[Drakelist] T4X-C. Now more output power and no RFI?

[Chuck Pool]

Hi to all
My T4X-C always  put out about 110 -120 watts, less on 20 - 10 meters.  On 40 
meters there was always RFI problems with our organ.
 
Today, the T4X-C was putting out 150 watts on 80 meters.  All the other bands 
had much more output power too.  Amp meter said 400 - 450 mills.  320 - 350 
mills is normal for me.  400 - 450 amp mills seems to high?  Is it?
 
Now there is no RFI problem on 40 meters.
 
What is going on?  Any ideas?
 
73,
Chuck - AA5WG
Cedar, Michigan


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Re: [Drakelist] What circa tube tester?

[Garey Barrell]

Richard -

First, there are two major types of tube testers.  The least expensive 
is the "Emission" type which merely applies power to the filament and 
plate of a tube and measures the current on a "Good-?-Bad" meter scale.  
They are slightly better than using an ohmmeter on the filament pins to 
see if the filament is intact!  The more expensive type, the "Mutual 
Conductance" type, applies filament and plate voltage and then applies a 
known AC signal to the grid to measure the actual "gain" of the tube.


The Emission tester will tell you if the cathode is still emitting 
electrons, and the Mutual Conductance tester will tell you how the tube 
amplifies  _at the single test point and level_  chosen by the tester 
manufacturer.  Neither tells you much of anything about operation at RF.


Typically only the "latest" tube testers will test the "Compactron" type 
of tubes (6JB6) without some sort of adapter.


One of the better tube testers available is the military TV-7/U family.  
It doesn't have sockets to test the Compactrons, but someone has made a 
set of adapters for it to allow it to test the common sweep tubes, like 
the 6JB6.


All the rest of the tubes in the Drake gear are 7 and 9 pin "miniature" 
types, which just about any tester made after about 1940 will test.  
These tubes are all the same size pins and pin circle.


All that said, a tube tester isn't all that much help anyway.  The only 
REAL test for a tube is in the circuit you want it to work in.  Your 
best approach to maintaining your Drake gear is to get a couple of each 
tube type, "test" them by plugging into a working radio and if they 
work, put them in a safe place!


This is especially true for 6JB6 tubes used at RF frequencies.  These 
tubes were designed for use as horizontal output tubes for TV sets.  
They operated at almost 16 kHz in that service!!  Sylvania, in the early 
60's, characterized (tested) some of their "TV Sweep" tubes such as the 
6JB6 for linear amplifier service from 2-30 MHz.  The resulting data was 
used by Drake and several other Amateur equipment makers to develop 
transmitters that would run considerably more power than those using the 
6146, and do it at a lower plate voltage!  Add that the sweep tubes were 
about 1/3 to 1/2 the cost of the 6146, and that a lower plate voltage 
could be used for higher power output and it was a done deal.  The 
pertinent characteristic was a high "perveance", or high currents at 
lower plate voltages.  They were designed to operate 24/7, inside a TV 
set with 25 other tubes and keep working, so they were able to serve in 
CW or SSB service at considerably higher power levels than their 
published specifications..


The catch here is that since the tube was designed to operate at 16 kHz, 
NOT 30 MHz, not all brands of the same tube type were interchangeable.  
Operation at 30 MHz requires considerably more attention to internal 
tube structure such as lead lengths, interelement capacitance, etc.  The 
result was that one manufacturer might make a 6JB6 with considerably 
higher reactances that worked just fine at 16 kHz, but would make it 
impossible to neutralize in an HF transmitter without changes in the 
neutralization circuitry.  Add the fact the some of the smaller, even 
well known companies that put their name on a tube may well have had 
that tube made by more than one manufacturer, and it gets difficult to 
say which tubes will work in a T-4X and those that won't.


Further complicating the situation is that the RF gain of a tube falls 
off with decreasing emission, and falls off first at the higher 
frequencies.  6JB6 tubes in T-4X service will fall off first on 10M, 
then 15, then 20, then ...   Most will continue to put out SOME power on 
80 and 40M after 10M output is just about zero.


My experience has shown that Sylvania, Zenith, RCA and GE are the ONLY 
brands of 6JB6 that I have found to work  _consistently_.  Raytheon, 
Westinghouse, Standard, and most others are potential trouble.  Some 
work, some don't, depending upon who  _really_  made them.


By the way, it is NOT a good idea to replace ALL the tubes in a radio at 
once.  "Retubing" is somehow seen as similar to "replacing all your 
tires".  This is not only wasteful of a finite source of vacuum tubes, 
but can turn a working radio into one that doesn't!  Even New Old Stock 
tubes, all manufactured over 30 years ago, are not all "good".


So get a few spares for each type,  _check them in a currently working 
radio_, and if they are "good" put them in your tube stash for a rainy day.


73, Garey - K4OAH
Glen Allen, VA

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



Richard Palmer wrote:
I hope this is not off topic.  With the use of "vintage" being used 
for all Drakes and tube testers, many from the 1940's and before, up 
to the last ones made, it has become impossible for me to determine 
what will service my early TR-4.


I have spent hours and hours looking up tube testers by

[Drakelist] What circa tube tester?

[Richard Palmer]

I hope this is not off topic.  With the use of "vintage" being used for 
all Drakes and tube testers, many from the 1940's and before, up to the 
last ones made, it has become impossible for me to determine what will 
service my early TR-4.


I have spent hours and hours looking up tube testers by type, make and 
model. I have spent hours squinting at pictures trying to count socket 
pins. I am burnt out and am looking for help in finding just where to 
look. I have no idea if post WWII testers even test 9 pins, or if all 7 
pins are of the same size.


Richard Palmer
KB8NXO

--
The law, in its majestic equality, forbids the rich as well as the poor to 
sleep under bridges, to beg in the streets, and to steal bread.   - Anatole 
France


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Re: [Drakelist] TR7 acting strange

[Garey Barrell]

Hi Gary -

Ron's unit was locking ok except on the top of 10M..  The regulator 
is specified +/- 1V  (+/- 4%) so from what you say, a changed regulator 
might be in order.  The "A" version is +/- 2%.


Your message does bring up a question that I have been pursuing.  You 
mention the wire loop around the transformer as holding the core 
sections together.  It doesn't!  :-)   The wire loop is wrapped around 
the lower core half, 90 degrees from where it would be to hold the 
sections together.  The wire is also stripped and soldered together, 
forming a shorted turn.  I "think" its purpose is to shunt the external 
field from the transformer, much like the copper band around many power 
transformers.


The other thing that Ron is seeing is that the unregulated 30V is 
considerably lower (~27V) for the first 10 seconds after turn-on, when 
it jumps up to 32+.  I was wondering if the multivibrator was slow to 
start, and your mention of the added resistors and/or caps is interesting.


For the R-7 they gave up entirely, and used a single transistor 
oscillator driving a power Audio Amp chip.!   Lots simpler


73, Garey - K4OAH
Glen Allen, VA

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



Gary Poland wrote:

Ron,
  I haven't been following the thread but of the TR-7's that I have 
owned or serviced the lowest I have seen the +24 volts and not had an 
issue with the PLL locking up on 14 mhz and higher was 23.6 volts. 
That's not to say 23.3 vdc is bad, I just haven't yet seen it. The 
voltage just needs to be high enough for the VCO to work on higher 
frequencies.
  The 30 vdc input for the 24 v regulator is derived from the DC 
inverter Q2104, Q2105, T2101, and associated parts. Some times the 
powdered core halves of T2101 will separate and lower the 30 volts 
input. In that case just reposition them and tighten the loop wire 
holding them or use hot glue to keep them in place. Some power supply 
boards will have 68 ohm resistors soldered across R2129 and R2130. 
This may also help to raise the 30 volts from the regulator. I also in 
one case I replaced C2117 and C2115 with .033 ufd to get the voltage 
up. Like the 68 ohm resistors some boards have those same capacitors 
soldered on the backs of the board so I suspect Drake had issues with 
the design.

73, Gary W8PU
http://home.roadrunner.com/~w8pu 



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Re: [Drakelist] TR7 acting strange

[Mike]

Gary,

great shots of the Drake stations across the years;  I had a ball with the 
TR-33C; I purchased one when they first came out and had it crystalled for the 
one local  repeater and 146.52.  I still have it here and put it in service on 
the outside antenna occasionally and receive great audio reports!  (slightly 
off topic)

73 de W4DLMike
Pompano Beach, FL USA


  - Original Message - 
  From: Gary Poland 
  To: Drakelist@zerobeat.net 
  Sent: Saturday, January 30, 2010 2:05 PM
  Subject: Re: [Drakelist] TR7 acting strange


  Ron,
I haven't been following the thread but of the TR-7's that I have owned or 
serviced the lowest I have seen the +24 volts and not had an issue with the PLL 
locking up on 14 mhz and higher was 23.6 volts. That's not to say 23.3 vdc is 
bad, I just haven't yet seen it. The voltage just needs to be high enough for 
the VCO to work on higher frequencies.
The 30 vdc input for the 24 v regulator is derived from the DC inverter 
Q2104, Q2105, T2101, and associated parts. Some times the powdered core halves 
of T2101 will separate and lower the 30 volts input. In that case just 
reposition them and tighten the loop wire holding them or use hot glue to keep 
them in place. Some power supply boards will have 68 ohm resistors soldered 
across R2129 and R2130. This may also help to raise the 30 volts from the 
regulator. I also in one case I replaced C2117 and C2115 with .033 ufd to get 
the voltage up. Like the 68 ohm resistors some boards have those same 
capacitors soldered on the backs of the board so I suspect Drake had issues 
with the design.

  73, Gary W8PU
  http://home.roadrunner.com/~w8pu




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Re: [Drakelist] TR7 acting strange

[Gary Poland]

Ron,
  I haven't been following the thread but of the TR-7's that I have owned or 
serviced the lowest I have seen the +24 volts and not had an issue with the PLL 
locking up on 14 mhz and higher was 23.6 volts. That's not to say 23.3 vdc is 
bad, I just haven't yet seen it. The voltage just needs to be high enough for 
the VCO to work on higher frequencies.
  The 30 vdc input for the 24 v regulator is derived from the DC inverter 
Q2104, Q2105, T2101, and associated parts. Some times the powdered core halves 
of T2101 will separate and lower the 30 volts input. In that case just 
reposition them and tighten the loop wire holding them or use hot glue to keep 
them in place. Some power supply boards will have 68 ohm resistors soldered 
across R2129 and R2130. This may also help to raise the 30 volts from the 
regulator. I also in one case I replaced C2117 and C2115 with .033 ufd to get 
the voltage up. Like the 68 ohm resistors some boards have those same 
capacitors soldered on the backs of the board so I suspect Drake had issues 
with the design.

73, Gary W8PU
http://home.roadrunner.com/~w8pu

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Re: [Drakelist] TR7 acting strange

[Ron]

Garey,
Even thought I had spontaneous healing of my TR7 per our e-mail discussion, I 
opened up the rig and did some voltage tests.  Rig in SSB, all boards installed.

Pin  spec   measured 
1   -5V -3.43
2   +25 23.3
3   gnd
4   AM  4.99
5   RTTY7.01
6   CW  4.31
7   LSB 6.26
8   USB 3.83
9   DCin13.53
10  +10VDC  10.01
11  +5V 4.90

The 24VDC line stayed solid as I moved the bandswitch and up down buttons.

Per the drake service dept alignment procedures, pin 2 should measure between 
23.25-24.0.  Assuming my meter is accurate, that voltage is very close to being 
out of spec low.  Maybe a weak/leaky C2110? 

I could not get to the input of U2103 (24V regulator) without pulling the DR7 
board.  Pulled it and installed probes and then reinstalled the DR7.  Input to 
the 78c24 was at 27VDC immediately after turning on the rig, and then climbed 
to 32-35 volts w/i about 10 seconds.  As I recall the 7800 family of chips need 
2 volts to regulate, so I think input is w/i spec even at turn on.  When 
switching the bandswitch, it made the input voltage move, but never under the 
32 volt level.  Caveat, using a DVM so it may have "spikes" that I was not 
seeing.

After this, I pulled the DR7 and replaced it with the service kit "jumper logic 
board".  Basically had the same results with it in place of the DR7 board. 

TNX es 73,
Ron

--- On Mon, 1/25/10, Garey Barrell  wrote:

> From: Garey Barrell 
> Subject: Re: [Drakelist] TR7 acting strange
> To: "Ron" 
> Date: Monday, January 25, 2010, 9:56 AM
> Ron -
> 
> Definitely sounds like marginal VCO locking.
> 
> The bands from 160 - 20M will all wander around 17
> MHz.  15 and 10M 
> bands will wander around 34 MHz.
> 
> An "open" AUX-7 position will result in an unlocked VCO, as
> will pushing 
> the FIXED RCV button in.
> 
> First step is to check that +24V DC supply bus.  That
> is the most likely 
> cause of this, i.e., "random, occasional, loss of lock" on
> both PTOs.  
> Certainly there are other possible causes, but that little
> transformer 
> core is a problem, and the "super glue" that Drake used to
> put it 
> together is letting go (after only 40 years or so). 
> Easy fix, just glue 
> it back on.
> 
> 73, Garey - K4OAH
> Glen Allen, VA
> 
> Drake 2-B, 4-B, C-Line&  TR-4/C Service Supplement
> CDs
> 
> 
> 
> Ron wrote:
> > Garey,
> > I started to look at the TR7 last night.  First
> was to see for sure what was going on frequency wise. 
> Turned it on, 80 meters, where I had left it and it was
> fine.  2.5 then 1.5 wondering 17xxx.x 1.5.  Back
> to 80 meters fine, and of course everything else was fine
> too.  So then I went back down to 2.5 and 1.5, they too
> were fine now.  So I thought maybe temperature or time.
> Could not get it to fail after several hours.
> >
> > Got to playing and went to aux settings.  They
> were fine with the band light lighting if I was not in the
> correct band.  Then I went to an open aux location and
> got wondering 17xxx.x.  I can not remember it that has
> always been that way or not.  Looks like it could be
> correct given the "block" diagram of the rig in my head.
> >
> > So I know it sounds like VCO/PLL issues, which
> voltages are most likely.  But, is there anything in
> the bandswitch that exercise might cause to "clean
> up"?  Or am I in for what looks to be a PITA
> intermittent?
> >
> > Also, I have looked for how my TX is open.  The
> motherboard out of lock trace is not cut, and the Q9001
> collector on the DR7 board seems in tack. Maybe I just
> missed how they defeated Q9001.  Is there something
> with the aux board that also somehow "opened" the TX? I
> thought it was only for the modules in aux, not the whole
> TX?
> >
> > Thanks in advance. Also thanks for being an anchor for
> this list. Your knowledge and willingness to share that
> knowledge is a tribute to the real meaning of Ham Radio.
> >
> > 73,
> > Ron WD8SBB
> >
> > --- On Sun, 1/24/10, Garey Barrell 
> wrote:
> >
> >    
> >> From: Garey Barrell
> >> Subject: Re: [Drakelist] TR7 acting strange
> >> To: "Ron"
> >> Cc: Drakelist@zerobeat.net
> >> Date: Sunday, January 24, 2010, 4:40 PM
> >> Ron -
> >>
> >> You may need to recheck your frequencies. 
> ~17 MHz is
> >> the "target" frequency for the Lo Band VCO
> (through 20M),
> >> and 34 MHz for 15 and 10.  This is where the
> VCO's
> >> settle when unlocked.
> >>
> >> First thing to check is the +24V DC supply. 
> This
> >> higher voltage is used for the Loop Filter and
> VCO
> >> steering.  If the voltage is low, check that
> "E" core
> >> on the DC/DC converter transformer on the little
> power
> >> supply board.
> >>
> >> There are other possibilities, but this is a
> start.
> >> Unless the transmitter has been modified, it won't
> transmit
> >> if the VCO is unlocked.
> >>
> >> 73, Garey - K4OAH
> >> Glen Allen, VA
> >>
> >> Drake 2-B, 4-B,
> C-Line&   TR-4/C Service Supplement
> >> CDs
> >> 
> >>
> >>
> >> Ron wrote:
> >>      
> >>> Got a strange one go