nor downward movement.  The slight upward movement does not 
affect frequency stability.


Is this normal for the R-4B?  I detect neither issue with my R-4C.  Tnx!

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4B Notch Backlash & PTO movement

[Paul Christensen]

Just noticed two very slight anomalies with my R-4B:

1) There's a small bit of Notch control backlash; and

2) There's a very small amount of VFO knob upward movement but no 
side-to-side, nor downward movement.  The slight upward movement does not 
affect frequency stability.


Is this normal for the R-4B?  I detect neither issue with my R-4C.  Tnx!

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Ten-Tec and Drake Compared

[Paul Christensen]

Ten-Tec definitely catered to the QSK CW crowd. I know that the Drake
4-line could be made to work QSK with an external T/R switch. Has anyone
on list done this and can comment on the QSK performance? Escpecially
how it compares to Ten-Tec's QSK.


Darrell:

I'm using my C Line in QSK mode with the help of: (1) Ameritron QSK-5 PIN 
diode T/R switch; and (2) a PIC-based CW keyer.  The keyer is the device 
that establishes complete system timing.  New keyers have the ability to 
adjust the lead-in and tail times between the Keyed output and PTT line. 
So, it's now possible to use classic separates in super-fast QSK mode.  By 
fast I mean near full-duplex.  The supreme irony is that with this set-up 
it's possible to attain significantly faster and seamless  QSK with say...a 
Heathkit DX-60 and Drake R-4B than a Ten Tec Orion II.


The system works around the existing C Line T/R system and requires no 
equipment modification.  Well, as an option one could bring out another 
buffered PTT output from the QSK-5 to bias the T-4Xx transmitter when in SSB 
mode.  Or, just let Ip idle all the time.


An even better system is being developed between myself and a keyer 
manufacturer.  It will allow for independent lead-in and tail times such 
that one can look at the keyed CW RF envelope on a scope and customize 
timing to active the PIN diode switch moment exactly 1 msec before transmit 
RF and 1 msec after the trailing tail of the CW envelope -- and that's 
extremely important with Drake gear since the CW envelope rise in only about 
2 msec, but has the classic grid-block keying characteristics of a long R/C 
non-linear discharge as it asymptotically reaches zero.


This system only works for "separates."   For the past thirty years, 
manufacturers have had to compromise on QSK performance in order to contend 
with PLL and synthesizer settling times.  Transceivers generally use the 
same oscillator for Tx and RX but the oscillator does not settle fast enough 
between T and R to allow for super-fast QSK.  That's why you see T/R 
turnaround times in QST Product Reviews in the range of  10-30 msec, the 
longest of which is the Flex-Radio gear.  With the Flex, there's just too 
much latency to achieve any semblance of QSK.  Direct RF sampling shows the 
best promise for future QSK performance from SDR transceivers as hardware 
handles the lion's share of processing horsepower and not a Microsoft 
Windows software application (e.g., PowerSDR).


The beauty of this system is that the PIN diode switch allows just enough Tx 
to Rx leakage for one to get about a 10 dB over S9 signal on the receiver 
while transmitting in CW.  So, you're listing to your own signal in real 
time and switching is so fast that your own signal is heard as just another 
signal on the band.  The Tx and Rx VFOs are free-running and do not have the 
handicap of needing to switch by the amount of the CW offset between T/R 
excursions.


Paul, W9AC






___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Collins, Drake etc.

[Paul Christensen]

So, truth be told, while Collins gear was clearly the high priced spread, 
even Drakes were still out of reach for us average joes who made do with 
Heathkits...


Toward the end of its life, the R-4B + T-4XB was right at $1K.  I can't 
imagine spending that during my teenage years in the mid 1970s.  To me, it 
was like a car purchase.  By 1975, what was the street price of the S-Line 
combo?  I imagine Collins offered little in the way of discounts.  I make 
this assumption based on the back pages of QSTs I've been reading from the 
late '50s.  For example, every single dealer who supplied the KWM-1 
advertised it for exactly $820 in 1958.  It sure seems like Collins had 
strict terms and conditions on just how much a dealer could discount, if any 
at all -- much the same way other high-end products are sold today in order 
to retain an elite branding image.  I imagine this was less of an issue with 
Drake.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] SM0VPO Audio Board in R-4C

[Paul Christensen]

"Would you mind giving more details about how the antivox output is connected 
in your R-4B audio mod?  I might do something similar to an R-4A.

Thanks,
Kihwal, K9SUL"

Kihwal,

I have Antivox connected to the normally-closed contact on the headphone jack.  
My headphone jacks are all converted to two-circuit Switchcraft Tip/Ring/Sleeve 
types so that any stereo headset can be used without hunting for an adapter.  

My Antivox works only when listening to a speaker and keeps any induced noise 
and RF off the headphone jack when the headphone plug is inserted.

Paul, W9AC___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] SM0VPO Audio Board in R-4C

[Paul Christensen]

The SM0VPO audio board worked so well in the R-4B, I decided to add one to 
my R-4C -- which is a much easier exercise when the Sherwood PS-4 board is 
already installed.  The photos in the links below were taken last night 
after I completed installation.  Well, it was finished last week, but it 
took several grounding iterations to get it right with no trace of buzz due 
to circulating filament currents.  Like my recent R-4B installation, there 
is absolutely no hiss, hum, or buzz at any AF control setting.   The output 
transistors run cold to the touch and only get slightly warm when 
continuously running at high power levels into the MS-4 speaker.


Getting near audiophile grade performance from a circuit that's designed to 
work into *both* headphones and a speaker from a single-ended supply is no 
easy accomplishment.  I'm still amazed at the design.  The photos below show 
the one and only manner of installation (that I can figure out!) into the 
R-4C.  The board is mounted sideways on angled aluminum brackets such that 
the NB-4 can still be plugged into the top without creating any mounting 
interference.  The location is good since it is away from the magnetic flux 
field of the power transformer and AC HV line.  Although not easily seen, a 
Zobel network was installed, consisting of the usual 0.1 uF cap in series 
with a 10-ohm resistor at the AF output.  The large black cap is  
2,700 uF on the AF output line.  Ultra-low noise Toshiba BC550/BC560 
transistors used in the high-gain stage, with ample power supply de-coupling 
between the high gain stage and the high-current TIP41 transistor drivers.


http://72.52.250.47/images/R4C-1.jpg
http://72.52.250.47/images/R4C-2.jpg
http://72.52.250.47/images/R4C-3.jpg

Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Collins and Drake Compared

[Paul Christensen]

Great set of responses, both from public and private E-mails.  Many thanks 
to all for your input. It was a real learning experience for me since I have 
not "lived the moment" with a Collins S Line.


Paul, W9AC


 Original Message - 
From: "Paul" 

To: 
Sent: Wednesday, June 15, 2011 10:52 PM
Subject: Re: [Drakelist] Collins and Drake Compared



My 2cents worth

I've had the pleasure of owning both B and C lines,as well as a Collins S3 
line. I liked the Collins S line,it was well designed & built,and sure 
performed well,but it's gone 3 years and I still have my B and C lines.

Main reason was lack of 160 meters on S line,but not the only reason.
I could hear anything on my Drakes as well as I could on my Collins. 
Drakes took up less real estate on the desk also. The two were about the 
same for vfo drift,not bad,but VERY respectable.

Big plus is the pretty blue meters / dials!
Nuff said

AD3G

On 6/14/2011 10:30 PM, Paul Christensen wrote:
For the past few weeks, I've been comparing receive structures between 
the Drake 4 series and Collins 75S-3 series.  I'm surprised by the 
similarities - as well as the differences.


Some obvious differences:

- Mechanical IF filter versus crystal or LC filtering;
-160m coverage ability;
- Tunable BFO versus PBT;
- Q Mult in 75S-3.

Similarities:

- PTO VFO with 1 kHz dial markings;
- Preselector (similar octave structure?);
- Crystal 1st LO (unlike early JA receivers during the same time period);
- Audio power and AF driver stages similar to R-4B;
- Extensive use of RCA jacks, including RF IN;

Collins, like Drake, used PBT in the 1950s and I'm curious why it was 
abandoned in the S line.  Perhaps too complex to use among 
commercial/military/amateur users?  In essence, the least common 
operating denominator wins?


Both series use the chassis for the filament return, although Collins 
used four (!) heater lines in the 75S3.   I found Collins' treatment of 
the headphone jack quite interesting.  They use a resistive divider 
network to load the output line during periods of high Z loads.  Seems 
wholly unnecessary given that the 4-ohm transformer tap is routed through 
the H/P jack's N/C contacts and the 500-ohm tap makes use of the divider 
in which one resistor is bypassed during insertion of headphones.


My recollection of the S line tuning feel is sketchy but I recall a 
superbly designed VFO tuning mechanism onto the PTO -- probably at least 
as mechanically well designed as the those found in the Drake 4 series?


Perhaps the Collins S line has a slight edge with quality of construction 
and components although I've not taken a look at whether the 75S-3 uses 
ceramic switch wafers versus Phenolic -- and whether they used Teflon 
harness wiring (where Drake fails).I have nearly no operating time 
with an S line and I was considering a purchase.  But based on what I'm 
seeing in the schematics, I'm not impressed enough to unload my bank 
account for a S line.  This may seem  like a "trolling" exercise to some, 
but I find the comparison between the two products to be very interesting 
especially when comparing cost and evolution of their product lines.


Thoughts on the matter very much appreciated.

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Collins and Drake Compared

[Paul Christensen]

For the past few weeks, I've been comparing receive structures between the 
Drake 4 series and Collins 75S-3 series.  I'm surprised by the 
similarities - as well as the differences.


Some obvious differences:

- Mechanical IF filter versus crystal or LC filtering;
-160m coverage ability;
- Tunable BFO versus PBT;
- Q Mult in 75S-3.

Similarities:

- PTO VFO with 1 kHz dial markings;
- Preselector (similar octave structure?);
- Crystal 1st LO (unlike early JA receivers during the same time period);
- Audio power and AF driver stages similar to R-4B;
- Extensive use of RCA jacks, including RF IN;

Collins, like Drake, used PBT in the 1950s and I'm curious why it was 
abandoned in the S line.  Perhaps too complex to use among 
commercial/military/amateur users?  In essence, the least common operating 
denominator wins?


Both series use the chassis for the filament return, although Collins used 
four (!) heater lines in the 75S3.   I found Collins' treatment of the 
headphone jack quite interesting.  They use a resistive divider network to 
load the output line during periods of high Z loads.  Seems wholly 
unnecessary given that the 4-ohm transformer tap is routed through the H/P 
jack's N/C contacts and the 500-ohm tap makes use of the divider in which 
one resistor is bypassed during insertion of headphones.


My recollection of the S line tuning feel is sketchy but I recall a superbly 
designed VFO tuning mechanism onto the PTO -- probably at least as 
mechanically well designed as the those found in the Drake 4 series?


Perhaps the Collins S line has a slight edge with quality of construction 
and components although I've not taken a look at whether the 75S-3 uses 
ceramic switch wafers versus Phenolic -- and whether they used Teflon 
harness wiring (where Drake fails).I have nearly no operating time with 
an S line and I was considering a purchase.  But based on what I'm seeing in 
the schematics, I'm not impressed enough to unload my bank account for a S 
line.  This may seem  like a "trolling" exercise to some, but I find the 
comparison between the two products to be very interesting especially when 
comparing cost and evolution of their product lines.


Thoughts on the matter very much appreciated.

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] value of early drake gear

[Paul Christensen]

"...worth next to nothing, when compared to the rest of the 4 line. I have 
owned a B-line,a C-line in the past ,both good performers,B being my 
choice between the two. I find the early 4 line performance ,from my ear 
and operation just as good as my B-line. Of course I never had the chance 
to run them side by side..."


For the past month, I've been running my R-4B and Sherwood R-4C 
side-by-side.  The R-4B has been a more enjoyable receiver to use, although 
the "modded" R-4C is incredibly good in tight band spaces among strong 
signals.  High S/N R-4Cs seem to command the highest prices in the 4 line, 
but if one wants to later change the R-4C with all the Sherwood mods, I'm 
not sure why a high S/N matters.  The only real consideration in my 
selection among S/Ns had to do with getting one with metal/Nylon mesh gears 
only because to me, that combination produces the most solid tuning feel 
among the dozen or so R-4Cs I've owned in the last twenty years.  My R-4C is 
around S/N 26,950.


When I received my R-4B earlier this year, it was my first.  I absolutely 
hated it.  But the root cause for that hate was in the power supply 
filtering.  Enough ripple had caused CW and SSB transmissions to sound 
"fuzzy," resulting in a high amount of audio IMD.  The fuzz went away when 
the main supply cap was changed and that lead to my OCD taking over and 
making many other changes to the R-4B that are documented in the list 
archives.


The R-4B is capable of truly Hi-Fi audio.  Unfortunately, the R-4C's 
greatest strength is also one of its greatest weaknesses.  For example, 
low-frequency (below ~ 300 Hz) and upper SSB frequency audio response is 
forever compromised owing to the use of cascaded crystal filters.  In recent 
years with DSP transmit IF schemes, enough SSB stations have now expanded 
the TX SSB audio passband to 100Hz - 3000 Hz where the difference in 
perceived audio balance can be remarkable in instances when the received 
signal strength is strong.  This distinction can be easily heard with the B, 
but not the C.   In a nutshell, my R-4C will be used for tough band 
conditions and the R-4B used for ragchews on both SSB and CW.


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake R-4C Items

[Paul Christensen]

Drake items now gone to new homes.   Thanks to all for reading...

Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Drake R-4C Items

[Paul Christensen]

Most items now gone.  Here's what's remaining:

1) Sherwood Engineering AMP-4 audio amplifier upgrade for R-4C: $30. Last 
one.  Used but perfect condition. Comes with instructions, new bypass caps 
and hook-up wire. Essentially the same as getting the new AMP-4 package 
direct from Sherwood Eng.


2) Drake R-4C 1500 Hz filter, used:  $50

U.S. Shipping $4.95 individually or combined by U.S. Priority Mail Small Box 
Rate.


Many thanks to all!

Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Drake Items

[Paul Christensen]

I have the following items available, shipping extra:

Sherwood AMP-4 audio amplifier upgrade for R-4C:   $30.  Two available, used 
perfect condition.


Sherwood R-4C 600 Hz 1st I.F. Roofing Filter, new never installed:  $90

Sherwood R-4C Two-filter switching with PC board & RF relays with sockets, 
new never installed:  $80


Sherwood R-4C Custom Front-Panel AGC/First I.F. filter switch, new never 
installed:  $70


Drake R-4C 1500 Hz filter, used:  $50

Drake R-4C 500 Hz filter, used:  $50

Drake R-4C 8 kHz Stock Roofing Filter: $25

Will trade either the 1500 Hz or 500 Hz filter for an INRAD R-4C 250 Hz 
filter.


Paul, W9AC







___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Crystals (3rd Mixer LO)

[Paul Christensen]

Gary,

Thanks for the feedback.  The ".999 kHz" spec is so bizarre it seems like it 
was done as an internal joke!


Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "Drakelist group" 
Sent: Wednesday, June 01, 2011 3:47 PM
Subject: Re: [Drakelist] R-4C Crystals (3rd Mixer LO)



Paul -

I don't have a T-4XC open at the moment, so can't measure.  I agree that 
the 1 Hz variation is nonsensical, the crystal is probably spec'd to +/-50 
ppm, or about +/- 300 Hz.  It could conceivably be that they spec'd a 
'little' low to be sure that the actual frequency can be set, but again 1 
Hz isn't enough to matter.


Maybe someone knows for sure?  The earlier transmitters were just spec'd 
as 5.645 MHz, so somebody thought it needed to be changed.!  :-)


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:
The R-4C's 3rd Mixer LO crystal for SSB/CW is 5644.999 kHz.  Why didn't 
Drake just specify 5645.0 kHz?  The tolerance of the crystal is well 
beyond 1 Hz and is likely +/- several hundred Hz.  Perhaps a large 
quantity price break for crystals ground below 5645 kHz?


Any Ideas?

Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Crystals (3rd Mixer LO)

[Paul Christensen]

The R-4C's 3rd Mixer LO crystal for SSB/CW is 5644.999 kHz.  Why didn't 
Drake just specify 5645.0 kHz?  The tolerance of the crystal is well beyond 
1 Hz and is likely +/- several hundred Hz.  Perhaps a large quantity price 
break for crystals ground below 5645 kHz?


Any Ideas?

Paul, W9AC

- Original Message - 
From: "Paul Christensen" 

To: "Drakelist group" 
Sent: Tuesday, May 31, 2011 10:43 AM
Subject: [Drakelist] R-4C Crystals (3rd Mixer LO)


In the process of drilling holes in the chassis of an R-4C to install a 
GUF-1 1st I.F. filter, I managed to let the drill chuck come in contact 
with the 3rd Mixer LO crystals.  I have confirmed that both crystals have 
shattered as a result of the extreme vibration.  S...anyone have a 
crystal pair from a parts unit?  Specifically, they are:


5595.000 kHz
5644.999 kHz.

These are the two crystals mounted on the mode select switch PC board 
(under the mode switch cover).  Many Tnx!


Paul, W9AC




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Crystals (3rd Mixer LO)

[Paul Christensen]

Crystals found.  Many thanks to all!

Paul, W9AC

- Original Message - 
From: "Paul Christensen" 

To: "Drakelist group" 
Sent: Tuesday, May 31, 2011 10:43 AM
Subject: [Drakelist] R-4C Crystals (3rd Mixer LO)


In the process of drilling holes in the chassis of an R-4C to install a 
GUF-1 1st I.F. filter, I managed to let the drill chuck come in contact 
with the 3rd Mixer LO crystals.  I have confirmed that both crystals have 
shattered as a result of the extreme vibration.  S...anyone have a 
crystal pair from a parts unit?  Specifically, they are:


5595.000 kHz
5644.999 kHz.

These are the two crystals mounted on the mode select switch PC board 
(under the mode switch cover).  Many Tnx!


Paul, W9AC




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Crystals (3rd Mixer LO)

[Paul Christensen]

In the process of drilling holes in the chassis of an R-4C to install a 
GUF-1 1st I.F. filter, I managed to let the drill chuck come in contact with 
the 3rd Mixer LO crystals.  I have confirmed that both crystals have 
shattered as a result of the extreme vibration.  S...anyone have a 
crystal pair from a parts unit?  Specifically, they are:


5595.000 kHz
5644.999 kHz.

These are the two crystals mounted on the mode select switch PC board (under 
the mode switch cover).  Many Tnx!


Paul, W9AC




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] SW-4A amp

[Paul Christensen]

A transistorized PP stage can be of significant benefit in a Drake receiver.  I 
was able to reduce the heat and current demands using a simple PP design in a 
R-4B.  The added benefit is extremely low noise, low quiescent current, and low 
distortion without the need for an audio output transformer.   However, one 
significant factor is that a stable, decoupled low-voltage line is necessary to 
power the PP circuit and is likely beyond the ability of most existing Drake LV 
supplies.  But if the Drake LV supply is modified, it can offer tremendous 
increases in operating efficiency and performance over that of the single-stage 
VT design.

Paul, W9AC  
  - Original Message - 
  From: John Boyle 
  To: drakelist@zerobeat.net 
  Sent: Tuesday, April 26, 2011 2:55 PM
  Subject: [Drakelist] SW-4A amp


  The SW-4A amp is not push pull, neither is the amp in the R-4A or R-4B.  
However, the SW-4 does have a push pull amp with two 6AQ5s and 1/2 of a 12AX7 
as a phase inverter.

  Most audio amps consist of two stages.  The first is a voltage amp, usually a 
triode such as one unit of a 12AX7 but sometimes pentodes are used such as the 
6GX6 used in the R-4.  The second audio stage is a power amp, usually either a 
power pentode such as the 6EH5 used in the R-4, R-4A and R-4B, or a beam 
pentode (6AQ5) as used in the SW-4.  There are a wide variety of triodes and 
pentodes used in audio circuits.  There is little point in using a push pull 
audio stage in a communications receiver due to the restricted audio 
frequencies used.  A push pull audio stage requires two more tubes - a triode 
phase inverter and a second output tube - plus additional capacitors and 
resistors so it was not cost effective for most applications. 

  John,  VE3PMA 


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4B Mods (Epilogue)

[Paul Christensen]

Earlier today , I finished the last set of R-4B mods.  Those of you 
following my progress, this marks the ten week point of incremental changes. 
The last (and final, I swear!) set of modifications:


1) Added the Sherwood PD-4 active product detector; and
2) Replaced the Sherwood AMP-4 audio amp with something truly special:  a 
modified form of the SM0VPO Class AB design.  This amp is rated at 4W into 
4-ohms, so it can accommodate both headphones and an MS-4 speaker.  The 
circuit board was made by FAR Circuits, based on the artwork available on 
the SM0VPO website.  IMHO, this is the Holy Grail of "single supply" audio 
amps.


Adding the PD-4 was easy enough now that the Sherwood PS-4 board is 
delivering regulated and decoupled +12V throughout the R-4B.  Findings?  Not 
a whole lot.  AGC attack is much smoother but I notice no other changes.  An 
ancillary benefit of the active design is that In/Out isolation is better 
than that of the diode product detector and as such, there's probably less 
opportunity for audio to feed back into the AGC circuits.


I was not expecting much change between the Sherwood AMP-4 and the discrete 
SM0VPO design.  However, the new amp board elevates the R-4B audio to a new 
level of audio performance.  I searched for low-noise transistors for use in 
the high gain stage and kept the TIP-41 types in the output stage as a truly 
low-Z drive source for the headphones and MS-4 speaker.  The output coupling 
cap is a low ESR type with a whopping 2700 uF of output C.  The only way 
this amp can be improved is to utilize a bipolar supply to attain DC 
coupling between stages.  I cannot justify that level of extra effort just 
for DC-coupling "bragging rights."  Just adding the Sherwood PS-4 to the 
Drake R-4B was complicated enough (see prior message threads for details).


http://72.52.250.47/images/AMP-1.jpg

The discrete audio amp has zero residual noise, no hiss, no hum, no buzz. 
Unlike the monolithic LM3xx series, it's totally silent.  I raised the amp's 
ground buss potential above the R-4B's chassis and used a large conductor 
size between the new amp board's ground buss and a common ground point on 
the Sherwood PS-4.  Likewise, the audio input shield ties back to the same 
ground point.  I did this to avoid buzz-inducing currents on the chassis 
from the AC tube filaments and the CT high-voltage secondary of the power 
transformer.  The common point is in the corner tip of the R-4B chassis -- a 
point where AC currents are minimum.


http://72.52.250.47/images/AMP-2.jpg

I had one issue develop:  As I unplugged the headphones, I noticed 
intermittent instability.  For clues, I went to the National Semiconductor 
datasheets for the familiar LM383, LM380,and LM386 output amps.  Each uses a 
small resistor in series with a cap (e.g., 2.7 ohm in series with 0.1 uF) at 
the output to better stabilize the amp under changing loads (e.g., 
un/plugging headphones).  That worked very well with the discrete design and 
completely cured the instability without affecting performance.


When I have time in the next couple weeks, I will measure the THD and IMD of 
the new amp.  I have a Tektronix TM series test set with 
ultra-low-distortion oscillators and automated distortion analyzer. 
According to SM0VPO, typical THD at 2W is under 0.01%.


So, perhaps now is a good time to summarize all my R-4B mods:

1) Eliminated all power-hungry voltage dividers and substituted with a 
Sherwood PS-4 board;
2) Replaced power transformer with an R-4C NOS unit thanks to the generosity 
of a list member.  This R-4B runs super cool to the touch;
3) Replaced the multi-section power supply cap with a multi-section type 
from Tom at hayseedhamfest.com;
4) Removed the entire R-4B audio section and replaced with a modified SM0VPO 
Class AB audio amp board;
5) Changed H/P jack to TRS so newer stereo phones can be used without 
hunting for an adapter;
6) Replaced all 12.6V tubes to their 6.3V equivalents (e.g., 12AX7 is now 
6AX7).  This, because the R-4C transformer only uses a 6.3V filament 
secondary since the R-4C uses all 6.3V tubes.  From the factory, the R-4B 
has a mix of 12.6V and 6.3V tubes -- and a CT 12V filament secondary;
7) Using an outboard inrush surge limiter on the AC line cord:  Two CL-90 
thermistors in series.  In addition to inrush limiting to the filaments, the 
filaments now see 6.3V instead of 6.8V from my high AC  mains line voltage 
(runs about 125VAC);
8) Replaced all paper caps with "yellow-jacket" metalized Polypropylene 
types;

9) Replaced the diode product detector with the Sherwood PD-4;
10) Replaced both dial lamps with blue LEDs from N9OO.   Love the new look 
against the orange neon dial indicator;
11) Was going to replace a tired NE-2 bulb.  For whatever reason, reversing 
the neon lamp leads has given it new life;

12) Changed AC line cord to 3-wire for safety;
13) Changed AGC "Slow" time constant;
14) Changed several audio coupling and bypass caps to extend the

[Drakelist] R-4B S Meter Drift

[Paul Christensen]

Finally got around to looking at the S meter drift I reported a while back. 
Garey, K4OAH, suggested a gassy V1, V4, or V5.  It was definitely V1, the 
6BZ6.  Tnx Garey!


I was led astray because when I tried several NOS 6BZ6s, the S meter stopped 
drifting but it idled at S7 with S meter "zero" control fully CCW.  Started 
measuring tube voltages, paying attention to the screen and grid.  Screen 
voltages were reasonable, by Pin 1 grid voltages were off by a factor of 2 
with about -3.0 volts.  I then went back to TP2 and realized that changing 
V1 also upset Rx Sensitivity, and that control needed readjusting and wow, 
what a difference.  It took several iterations of adjusting Both S meter 
adjustments and the Rx Sensitivity adjustment to get everything tracking 
correctly and best of all...no more meter drift!


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4B Panel Wanted

[Paul Christensen]

Still looking for a NOS R-4B panel

I have a new set of R-4B audio mods coming that go one step further than the 
Sherwood AMP-4 mod I recently made.  I had FAR Circuits make several 4-watt 
audio amp boards using a modified SM0VPO design.  Ultra low-noise discrete 
transistor design in the gain stage and a pair of TIP41 high-current 
drivers.  Uses a string of 1N914 diodes in a Darlington circuit to minimize 
crossover distortion.  I've been looking a very long time for an 
audiophile-grade amp that runs from a single supply, delivers low 
distortion, low noise, and will work equally well when driving a low-Z 
speaker or headphones.  Nearly all current designs require a +/- bi-polar 
supply to achieve that objective.


Links to photos coming soon.

Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Hayseed Caps

[Paul Christensen]

I just replaced the filter caps in a Drake 1A and R-4B using a Weller 
100/140.  That gun is a hopeless match against the chassis.  Any future 
filter cap changes on copper-plated Drake equiopment will be with big 
wattage soldering iron as many others have suggested..


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4B Modifications

[Paul Christensen]

Last view of the boards shown below...

http://72.52.250.47/images/R4B-5.jpg

Paul, W9AC

  - Original Message - 
  From: Paul Christensen 
  To: drakelist@zerobeat.net 
  Sent: Saturday, March 26, 2011 5:27 PM
  Subject: [Drakelist] R-4B Modifications


  I just completed my R-4B modifications.  For those not previously tuned in, I 
was interested in adding the Sherwood R-4C power supply and audio amp mod to 
the R-4B.  The stock high-voltage dividers, power transformer, and audio output 
tube were all contributing far too much heat for my comfort level although I'm 
sure thousands of R-4Bs have been running just fine.  A side benefit to the 
heat reduction is less change of temperature to the PTO as the bulk of 
generated heat exists very close to the PTO.  I could have just as easily 
installed a small fan but this seemed like a more efficient alternative.

  When I started, I thought this would be a "slam dunk" project.  It wasn't -- 
far from it.  The changes needed result in extensive circuit changes to the 
R-4B. 

  The Sherwood PS board requires a low voltage AC source but neither the 6V nor 
12V filament supplies will work for several reasons, one of which is that 
neither will produce enough voltage to feed the Sherwood board's CT full-wave 
rectifier and 7812 regulator.  The 7812 requires at least 3V of in/out 
differential and then one must add 1 volt for "brown-out" conditions.  A bridge 
rectifier wouldn't be enough without a "kludgey" doubler added.  

  I explored several alternatives, including finding another off-the shelf 
transformer but nothing would fit within the space allowed on the chassis.   
Finally, I ended up replacing the R-4B power transformer with a NOS R-4C 
transformer.  

  Oh, wait a minute -- the R-4B uses a mix of 6V and 12V tubes.  The R-4C only 
uses 6v tubes from a single filament secondary.  Luckily, I was able to find 
all 6V equivalents for five 12V tubes.  For example, the 12BA6 is now a 6BA6, a 
12AX7 is now a 6AX7.  I could have left the 12AX7 as Garey, K4OAH pointed out 
to me, the 12AX7 is designed with a center-tapped filament.  So, a change at 
the tube socket world have worked but I did find a 6AX7 and left the socket 
alone.

  http://72.52.250.47/images/R4B-1.jpg

  This worked well since the secondary winding needed for the Sherwood board 
was now there and the R-4B would now have only 6V tubes of the exact same 
performance parameters as their 12v counter-parts.  

  The R-4C transformer is not a direct replacement.  Mounting centers are 
slightly different -- enough that I had to drill two new chassis holes. With 
the transformer installed, it was time to install the Sherwood PS Board and new 
audio amp:

  http://72.52.250.47/images/R4B-3.jpg

  It took several iterations to get these boards to fit in a way that would 
minimize wiring and stay out of harms way of B+, the headphone jack, and other 
existing hardware.

  The next photo shows changes to the transformer wiring:

  http://72.52.250.47/images/R4B-4.jpg

  Note in the photos that with all this work being done, I felt it a good idea 
to change the main power supply filter cap .  I replaced it with a direct 
replacement from HayseedHamfest.com -- and all paper caps were changed to 
metalized Polypropylene "yellow jackets."   Wiring isn't final and several 
solder connections need TLC.  Also, anti-vox is not yet re-connected to the 
headphone jack, but that's the last item on the list. 

  Another potentially troublesome issue goes back to the voltage dividers for 
low-voltage biasing/switching of three circuits in the R-4B.  By replacing the 
heat-generating voltage-dividers, a common 7812 regulator now feeds these 
circuits but care must be taken to ensure ample isolation.  Each circuit comes 
right back to the 7812 -- no daisy-chains and generous use of 100 ohm series 
isolation resistors with film bypass caps were used on these lines.  So far, so 
good.  

  Hard to believe, but after this much wiring change, it all worked the first 
time.  I was prepared to spend a full day troubleshooting.  Instead, I was 
listening to QSOs in five minutes!  That's a first for me and is probably the 
result of taking about six weeks in time bits to methodically go through each 
and every connection -- then check and cross-check against the schematic.  

  The R-4B now runs incredibly cool now -- the same as a Sherwood modified R-4C 
which isn't too surprising.  Audio from the Sherwood AMP-4 board is strong 
without hiss or other artifacts.  Low-end response was extended by changing 
C187 by a factor of 10X.  This cap is just ahead of the AF volume control.  In 
its stock form with 0.1 uF looking into approx.  2.5K (depending on the wiper 
arm position), the - 3dB point calculates to 650 Hz.  This number is confirmed 
by measurement and is the primary reason why the R-4B sounds a bit thin on the 
low end.  

  W

[Drakelist] R-4B Modifications

[Paul Christensen]

I just completed my R-4B modifications.  For those not previously tuned in, I 
was interested in adding the Sherwood R-4C power supply and audio amp mod to 
the R-4B.  The stock high-voltage dividers, power transformer, and audio output 
tube were all contributing far too much heat for my comfort level although I'm 
sure thousands of R-4Bs have been running just fine.  A side benefit to the 
heat reduction is less change of temperature to the PTO as the bulk of 
generated heat exists very close to the PTO.  I could have just as easily 
installed a small fan but this seemed like a more efficient alternative.

When I started, I thought this would be a "slam dunk" project.  It wasn't -- 
far from it.  The changes needed result in extensive circuit changes to the 
R-4B. 

The Sherwood PS board requires a low voltage AC source but neither the 6V nor 
12V filament supplies will work for several reasons, one of which is that 
neither will produce enough voltage to feed the Sherwood board's CT full-wave 
rectifier and 7812 regulator.  The 7812 requires at least 3V of in/out 
differential and then one must add 1 volt for "brown-out" conditions.  A bridge 
rectifier wouldn't be enough without a "kludgey" doubler added.  

I explored several alternatives, including finding another off-the shelf 
transformer but nothing would fit within the space allowed on the chassis.   
Finally, I ended up replacing the R-4B power transformer with a NOS R-4C 
transformer.  

Oh, wait a minute -- the R-4B uses a mix of 6V and 12V tubes.  The R-4C only 
uses 6v tubes from a single filament secondary.  Luckily, I was able to find 
all 6V equivalents for five 12V tubes.  For example, the 12BA6 is now a 6BA6, a 
12AX7 is now a 6AX7.  I could have left the 12AX7 as Garey, K4OAH pointed out 
to me, the 12AX7 is designed with a center-tapped filament.  So, a change at 
the tube socket world have worked but I did find a 6AX7 and left the socket 
alone.

http://72.52.250.47/images/R4B-1.jpg

This worked well since the secondary winding needed for the Sherwood board was 
now there and the R-4B would now have only 6V tubes of the exact same 
performance parameters as their 12v counter-parts.  

The R-4C transformer is not a direct replacement.  Mounting centers are 
slightly different -- enough that I had to drill two new chassis holes. With 
the transformer installed, it was time to install the Sherwood PS Board and new 
audio amp:

http://72.52.250.47/images/R4B-3.jpg

It took several iterations to get these boards to fit in a way that would 
minimize wiring and stay out of harms way of B+, the headphone jack, and other 
existing hardware.

The next photo shows changes to the transformer wiring:

http://72.52.250.47/images/R4B-4.jpg

Note in the photos that with all this work being done, I felt it a good idea to 
change the main power supply filter cap .  I replaced it with a direct 
replacement from HayseedHamfest.com -- and all paper caps were changed to 
metalized Polypropylene "yellow jackets."   Wiring isn't final and several 
solder connections need TLC.  Also, anti-vox is not yet re-connected to the 
headphone jack, but that's the last item on the list. 

Another potentially troublesome issue goes back to the voltage dividers for 
low-voltage biasing/switching of three circuits in the R-4B.  By replacing the 
heat-generating voltage-dividers, a common 7812 regulator now feeds these 
circuits but care must be taken to ensure ample isolation.  Each circuit comes 
right back to the 7812 -- no daisy-chains and generous use of 100 ohm series 
isolation resistors with film bypass caps were used on these lines.  So far, so 
good.  

Hard to believe, but after this much wiring change, it all worked the first 
time.  I was prepared to spend a full day troubleshooting.  Instead, I was 
listening to QSOs in five minutes!  That's a first for me and is probably the 
result of taking about six weeks in time bits to methodically go through each 
and every connection -- then check and cross-check against the schematic.  

The R-4B now runs incredibly cool now -- the same as a Sherwood modified R-4C 
which isn't too surprising.  Audio from the Sherwood AMP-4 board is strong 
without hiss or other artifacts.  Low-end response was extended by changing 
C187 by a factor of 10X.  This cap is just ahead of the AF volume control.  In 
its stock form with 0.1 uF looking into approx.  2.5K (depending on the wiper 
arm position), the - 3dB point calculates to 650 Hz.  This number is confirmed 
by measurement and is the primary reason why the R-4B sounds a bit thin on the 
low end.  

Was it all worth it?  For me, I suppose it was.  I detest cabinet heat.  
However, had I known all the complicating issues and extensive re-wiring 
needed, I would not have done this since the thought was the Sherwood mod would 
have been "plug 'n play."  This said, I do believe this is the 'right" way of 
distributing low voltages in receivers.  In fairness to Drake, compact ICs 

Re: [Drakelist] [DrakeRadio] Replacing the Power Supply Electrolyic Filter Capacitors, The Brute Force Way

[Paul Christensen]

Drake R-4C power transformer wanted in working condition.  If you have one from 
a parts set, please send private reply.  Tnx!

Paul, W9AC
 ___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake R-4B

[Paul Christensen]

Gary,

I find that putting modifications together on paper isn't the problem --  
what's tough is documenting everything well enough so that I can go back 
some time later and not look at it like it's the first time.   What seems 
trivial on paper during this exercise has resulted in something like 50 
wires all unterminated.  You would not want to see this R-4B right now.  I 
am using tye-wraps with label flags to later help me understand where the 
wire comes from and where it's going.  In the past, I've started projects 
like this only to come back a month later and it looked like someone else's 
work until began to re-familiarize myself with all the changes.


I think the only tricky part to this mod is ensuring that R130 is adequately 
bypassed on both sides of the resistor with short, low-Z connections from 
film caps to ground.  +12V that feeds the new AF amp will also be used to 
activate the BFO at Q6.  C173 is definitely there for a reason and it's not 
just filtering.  As long as I'm cognizant of this limitation, it should be 
fine.  Worst case will be to add a dedicated 7812 for the BFO. 
Characteristic of Drake, the present +12V to Q6 is dropped from a lossy 
divider network (R136, R137) from +150V and yeah it sure gets hot too.


I'm also going to experiment with increasing C187 from 0.1 uF to 1.0 uF. 
The present -3 dB turnover point (0.1 uF into 3K) calculates to a low end 
audio response of 530 Hz.  It's actually a function of the AF control wiper 
arm location looking into the base of Q7 but that's the best case.  So, at 
250 Hz, audio is already down almost 10 dB.  250 Hz is about the lower limit 
of reasonable communications audio quality.  I like to hit 100 Hz, when 
possible and when the receiver's IF filtering will allow it.   If increasing 
C187 introduces too much hum into the receiver's audio, I'll settle for a 
cap value in between.


BTW, thanks for the info on the neon lamp!

Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake R-4B

[Paul Christensen]

Ran into another subtle issue with my R-4B.  The neon dial lamp would not 
fire when the R-4B was plugged into inrush limiter (sold by Electric Radio 
Mag.)  Since DC is used on the lamp, only one of the two elements glows. 
The fix?  I could have replaced the lamp, but I simply swapped the neon lamp 
leads on the PCB.  Now, the other side has a turn at glowing for the next 45 
years.  This may be old news, but a new discovery for me...


The R-4B is now in pieces on the bench.  I'm about half-way complete with 
installing the Sherwood Power Supply upgrade and Sherwood AF amp.  The job 
isn't quite as seamless as it is with the R-4C, but with a few changes, it 
should work fine.  There's little to be gained with the Sherwood PS board 
except that it contains some parts to assist with the addition of a 7812 
regulator needed for the Sherwood AF amp.  The old PS board was pretty well 
cooked but perfectly usable.


The power transformer is leaving its home on the chassis and is being 
mounted on a separate Bud chassis with AC controlled from the R-4B power 
switch. An eight- conductor cable is being constructed to handle the 
filament current.  I had a Helluva' time finding multi-conductor cable by 
the foot -- so I've made my own using individual #18 AWG wire and ultraflex 
3M heat-shrink tubing.  Will probably use a Cinch-Jones connector on the new 
transformer chassis, or Molex.  Between the power transformer and AF output 
tube, my R-4B runs like a furnace -- and too close to the PTO for my comfort 
level.  After the changes, the cabinet temperature should drop down close to 
a Sherwood-modified R-4C.


I'll post links to photos after completion.

Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4B Front Panel Wanted from 4CFrontPanels.com

[Paul Christensen]

Looking for one of Tony Mills' replacement front panels for the R-4B.  If 
you have a new one that's excess to your needs, please let me know.  Tnx!


Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake R-4B

[Paul Christensen]

Gary & Mark, K4SO.

Got it.  Turned the set upside down and the flat retention spring came out 
of "God knows where."  Whew...don't want to re-live that again.


Tnx for the help.

Paul , W9AC

- Original Message - 
From: "Garey Barrell" 

To: "drakelist" 
Sent: Friday, February 25, 2011 2:01 PM
Subject: Re: [Drakelist] Drake R-4B





Paul Christensen wrote:
Now I've done it.  After a complete cleaning of the R-4B front panel and 
associated hardware I cannot get the crystal select switch shaft to 
engage onto the switch shaft.  A brass coupler is used to join the two 
pieces but I failed to look closely at the relationship between the 
coupling and the two shafts.  Each shaft has a flattened end but I see no 
what to synchronize them with the brass coupling -- it just spins.  It's 
as if there's another part that I cannot account for.


The ACCY BAND switch is a one piece shaft.  Are you speaking of the 
Passband Tuner shaft??  I believe there should be a flat piece of steel 
sheet inside the coupling to 'flatten' one side.  I don't have a "B" open 
at the moment.  Perhaps someone else can comment?


I also found a small curved washer which goeswhere?  The larger 
curved washer is placed on the VFO shaft and I'm fine there.


The small curved washer probably goes over the red button on the MAIN 
TUNING window, between the window and the front panel, to hold the window 
in place.





73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake R-4B

[Paul Christensen]

Now I've done it.  After a complete cleaning of the R-4B front panel and 
associated hardware I cannot get the crystal select switch shaft to engage 
onto the switch shaft.  A brass coupler is used to join the two pieces but I 
failed to look closely at the relationship between the coupling and the two 
shafts.  Each shaft has a flattened end but I see no what to synchronize 
them with the brass coupling -- it just spins.  It's as if there's another 
part that I cannot account for.


I also found a small curved washer which goeswhere?  The larger curved 
washer is placed on the VFO shaft and I'm fine there.


Thanks in advance for any help to get me out of this rut.  Gr...

Paul, W9AC


- Original Message - 
From: "Garey Barrell" 

To: "drakelist" 
Sent: Friday, February 25, 2011 10:18 AM
Subject: Re: [Drakelist] Drake R-4B



Paul -

Ripple on Calibrator signal probably power supply ripple, D6, C190, C192.

S-Meter drift is gassy tube (grid emission) probably V4 or V5, possibly 
V1.


Phones jack 'used' to be on the front panel, but interfered with the 
controls on either side.  Note small circle where phones jack USED to be. 
The hole IS in the subchassis as well, so if you want it there, yours 
won't be the first to have it!


AGC SLOW cap is C109.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:
Now that my Drake 1A restoration is complete, it's off to the races with 
a recently-acquired R-4B.  BTW, Hartzell re-painted the 1A cabinet and it 
looks great.  Also, Tom at HayseedHamfest.com provided me with an exact 
replacement multi-section PS cap for the 1A, although it's not listed on 
his website.  Ready for this?  The can is made from copper and looks 
great against the copper chassis.  Perfect retrofit without any hassles.


My first R-4B operating impressions below.  Keep in mind this unit 
requires some TLC.


- Plenty of sensitivity on all bands.  Easily peaks noise with no antenna 
connected;


- High IMD on audio.  Listening to the Xtal calibrator, I hear IMD that 
sounds like perhaps either 60 Hz or 120 Hz is mixing somewhere.  It may 
also be the result of B-H distortion from the output transformer into 
high quality headphones with a 40-ohm load Z.  In any event, I need to 
investigate further.  Overall audio passband response is mediocre.  I was 
expecting a wider audio passband.  At this early stage of ownership, the 
audio is nowhere near the quality of my 1A nor R-4C with Sherwood AF 
mods;


- Audio output tube way too microphonic.  I do not sense this much 
mechanical sensitivity with the 1A receiver and the output stages are 
similar;


- The S-Meter starts at S8 then drifts to down to S0 after about five 
minutes warm up.  Is this behavior normal for the R-4B?  Either a weak 
tube in the AGC loop, leaky cap, or out-of-tolerance resistor changing 
value with heat may be the root cause.  More investigating needed...;


- Why the headphone jack on the side and not on the front panel?  A 
target point is marked on the panel for a 1/4-inch jack and the chassis 
easily supports it.  Very strange;


- AGC *way* too fast on both settings.  Just my opinion, but AGC Slow is 
more like where I would want the Fast setting.  AGC Slow needs R/C help 
to get its recovery slower.   Easy enough to fix;


- Nice VFO feel, even better than early R-4Cs, and equal in tuning feel 
to late R-4Cs with metal/Nylon gears.  Excellent PTO stability.


I would appreciate any comments on the recovered audio and S meter 
abnormalities before digging in.  Many Tnx to everyone on this list!


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake R-4B

[Paul Christensen]

Gary,

Many tnx for the feedback!

Paul, W9AC

- Original Message - 
From: "Garey Barrell" 

To: "drakelist" 
Sent: Friday, February 25, 2011 10:18 AM
Subject: Re: [Drakelist] Drake R-4B



Paul -

Ripple on Calibrator signal probably power supply ripple, D6, C190, C192.

S-Meter drift is gassy tube (grid emission) probably V4 or V5, possibly 
V1.


Phones jack 'used' to be on the front panel, but interfered with the 
controls on either side.  Note small circle where phones jack USED to be. 
The hole IS in the subchassis as well, so if you want it there, yours 
won't be the first to have it!


AGC SLOW cap is C109.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs



Paul Christensen wrote:
Now that my Drake 1A restoration is complete, it's off to the races with 
a recently-acquired R-4B.  BTW, Hartzell re-painted the 1A cabinet and it 
looks great.  Also, Tom at HayseedHamfest.com provided me with an exact 
replacement multi-section PS cap for the 1A, although it's not listed on 
his website.  Ready for this?  The can is made from copper and looks 
great against the copper chassis.  Perfect retrofit without any hassles.


My first R-4B operating impressions below.  Keep in mind this unit 
requires some TLC.


- Plenty of sensitivity on all bands.  Easily peaks noise with no antenna 
connected;


- High IMD on audio.  Listening to the Xtal calibrator, I hear IMD that 
sounds like perhaps either 60 Hz or 120 Hz is mixing somewhere.  It may 
also be the result of B-H distortion from the output transformer into 
high quality headphones with a 40-ohm load Z.  In any event, I need to 
investigate further.  Overall audio passband response is mediocre.  I was 
expecting a wider audio passband.  At this early stage of ownership, the 
audio is nowhere near the quality of my 1A nor R-4C with Sherwood AF 
mods;


- Audio output tube way too microphonic.  I do not sense this much 
mechanical sensitivity with the 1A receiver and the output stages are 
similar;


- The S-Meter starts at S8 then drifts to down to S0 after about five 
minutes warm up.  Is this behavior normal for the R-4B?  Either a weak 
tube in the AGC loop, leaky cap, or out-of-tolerance resistor changing 
value with heat may be the root cause.  More investigating needed...;


- Why the headphone jack on the side and not on the front panel?  A 
target point is marked on the panel for a 1/4-inch jack and the chassis 
easily supports it.  Very strange;


- AGC *way* too fast on both settings.  Just my opinion, but AGC Slow is 
more like where I would want the Fast setting.  AGC Slow needs R/C help 
to get its recovery slower.   Easy enough to fix;


- Nice VFO feel, even better than early R-4Cs, and equal in tuning feel 
to late R-4Cs with metal/Nylon gears.  Excellent PTO stability.


I would appreciate any comments on the recovered audio and S meter 
abnormalities before digging in.  Many Tnx to everyone on this list!


Paul, W9AC





___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Drake R-4B

[Paul Christensen]

Now that my Drake 1A restoration is complete, it's off to the races with a 
recently-acquired R-4B.  BTW, Hartzell re-painted the 1A cabinet and it 
looks great.  Also, Tom at HayseedHamfest.com provided me with an exact 
replacement multi-section PS cap for the 1A, although it's not listed on his 
website.  Ready for this?  The can is made from copper and looks great 
against the copper chassis.  Perfect retrofit without any hassles.


My first R-4B operating impressions below.  Keep in mind this unit requires 
some TLC.


- Plenty of sensitivity on all bands.  Easily peaks noise with no antenna 
connected;


- High IMD on audio.  Listening to the Xtal calibrator, I hear IMD that 
sounds like perhaps either 60 Hz or 120 Hz is mixing somewhere.  It may also 
be the result of B-H distortion from the output transformer into high 
quality headphones with a 40-ohm load Z.  In any event, I need to 
investigate further.  Overall audio passband response is mediocre.  I was 
expecting a wider audio passband.  At this early stage of ownership, the 
audio is nowhere near the quality of my 1A nor R-4C with Sherwood AF mods;


- Audio output tube way too microphonic.  I do not sense this much 
mechanical sensitivity with the 1A receiver and the output stages are 
similar;


- The S-Meter starts at S8 then drifts to down to S0 after about five 
minutes warm up.  Is this behavior normal for the R-4B?  Either a weak tube 
in the AGC loop, leaky cap, or out-of-tolerance resistor changing value with 
heat may be the root cause.  More investigating needed...;


- Why the headphone jack on the side and not on the front panel?  A target 
point is marked on the panel for a 1/4-inch jack and the chassis easily 
supports it.  Very strange;


- AGC *way* too fast on both settings.  Just my opinion, but AGC Slow is 
more like where I would want the Fast setting.  AGC Slow needs R/C help to 
get its recovery slower.   Easy enough to fix;


- Nice VFO feel, even better than early R-4Cs, and equal in tuning feel to 
late R-4Cs with metal/Nylon gears.  Excellent PTO stability.


I would appreciate any comments on the recovered audio and S meter 
abnormalities before digging in.  Many Tnx to everyone on this list!


Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4A amplifier

[Paul Christensen]

Can audio be feed out of the R-4A bypassing the onboard amplifier?


Yes, you can bypass the internal AF amp stages for headphone/speaker audio, 
but they must remain active (see below).  I do this with a Marantz 1030C. 
The following mod is easily reversible without leaving no permanent 
"residue" in the event of a future sale.


1) Add a 1.0 uF cap, positive end to the AF GAIN wiper arm;
2) Connect a length of shielded audio cable to the other end of the new cap, 
shield to the chassis;
3) Disconnect the existing wiring to the RCA SPKR jack (dress it so that it 
can be easily restored); and
4) Connect the other end of the new shielded audio cable to the RCA SPKR 
jack, shield to the chassis.


With this change, the R-4A's AF GAIN control will still remain active to the 
external audio amp.  Headphone and speaker audio comes from the new external 
amp. Tube V7 must remain in its socket for ANTI-VOX operation. The new cap 
can be either a low ESR electrolytic or tantalum type.  If you're an 
audiophile, you'll use the former.  Myself, I have no issues using 
inter-stage tantalum coupling caps for "communications audio."


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] GUF-1 Filter

[Paul Christensen]

I'm planning on adding a GUF-1 filter to my R-4C receiver.  Any comments as 
to the selection of either the 6 kHz or 8 kHz filter version of the GUF-1? 
One comment on the web indicated that the 4NB is more effective with the 8 
kHz GUF-1.  Perhaps it's a decision that balances NB effectiveness versus 
narrower Rx bandwidth.


Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake 1A Progress

[Paul Christensen]

Although that's how it is addressed in the articles, it's not just an 
audio

problem.


Jim, let's take this off-line and we can bring K9YC into the discussion. 
Thanks.


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake 1A Progress

[Paul Christensen]

It's all part of the same big picture.


The Pin 1 problem discussed by Muncy and Brown refers to the incorrect use 
of audio shielding when the cable shielding bypasses the equipment chassis 
and relies only upon circuit ground.


I'm discussing RF shield connectivity -- not audio.  Moreover, I am not 
advocating the abandonment of the chassis for the SO-239.  Rather, the 
chassis should not be the basis of the only RF ground return from the 
SO-239.  Mil-Spec equipment not only makes use of the chassis ground but 
also brings the RF coax shield all the way to the chassis connector.  The 
better equipment manufacturers (e.g., Mil-Spec) do not rely on a path of 
sheet metal, screws, and other hardware to ensure a low impedance RF path --  
only to have that pathway deteriorate with time in less than ideal operating 
environments.


The inclusion of the coaxial braid onto the SO-239 has no relevancy in and 
of itself to the Pin 1 audio problem.


Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake 1A Progress

[Paul Christensen]

There are very good reasons for the chassis to function as a ground 
return. Do

a Google search on "the pin 1 problem".


This is very different than the "PIN 1" problem addressed by Jim, K9YC and 
others.


Paul, W9AC


- Original Message - 
From: "Jim Shorney" 

To: 
Sent: Thursday, January 27, 2011 8:11 PM
Subject: Re: [Drakelist] Drake 1A Progress



On Thu, 27 Jan 2011 17:52:42 -0500, Paul Christensen wrote:


I have never been a believer in allowing the chassis to function as an RF
ground return, especially on SO-239 connectors.  Those connectors really
need their own reliable return path to a solid circuit ground point.  Not
sure how that practice started or when...




73

-Jim


--
Ham Radio NU0C
Lincoln, Nebraska, U.S.S.A.
TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, 
GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time!


"Give a man a URL, and he will learn for an hour; teach him to Google, and 
he will learn for a lifetime."


HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/
http://incolor.inetnebr.com/jshorney
http://www.nebraskaghosts.org



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Drake 1A Progress

[Paul Christensen]

Been diagnosing somewhat low sensitivity on my Drake 1A.  I think I reported 
here that I replaced all suspect paper caps with metalized Polypropylene 
"yellow jacket" types.  I saw no improvement with the new caps.  In a 
nutshell, loss of gain was affected by the severe drift of two 33K 
carbon-composition resistors, one on the screen of V2, the other on the 
screen of V4.  Both resistors drifted up to about 105K.  I replaced both 
with 1/2W carbon film types and wow, what a difference!  Now, I need to use 
that darned 30dB attenuator even on the high bands!  Proper screen voltage 
is an absolute must in the early RF and IF stages in order to extract 
required gain.  I can now think of a few other boatanchors of mine that 
likely need the same treatment.


Other resistors, (including other values of screen resistors on the other 
tubes) are off a bit as expected since the set is 50 years old, but for some 
reason the 33K resistors drifted way out there.  So, I highly recommend that 
1A owners check those values to determine if they've drifted.


Had another quirk:  As I rotated the antenna trim, I noticed that Rx 
sensitivity would change if I gently pushed the control.  I noticed that the 
ground frame of the air cap trimmer is connected to a small copper mounting 
plate. That plate is connected to yet another plate, and that plate is 
connected to the chassis, relying only on the hardware to make for a low 
impedance
connection to circuit ground.  Rather than fight the copper and hardware 
corrosion, I noticed that the trim cap has an unused solder tab on its 
ground frame.  Easy fix:  Just bring the tab down and solder it the mid 
plate.  I then soldered the mid plate to the copper chassis.  Problem gone. 
Sure makes soldering easy when the chassis parts are all copper!


I have never been a believer in allowing the chassis to function as an RF 
ground return, especially on SO-239 connectors.  Those connectors really 
need their own reliable return path to a solid circuit ground point.  Not 
sure how that practice started or when...


Darn, I almost forgot how easy it is to troubleshoot VT receivers since so 
many parts are unterminated at the VT.  Unlike solid-state circuits, few 
parts require removal of one end. That greatly accelerates the 
troubleshooting process.


Also, I am going to add a 110V Zener diode at the VFO's 105VDC B+ line.  The 
current limiting resistor is already there going back to the +105V rail.  My 
utility AC lines voltage runs high at 125V so using a Variac, I dropped the
AC line voltage down to see where I achieved 105VDC.   It occurs about 
110VAC.  I'm doing this to help stabilize the VFO by better regulating B+. 
The 105V supply rail from the PS only goes to the VFO, although it's part of
a resistive divider feeding B+ to other tubes.  I doubt it will help too 
much as other circuit factors likely mask any improvement, but it does seem 
like the right thing to do.


About a year ago, I purchased a couple inrush limiters from Electric Radio 
Magazine.  They do a nice job of bringing back high utility voltage down to 
about 115V where this equipment really belongs.  I could add the same 
circuit to the receivers, but the external solution is non-invasive and 
probably helps to preserve the value of the 1A.


Paul, W9AC



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake 1A Coil Slugs

[Paul Christensen]

Tnx for the many private replies from this list and the Boatanchors list.  From 
the number of replies, it's normal for most of the antenna band slugs at L1 to 
be missing in the 20m-10m slots.  One owner had them in 80m-20m, then missing 
in 15m-10m.  So, I suspect this was determined during production of the 1A.

Paul, W9AC
  - Original Message - 
  From: Grant Youngman 
  To: Tom Evans, AG9X 
  Cc: drakelist 
  Sent: Sunday, January 16, 2011 9:37 PM
  Subject: Re: [Drakelist] Drake 1A Coil Slugs


  I'd have to pull mine out and open it to be sure, but my recollection is that 
there are no slugs in those antenna coils. 


  Grant/NQ5T

  Sent from my iPod

  On Jan 16, 2011, at 7:51 PM, "Tom Evans, AG9X"  wrote:


Paul,

I took a look at the schematic and don't see slugs indicated for 20 - 10 M. 
 If they were originally present but now missing, I'm guessing you'd not be 
able to peak the antenna trim cap for maximum band noise on those bands.

Hopefully someone with a 1A will respond.

-Tom, AG9X




    On Sun, Jan 16, 2011 at 7:39 PM, Paul Christensen  wrote

  Upon further investigation of the Drake 1A schematic, it appears the 
antenna coils are tuned to resonate with the antenna trim cap such that the 
trim cap is at mid range in the center of each respective band.  This is 
necessary on 80m and 40m, but spanning the band from edge-to-edge on 20m 
through 10m does not involve much change of the trim control.

  I'm beginning to think (perhaps wishfully?) that the slugs were never 
there in the first place.  Anyone have a Drake 1A that can take peek through 
the perforated cover?  Tnx!

  Paul, W9AC

  - Original Message - From: "Paul Christensen" 
  To: 
  Sent: Sunday, January 16, 2011 8:23 PM
  Subject: [Drakelist] Drake 1A Coil Slugs




I recently acquired a Drake 1A receiver in nice condition except that 
three coil slugs are missing in the 20,15, and 10m antenna coils.  It appears 
Drake used the same slug and phenolic coil assembly for all coils in the 1A.

I've seen these used a million times before: It's a round ferrite slug 
with a straight blade slot on one end of the ferrite core. The other end of the 
ferrite is attached to a long bass screw.  The mating phenolic coil form 
assembly is the type that just snaps into the chassis.

I now it's a longshot, but anyone know a source?  Is it possible they 
simply were not used on the 20m-10m ant coils?

Paul, W9AC

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Drake 1A Coil Slugs

[Paul Christensen]

Upon further investigation of the Drake 1A schematic, it appears the antenna 
coils are tuned to resonate with the antenna trim cap such that the trim cap 
is at mid range in the center of each respective band.  This is necessary on 
80m and 40m, but spanning the band from edge-to-edge on 20m through 10m does 
not involve much change of the trim control.


I'm beginning to think (perhaps wishfully?) that the slugs were never there 
in the first place.  Anyone have a Drake 1A that can take peek through the 
perforated cover?  Tnx!


Paul, W9AC

- Original Message - 
From: "Paul Christensen" 

To: 
Sent: Sunday, January 16, 2011 8:23 PM
Subject: [Drakelist] Drake 1A Coil Slugs


I recently acquired a Drake 1A receiver in nice condition except that three 
coil slugs are missing in the 20,15, and 10m antenna coils.  It appears 
Drake used the same slug and phenolic coil assembly for all coils in the 
1A.


I've seen these used a million times before: It's a round ferrite slug 
with a straight blade slot on one end of the ferrite core. The other end 
of the ferrite is attached to a long bass screw.  The mating phenolic coil 
form assembly is the type that just snaps into the chassis.


I now it's a longshot, but anyone know a source?  Is it possible they 
simply were not used on the 20m-10m ant coils?


Paul, W9AC

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] Drake 1A Coil Slugs

[Paul Christensen]

I recently acquired a Drake 1A receiver in nice condition except that three 
coil slugs are missing in the 20,15, and 10m antenna coils.  It appears 
Drake used the same slug and phenolic coil assembly for all coils in the 1A.


I've seen these used a million times before: It's a round ferrite slug with 
a straight blade slot on one end of the ferrite core. The other end of the 
ferrite is attached to a long bass screw.  The mating phenolic coil form 
assembly is the type that just snaps into the chassis.


I now it's a longshot, but anyone know a source?  Is it possible they simply 
were not used on the 20m-10m ant coils?


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] (no subject)

[Paul Christensen]

Chuck,

My plan is to bring audio out to an unused RCA jack that can be restored later 
if necessary.  I have a modified Marantz 1030 integrated amp.  It's modified so 
that the "balance" control is now a fader control.  The MONO button bridges the 
two channels together.  Why would I do this?  Part of the same plan is to slave 
another R-4C using the VFO from the first R-4C.  This will alow for true 
diversity reception and also offer an other DX split option.  Clifton labs 
buffer amps will isolate the VFO lines.

I'll tap the high side of the existing R-4C AF controls with a 1 uF cap to the 
Marantz 1030 where its input Z is about 2K ohm.  In addition to being a Hi-Fi 
amp, the Marantz will form the control center for the two R-4Cs.

For your purpose, I would also tap the high side of the R-4C AF control with a 
1 uF cap on its way out the back to the Hi-Fi amp of your choice.  If you still 
want to use the R-4C AF control, simply tap the coupling cap to the AF 
control's wiper arm.  Just ensure that the amp has a moderately high input Z.  
Most consumer equipment uses a Z of about 2k ohm.  The lower the input Z of the 
amp, the larger the coupling cap value required.

Paul, W9AC   
  - Original Message - 
  From: Chuck Pool 
  To: drakelist@zerobeat.net 
  Sent: Wednesday, December 01, 2010 11:55 AM
  Subject: [Drakelist] (no subject)


Hi to all Drake fans:


Do you think the Drake R-4C could be modified to accommodate one of 
these two class A audio amps and the graphic equalizer?


At present I don't have the schematics for these products.


Here are the three links to look at:



http://cgi.ebay.com/Valve-Class-Tube-Headphone-Amplifier-pre-Bravo-V2-/260697180184?pt=LH_DefaultDomain_0&hash=item3cb2c34818#ht_5958wt_1140





http://cgi.ebay.com/Bravo-V1-Kopfhorerverstarker-Tube-Class-Rohr-GE1-/260701027235?pt=LH_DefaultDomain_77&hash=item3cb2fdfba3#ht_6316wt_1140





http://cgi.ebay.com/Bravo-Tube-Headphone-Amplifier-V3-EQ-Equalizer-valve-US-/260677485333?pt=LH_DefaultDomain_0&hash=item3cb196c315#ht_3975wt_1176


73,
Chuck - AA5WG
Cedar, Michigan U.S.A. 




--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] L4-B Power Switch

[Paul Christensen]

This is a resource for a long-term fix, once the switch is repaired:

http://www.w8zr.net/vintage/amplifiers/Drake%20L4B%20Modification/Drake%20L-4B%20Modification.htm

Paul, W9AC

- Original Message - 
From: "Wayne Rogers" 

To: "James Bridgers" ; 
Sent: Tuesday, November 09, 2010 7:03 PM
Subject: Re: [Drakelist] L4-B Power Switch


Jim:  See the following: 
http://www.wb4hfn.com/DRAKE/DrakeArticles/L4B-SW/L4B-Switch01.htm


You might be able to restore your switch.

Wayne N1WR

--
From: "James Bridgers" 
Sent: Tuesday, November 09, 2010 6:34 PM
To: 
Subject: [Drakelist] L4-B Power Switch


Greetings All,
Well it had to happen sooner or later, but I would prefer later.  Anyway 
what to do when the power switch on the L4-B in not repairable?  Anyone 
got any suggestions?


Thanks in advance for your help

73 All
Rod N4BNO

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Notch Control

[Paul Christensen]

Hi Richard,

I tried to access the core from the back of the assembly but at least on 
this R-4C, the top of the slug is smooth with no indentation.   With the 
front panel was removed, turning the core from the front was easy once the 
anti-turn adhesive was broken.  After alignment, I re-applied a drop of 
adhesive to keep it from accidentally turning in the future.


Paul, W9AC



- Original Message - 
From: "Paul Christensen" 

To: "Drakelist group" 
Sent: Wednesday, October 27, 2010 1:49 PM
Subject: Re: [Drakelist] R-4C Notch Control


Yep, that fixed it.  With the front panel removed, I had to turn the 
notch coil shaft CCW by about four turns such that the null occurs when 
the control is at 12 o'clock on zero beat - as discussed in the manual. 
Access to the coil shaft is through a hole in the front chassis, and does 
require panel and knob removal.  Many Tnx!


Paul, W9AC

 I also had problems tuning the notch filter on my R4-B. I was able to 
do it from the back but now don't remember exactly how it did it. I think 
there is a hex socket on the back of the core. Its just been too long and 
I only had to do it once. BTW, this notch filter is _very_ effective when 
adjusted right.



--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Notch Control

[Paul Christensen]

Yep, that fixed it.  With the front panel removed, I had to turn the notch 
coil shaft CCW by about four turns such that the null occurs when the 
control is at 12 o'clock on zero beat - as discussed in the manual.  Access 
to the coil shaft is through a hole in the front chassis, and does require 
panel and knob removal.  Many Tnx!


Paul, W9AC



- Original Message - 
From: "Paul Christensen" 

To: "Drakelist group" 
Sent: Wednesday, October 27, 2010 4:10 PM
Subject: Re: [Drakelist] R-4C Notch Control



Bill & Garey,

Thanks for the feedback.  I'll post my results.

I had figured it was the slug and not another problem since I could begin 
to attain a deep null if I pulled the knob slightly forward, being careful 
not damage anything in the process.  So, it's definitely an 
electro-mechanical problem.


Paul, W9AC

- Original Message - 
From: "Bill Frost" 

To: "Paul Christensen" 
Sent: Wednesday, October 27, 2010 3:49 PM
Subject: Re: [Drakelist] R-4C Notch Control


Hello Paul,

Access from the front, use a bent wire in shape of shepard's hook.  If 
there is red goop on spring shaft, it will turn but with some force. 
Check knob position before adjusting, knob should point to off when drops 
into click.


73, Bill

--- On Wed, 10/27/10, Paul Christensen  wrote:


From: Paul Christensen 
Subject: [Drakelist] R-4C Notch Control
To: "Drakelist group" 
Date: Wednesday, October 27, 2010, 3:39 PM
A prior owner appears to have
tampered with my second R-4C's notch slug. I've opened the
instructions in the owner's manual, but is access to the
slug from the front or back (through the grommet)?
Also, is a plastic flat blade used or hex alignment
tool? Tnx!

Paul, W9AC

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist








___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] R-4C Notch Control

[Paul Christensen]

Bill & Garey,

Thanks for the feedback.  I'll post my results.

I had figured it was the slug and not another problem since I could begin to 
attain a deep null if I pulled the knob slightly forward, being careful not 
damage anything in the process.  So, it's definitely an electro-mechanical 
problem.


Paul, W9AC

- Original Message - 
From: "Bill Frost" 

To: "Paul Christensen" 
Sent: Wednesday, October 27, 2010 3:49 PM
Subject: Re: [Drakelist] R-4C Notch Control


Hello Paul,

Access from the front, use a bent wire in shape of shepard's hook.  If there 
is red goop on spring shaft, it will turn but with some force.  Check knob 
position before adjusting, knob should point to off when drops into click.


73, Bill

--- On Wed, 10/27/10, Paul Christensen  wrote:


From: Paul Christensen 
Subject: [Drakelist] R-4C Notch Control
To: "Drakelist group" 
Date: Wednesday, October 27, 2010, 3:39 PM
A prior owner appears to have
tampered with my second R-4C's notch slug. I've opened the
instructions in the owner's manual, but is access to the
slug from the front or back (through the grommet)?
Also, is a plastic flat blade used or hex alignment
tool? Tnx!

Paul, W9AC

___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist






___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Notch Control

[Paul Christensen]

A prior owner appears to have tampered with my second R-4C's notch slug. 
I've opened the instructions in the owner's manual, but is access to the 
slug from the front or back (through the grommet)?  Also, is a plastic flat 
blade used or hex alignment tool?  Tnx!


Paul, W9AC 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] QRZRe: Blue Filters for B and C lines

[Paul Christensen]

Just finished updating an R-4C with all five Sherwood mods including relay 
selectable 1st IF filters.  Wow, that's a job.  I ended up using Don Buska's 
blue LED replacements after alternating between the gells and the LEDs with 
only the white diffuser to see what looks best.  No comparison.  The blue 
LEDs with only the white diffuser look awfully impressive, especially in a 
darkened shack.  The LEDs will stay.


I have the QSK plans complete and initial testing looks promising.  I am 
routing my R-4C and T-4XC through an Ameritron QSK-5 PIN diode RF switch. 
The QSK-5 was designed for amplifiers without their own internal QSK 
circuit, but it can be adapted for use with classic "separates."  No mods to 
the rig except the Tx's bias line is controlled by the QSK-5 switch and is 
easily reversible.  No other complicated circuits needed.  So, how do I 
establish CW system timing?  The latest generation of CW keyers now offer 
lead-in and lead-out timing parameters on a dedicated PTT output line, 
digitally adjustable in 1ms increments through software or paddle commands. 
From initial tests, QSK is so fast that it sounds like full duplex.  Since 
the C line's VFOs run continuously without constant toggling Tx/Rx CW offset 
shift as is the case of modern, synthesized rigs, QSK can be set blistering 
fast since there's no synthesizer to settle before the switch occurs.   The 
mute line on the R-4C is disengaged, allowing the R-4C to listen to one's 
own transmitted signal, greatly attenuated though the PIN diode switch in 
the QSK-5 to serve as a sidetone.


It's amazing how much cooler the R-4C runs without that inefficient Class-A 
audio amp burning up the air around it.  Next change is to bring out a fixed 
output audio line (capacitively-coupled to the high side of the Volume 
control) for use with a Marantz audiophile-grade integrated audio amp.


I have the R-4C NB option, but just pulled it out of the circuit as the 
system gain is about 6 dB less than without it -- even after adjusting the 
gain pot on the NB.  Is it common to run out of gain range on that pot?  In 
any case, I detest NBs anyway so I don't think I'll miss it.


When the QSK the project is complete, I'll post a block diagram on my 
QRZ.com page.  Folks who have always wanted to run super-fast QSK from the C 
Lines now have an option that does not involve extensive and invasive 
circuit changes.


Paul, W9AC


___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] Blue Filters for B and C lines

[Paul Christensen]

Is blue dial filter material no longer available from Steve, KG9BV?  I need 
a set myself.  My understanding is that WA9TGT stopped supply the material a 
couple years ago.


Paul, W9AC



- Original Message - 
From: "Garey Barrell" 

To: "drakelist" 
Sent: Tuesday, October 19, 2010 9:43 AM
Subject: Re: [Drakelist] Blue Filters for B and C lines



Sorry guys.  Fingers faster than brain.

The correct number is # 172, 'Lagoon Blue' from Lee Lighting.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs



kendw...@netscape.com wrote:
Googled your ref, did not find, there is a 71 and a 172 blue lagoon gel 
sheet, one priced EU @ 4.75 for @ 25 x 125 cm sheet, plus shipping.

FYI
AB1JZ

--- k4...@mindspring.com wrote:

From: Garey Barrell
To: Drakelist@zerobeat.net
Subject: Re: [Drakelist] Blue Filters for B and C lines
Date: Mon, 18 Oct 2010 22:43:47 -0400

Richard -

Lee Lighting #72 'Lagoon Blue' gel.  Used for stage lighting.  Available
by mail, or from a stage lighting / production company.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs



Donley wrote:


What were the filter manufacturers and filter numbers for replacing
the faded green filters on the B and C lines?
Richard
kc9ub




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist 



___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

[Drakelist] R-4C Upgrade Boards

[Paul Christensen]

I have an R-4C I will be selling with a set of upgrade boards but they are 
not from Sherwood (not Sartori either).  As I recall these were sold by a 
"W4" about 15 years ago who may now be SK?  Anyone know more about these 
upgrades?


Paul, W9AC




___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist

Re: [Drakelist] MPN3404 Diode on Filter Board of TR7

[Paul Christensen]

It's a VHF PIN diode with very low junction capacitance.  I have to believe 
Drake used this diode for a reason.  I'm not sure in what part of the circuit 
it's broken, but if it's in an up-conversion area, then I would definitely try 
to stick with the original part number or an equivalent (e.g., MPN3700).

It looks like an obsolete part now, but I see a few for sale at reasonable 
prices at the big on-line auction site.

Paul, W9AC

  - Original Message - 
  From: E VICKNER 
  To: drakelist@zerobeat.net 
  Sent: Monday, July 05, 2010 12:14 PM
  Subject: [Drakelist] MPN3404 Diode on Filter Board of TR7


  I picked up a TR7 yesterday at a hamfest.  Upon opening the radio up I 
noticed that one of the MPN3404 diodes on the filter board had a broken lead.

  Is there anything special about the use of this particular diode of the 
filter board or can I substitute a general purpose switching diode for the 
broken one?

  Tnx & 73  Ed  K2ZE


--


  ___
  Drakelist mailing list
  Drakelist@zerobeat.net
  http://mailman.zerobeat.net/mailman/listinfo/drakelist
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist