Re: [drakelist] R-4B T-4XB question

[Dennis Monticelli]

Hi Jason,

I also noted that CW notes were hum modulated in my R4B.  Because
you remember better performance in the past, perhaps the big can is
going south on you?  I have only worked on two Drakes (a 4A and a
4B) and both of them needed can replacement.  Post replacement,
both radios still had finite residual hum, though much improved from
before.  My R4B is no longer modulating CW notes.  After a
doubling of the capacitance of the first filter section, the hum is now
inaudible.

See my earlier post regarding the 4B and Garey's suggestions for alleviating headphone hum.  

Look for a bulge in the PS can or a hotter than normal can or excessive
ripple on the filter sections.  The first filter section (across
the raw DC) is hammered by the most ripple current and can be expected
to fail first due to localized heat buildup.  If the measured
voltage ripple is much more than about 8Vpp, it should be
replaced.  While you're in there, I would replace the other (less
stressed) sections at the same time.

Denny AE6C
On 11/21/05, Jason Buchanan <[EMAIL PROTECTED]> wrote:
"Jason Buchanan" <[EMAIL PROTECTED]> made an utterance to the drakelist gang--hi,
I fired up my beauties tonight but noticed the receive on the R-4B is not ashot as it used to be.  Receive sensitivity doesn't seem to pull 'em in likeit used to.  It's good but doesn't seem great like it used to be.  Received
CW notes have some hum in them - it's not bad but it's not pure and clean.Listening to the same stations with my Omni 6 proves that the hum is in theR-4B and not the sending station.The AC-4 has some hum in it as well listening to the sound coming from the
cabinet.Just wondering what everyone might recommend for either/all of theseproblems.  I'm pretty handy with my weller soldering station but I have noidea where to start debugging problems with the R-4B especially.  I could
replace the caps in the AC-4 but wondering if there's more than just thecaps that I should replace.  And also wondering if that large can in theR-4B should be replaced.vy 73 Jason N1SU--
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RE: [drakelist] TR7 fan recommendation?

[Jim Shorney]

"Jim Shorney" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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On Mon, 21 Nov 2005 07:14:29 -0500 (EST), Ron Wagner wrote:

>My guess is that Drake never figured you to run high duty cycle modes 
>while mobile.  I would think a RTTY or Slow Scan setup a bit big for 
>a mobile installation in the late 70s :-)  Then again what do I know.

That's probably a good guess, Ron, although the hams at Drake should
have known that hams in the real world are likely to try just about
anything. I'm waiting for Mike to chime in on this one.

-- 
Jim Shorney  -->.<--Put complaints in this box
jshorney (at) inebraska.com
Ham Radio NU0C
Lincoln, NE, USA
EN10ps
http://incolor.inetnebr.com/jshorney/

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Re: [drakelist] Certain R4B's may be factory wired for hum

[Dennis Monticelli]

Thanks for your comments, Garey.  I have read your posts before and found them articulate, authoratative, and useful.

First of all, let me state more accurately the nature of the wiring
error.  The RED lead of the transformer was wired to the second
tag from the chassis wall (as you noted), but the wiring to the two
tags straddled by the 330 ohm were crossed.  Not having seen a
"good" radio, I didn't know what was normal and what was not.  The
fix is either to uncross the wires or rewire the RED lead along with
the 0.005uF across its secondary.  I thought about it and ended up
uncrossing the wires as this was easier to do.

The 330 resistor is being asked to dissipate almost 1/2 watt in my
particular set.  This is because my early serial R4B is wired
differently from the manual in terms of the screen dropping
scheme.  My R4B does not use an independent 10K resistor to do the
job.  Instead it taps directly off R136 (the 1K decoupling
resistor feeding Q7) resulting in a higher screen voltage and thus more
plate current than a later serial set. I believe this was intentional
on Drake's part (saves components) and not a wiring error.  I
measured 47mA of cathode current which translates to a roughly 450mW
burden on the 330 ohm (after accounting for screen current). 
Later serial R4B's are probably wired just like the manual and
handle  350mW as you noted.  Maybe I should re-wire my screen
also (per the manual) so as to allow that 6EH5 to run a bit cooler.

Yes, increasing the capacitance of the first filter cap will increase
the stress on the diodes, but transformers are not nearly so sensitive
to surge currents as semiconductors so it is not in any danger in my
opinion.  The extra surge into the diodes is of the same magnitude
as before (limited by the same winding resistance and not limited by
cap ESR) but lasts twice as long, hence the greater stress.  I
decided it was worth the risk as 8Vpp ripple on top of 160V is kinda
high (5%) by my standards.  Fortunately, I got away with it in
this case.

Your headphone sensitivity and frequency response comments are right
on.  It seems another way to mitigate the problem is to put a
smallish cap in series with the headphones in addition to resistively
attenuating.  It should be possible to make a small dent in the
60Hz response without materially affecting the low end of the audio
response.

Denny AE6COn 11/21/05, Garey Barrell <[EMAIL PROTECTED]> wrote:
Denny -Just one of the reasons PC boards are so popular!  :-)Human beans make misteaksI just happen to have an R-4B open on my desk working on the partslocator CD.  For reference for all of you who are rushing to check your
R-4B...   The RED (plate) wire from the audio output transformer_should_  be connected to the SECOND tag from the chassis wall.Apparently Denny's was connected to the FIRST tag.   Hopefully this isan isolated incident, one of the assemblers being distracted
momentarily!!   It would be interesting to hear if anyone else findsthis error.The resistor probably should be a 1W, this one is dissipating ~ 350 mW.It is snugged up against a terminal strip so has a little "heat
sinking".   This receiver has quite a few hours on it, and the resistorreads 325 ohms, so must not be TOO overloaded.  It certainly would NOTbe an easy replacement!Doubling the size of the input capacitor DOES increase the load on the
power transformer and rectifiers, especially at turn-on.  The only limiton the surge current is the transformer winding resistance.  I have noidea if, in this case, the increase in current is critical or even
significant.  "Generally" it's not a good idea to increase the INPUTcapacitor much over the design value for this reason.Headphone hum is often a result of headphone sensitivity or frequencyresponse.  Phones that are very sensitive can cause the user to operate
the receiver with the AF gain control at a very low level, barely offthe ON-OFF switch.  The causes a problem because the AF stages of thereceiver run "wide open", and the volume is controlled by reducing the
input signal level to the amplifier.  The result is that at very lowvolume settings the "signal to noise ratio" is poor since the "noise" isthe same regardless of signal input level.  Hi-Fi phones are usually
much more objectionable because of their extended low frequencyresponse.   Communication grade phones normally have very little lowfrequency response.  The "fix" is to attenuate the AF output AFTER the
audio stages by either a series resistor or resistive pad to reduce thesensitivity of the phones, allowing the AF Gain control to be set to the10-11 O'clock area for normal volume.73, Garey - K4OAH
AtlantaDrake C-Line Service ManualDennis Monticelli wrote:> I thought I would share my recent experience involving replacing the
> power supply electrolytics in my R4B. Denny  AE6C

[drakelist] transceive R-4B / T-4XB in RCVR position does not produce full output

[Jason Buchanan]

"Jason Buchanan" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--

hi,

I noticed that when I select RCVR on the T-4XB that the output power 
increases as I adjust the preselector on the R-4B, however when I do this I 
can barely hear anything until I turn the preselector back to its optimal 
tuning position.  I remember reading a while back a way to fix this but i'm 
not sure what it was.  I can still get the 100W output I'm looking for but I 
have to crank up the gain on the T-4XB to the 3:00 o'clock position.  If I 
leave them separate and spot them I need only the 11:00 o'clock gain 
position for 100W.


Any ideas?


Thanks Jason N1SU 


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[drakelist] R-4B T-4XB question

[Jason Buchanan]

"Jason Buchanan" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--

hi,

I fired up my beauties tonight but noticed the receive on the R-4B is not as 
hot as it used to be.  Receive sensitivity doesn't seem to pull 'em in like 
it used to.  It's good but doesn't seem great like it used to be.  Received 
CW notes have some hum in them - it's not bad but it's not pure and clean. 
Listening to the same stations with my Omni 6 proves that the hum is in the 
R-4B and not the sending station.


The AC-4 has some hum in it as well listening to the sound coming from the 
cabinet.


Just wondering what everyone might recommend for either/all of these 
problems.  I'm pretty handy with my weller soldering station but I have no 
idea where to start debugging problems with the R-4B especially.  I could 
replace the caps in the AC-4 but wondering if there's more than just the 
caps that I should replace.  And also wondering if that large can in the 
R-4B should be replaced.


vy 73 Jason N1SU

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RE: [drakelist] TR7 fan recommendations

[Gerry]

"Gerry" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
I agree with Garey 100%: it is a SYSTEM. Note the unusual heatsink Drake
used. I have not seen this design used by anyone else. It is obviously
designed for exhaust, just as Garey pointed out. If I remember correctly,
the heatsink design was patented.

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Garey Barrell
Sent: Monday, November 21, 2005 10:42 AM
To: drake
Subject: Re: [drakelist] TR7 fan recommendations


Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
This comes up every once in a while

The fan on the TR-7 should always be mounted to blow air OUT.   A piece
of electronic equipment that is DESIGNED to be fan cooled has a cooling
_SYSTEM_.The TR-7 system is designed for the air to be pulled in
through the slots in the top and bottom of the cabinet and blown OUT via
the fan.   Reversing this flow does not cool the entire transceiver as
effectively.   As for the PTO temperature, the absolute temperature is
not particularly important, rather the change in temperature as the
heatsink heats and cools with transmissions.  Blowing air IN forces the
heated air from the heatsink past the PTO area, causing the PTO
temperature to fluctuate.  The dial lamp that some cite as a source of
PTO drift is actually a constant heat source that helps to stabilize the
PTO area at a slightly higher temp.   There IS a "warmup" time for the
TR-7 for this temperature to stabilize.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual




Floyd Sense wrote:

>
> "Floyd Sense" <[EMAIL PROTECTED]> made an utterance to the drakelist 
> gang
> --
>
> I have a set of temperature probes and will take some readings near 
> the PTO with the fan blowing in and out to see what happens to the 
> temperature. Hard to believe that mounting the fan to blow in, rather 
> than out, would result in less PTO temperature rise.
>
> 73, Floyd - K8AC
>

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Re: [drakelist] TR7 fan recommendations

[Floyd Sense]

"Floyd Sense" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
Nothing to disagree with there!  I was going through the list archives the 
other day looking for info on the fan, and ran across a couple of 
recommendations to mount the fan so that the airflow was in, instead of out. 
One of the proponents of that approach explained that the reason was that 
the fan "blows more air out than it sucks in".  Had he not made that 
statement, I might have thought that there was some merit to the argument!


Thus far, I don't notice any drift other than during the brief warmup 
period.  I always get a charge out of reading the articles that talk about 
how the TR7 isn't suitable for digital modes without some sort of active 
compensation to stabilize the PTO.  I spent many years operating RTTY with 
gear that doesn't come close to the TR7 stability and can't say that I ever 
noticed the difficulties from drift.


73, Floyd - K8AC

- Original Message - 
From: "Garey Barrell" <[EMAIL PROTECTED]>

To: "Floyd Sense" <[EMAIL PROTECTED]>
Cc: "drake" 
Sent: Monday, November 21, 2005 10:36 AM
Subject: Re: [drakelist] TR7 fan recommendations



This comes up every once in a while

The fan on the TR-7 should always be mounted to blow air OUT.   A piece of 
electronic equipment that is DESIGNED to be fan cooled has a cooling 
_SYSTEM_.The TR-7 system is designed for the air to be pulled in 
through the slots in the top and bottom of the cabinet and blown OUT via 
the fan.   Reversing this flow does not cool the entire transceiver as 
effectively.   As for the PTO temperature, the absolute temperature is not 
particularly important, rather the change in temperature as the heatsink 
heats and cools with transmissions.  Blowing air IN forces the heated air 
from the heatsink past the PTO area, causing the PTO temperature to 
fluctuate.  The dial lamp that some cite as a source of PTO drift is 
actually a constant heat source that helps to stabilize the PTO area at a 
slightly higher temp.   There IS a "warmup" time for the TR-7 for this 
temperature to stabilize.


73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual




Floyd Sense wrote:



"Floyd Sense" <[EMAIL PROTECTED]> made an utterance to the drakelist 
gang

--

I have a set of temperature probes and will take some readings near the 
PTO with the fan blowing in and out to see what happens to the 
temperature. Hard to believe that mounting the fan to blow in, rather 
than out, would result in less PTO temperature rise.


73, Floyd - K8AC





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Re: [drakelist] TR7 fan recommendations

[Garey Barrell]

Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
This comes up every once in a while

The fan on the TR-7 should always be mounted to blow air OUT.   A piece
of electronic equipment that is DESIGNED to be fan cooled has a cooling
_SYSTEM_.The TR-7 system is designed for the air to be pulled in
through the slots in the top and bottom of the cabinet and blown OUT via
the fan.   Reversing this flow does not cool the entire transceiver as
effectively.   As for the PTO temperature, the absolute temperature is
not particularly important, rather the change in temperature as the
heatsink heats and cools with transmissions.  Blowing air IN forces the
heated air from the heatsink past the PTO area, causing the PTO
temperature to fluctuate.  The dial lamp that some cite as a source of
PTO drift is actually a constant heat source that helps to stabilize the
PTO area at a slightly higher temp.   There IS a "warmup" time for the
TR-7 for this temperature to stabilize.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual




Floyd Sense wrote:



"Floyd Sense" <[EMAIL PROTECTED]> made an utterance to the drakelist 
gang

--

I have a set of temperature probes and will take some readings near 
the PTO with the fan blowing in and out to see what happens to the 
temperature. Hard to believe that mounting the fan to blow in, rather 
than out, would result in less PTO temperature rise.


73, Floyd - K8AC



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Re: [drakelist] Certain R4B's may be factory wired for hum

[Garey Barrell]

Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
Denny -

Just one of the reasons PC boards are so popular!  :-)

Human beans make misteaks

I just happen to have an R-4B open on my desk working on the parts 
locator CD.  For reference for all of you who are rushing to check your 
R-4B...   The RED (plate) wire from the audio output transformer  
_should_  be connected to the SECOND tag from the chassis wall.  
Apparently Denny's was connected to the FIRST tag.   Hopefully this is 
an isolated incident, one of the assemblers being distracted 
momentarily!!   It would be interesting to hear if anyone else finds 
this error.


The resistor probably should be a 1W, this one is dissipating ~ 350 mW.  
It is snugged up against a terminal strip so has a little "heat 
sinking".   This receiver has quite a few hours on it, and the resistor 
reads 325 ohms, so must not be TOO overloaded.  It certainly would NOT 
be an easy replacement!


Doubling the size of the input capacitor DOES increase the load on the 
power transformer and rectifiers, especially at turn-on.  The only limit 
on the surge current is the transformer winding resistance.  I have no 
idea if, in this case, the increase in current is critical or even 
significant.  "Generally" it's not a good idea to increase the INPUT 
capacitor much over the design value for this reason.


Headphone hum is often a result of headphone sensitivity or frequency 
response.  Phones that are very sensitive can cause the user to operate 
the receiver with the AF gain control at a very low level, barely off 
the ON-OFF switch.  The causes a problem because the AF stages of the 
receiver run "wide open", and the volume is controlled by reducing the 
input signal level to the amplifier.  The result is that at very low 
volume settings the "signal to noise ratio" is poor since the "noise" is 
the same regardless of signal input level.  Hi-Fi phones are usually 
much more objectionable because of their extended low frequency 
response.   Communication grade phones normally have very little low 
frequency response.  The "fix" is to attenuate the AF output AFTER the 
audio stages by either a series resistor or resistive pad to reduce the 
sensitivity of the phones, allowing the AF Gain control to be set to the 
10-11 O'clock area for normal volume.


73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual




Dennis Monticelli wrote:

I thought I would share my recent experience involving replacing the 
power supply electrolytics in my R4B.




Denny  AE6C


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[drakelist] TR7 fan recommendations

[Floyd Sense]

"Floyd Sense" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
Thanks to all who responded with advice on fans to use for the TR7.  I 
located the Sprint SU2C1 that Garey said is the original FA-7 fan, and 
indeed it's listed as one of the most quiet (and with the lowest RPMs). 
However, I found a Toyo DC fan at Allelectronics.com for a fraction of the 
cost and only a couple of dB noisier if run at full voltage.  Here's a link 
to the fan if anyone else is interested: 
http://www.allelectronics.com/cgi-bin/category.cgi?category=220&item=CF-197&type=store. 
At only $3.75 brand new, it's worth a try, and will slow it down if the 
noise level is too high.


I have a set of temperature probes and will take some readings near the PTO 
with the fan blowing in and out to see what happens to the temperature. 
Hard to believe that mounting the fan to blow in, rather than out, would 
result in less PTO temperature rise.


73, Floyd - K8AC 


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RE: [drakelist] TR7 fan recommendation?

[Ron Wagner]

Ron Wagner <[EMAIL PROTECTED]> made an utterance to the drakelist gang
--
My guess is that Drake never figured you to run high duty cycle modes 
while mobile.  I would think a RTTY or Slow Scan setup a bit big for 
a mobile installation in the late 70s :-)  Then again what do I know.

73, Ron WD8SBB


I never understood the AC fan bit. A DC fan can easily be powered from
the radio, base or mobile. An AC fan is a doorknob if running mobile.
Maybe they were just a lot cheaper at the time.


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