[Drake] [Drakelist] TR4C weird xmit trouble

[Dick KF4NS]

RESENDING THIS DUE TO WRONG ORIGINATOR ADDRESS (STUPID ME!)

Garey,
This is not new to me. I acquired it in 1995 after it had been stored
in a garage for 10 years. No need to tell the tale, you can just
imagine. After a physical cleaning I fired it up and it worked fine.
Then this year I decided after getting  your CD that it was time to do
a real restore which I did. I will never say that was a bad idea since
it was not even close to good performance.

20 meters had been working at par for the rest of the bands. The
finals are what was in there, Sylvania 6JB6 da ALM marked on them. As
tested on my B&K 707, the gm was for V8=9000 V9=9500 V10=10500, for
what it is worth.
Neutralization went well using my scope with voltages removed from
finals. Will do it over but tune up on 28.0 instead of 29.1 just for a
do-over again.

By the way, the schematic you recommended was series 35161 but I
discovered yesterday that mine is a match for series 42500 even though
mine was built in '74 with serial #38145, go figure. It has those
goofy brn/blk/wht/silver bypass caps across IF xfmrs T11/T12. Took
quite a while to figure out they were caps and not resistors. Never
ever saw those things before.
73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!

----- Original Message ----- 
> Message: 1
> Date: Tue, 12 Oct 2010 14:27:29 -0400
> From: Garey Barrell <k4oah at mindspring.com>
> To: drakelist <Drakelist at zerobeat.net>
> Subject: Re: [Drakelist] [Drake] TR4C weird xmit trouble
> Message-ID: <4CB4A891.1080803 at mindspring.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Dick -
>
> Is this a 'new' transceiver to you?  Has it ever worked on 20M to
> your
> knowledge?  20M is one of the 'simple' bands, (the other one is
> 80M,)
> where Q1, Q2, V1 and V3a are not used at all.
>
> What brand are the final tubes?  Are they the same brand?
>
> It sounds like the PA is oscillating.  The most common cause is
> off-brand or mis-matched final tubes.  Next is improper
> neutralization.
> Next would be a bad bypass cap.  There is also a possibility with
> the
> TR-4 series of mistuned bandpass transformers. You could remove the
> PA
> tubes, or just remove the screen voltage at the third feedthrough
> from
> the back on the PA shield under the chassis (C75).  Careful, the
> second
> one from the back is the HV!  Once the PA is disabled, see if you
> have a
> correct 20M signal out of the Driver stage (V6).
>
> I suspect if you checked your '20M output', you'd find that it's NOT
> where you think it is.  Does the output peak with the RF TUNE
> control in
> approximately the correct place?  IF you listen on a separate
> receiver,
> is there a signal where the transceiver dial says it is?
>
> 73, Garey - K4OAH
> Glen Allen, VA
>
> Drake 2-B, 2-C/2-NT, 4-B, C-Line&
> TR-4/C Service Supplement CDs
> <www.k4oah.com>
>
>
> Dick KF4NS wrote:
>> I sure hope I am not making a nuisance of myself but I am out of
>> ideas
>> and have tried everything that was suggested, including
>> neutralization
>> (which was ok) and have read the manuals for service and owners
>> over
>> and over for hours, and have studied the schematic for hours and
>> hours.
>>
>> The original message was for a trouble just trying to set the bias
>> which was fine on all bands but 20M. Since then, I have tried to
>> tune
>> up in the X-CW position and all bands tuned fine except for 20M.
>> On 20M I can get a power out of 150W but the plate current is
>> 600ma,
>> the xmit gain dips the plate current (yes, the xmit gain!), the
>> plate
>> tune cap also dips the current but output drops to nothing, the RF
>> tune acts like the xmit gain should.
>>
>> The only real defect I did find was R53 1.5K in the plate circuit
>> of
>> V11 was cooked. I replaced it.
>>
>> This rig has been gone completely refurbished recently with bad
>> tubes
>> replaced, all contacts cleaned and contact enhancer applied, 9mhz
>> osc.
>> set right on, 100khz osc set right on. neutralization set on 10M,
>> resoldered the contacts on the rear wafer of bandswitch, C145
>> replaced, P.S. upgraded to AC4R.
>>
>> Keep in mind, ALL BANDS RECEIVE FINE AND TRANSMIT FINE except 20M.
>>
>> Please help, Thanks and 73, Dick KF4NS
>> St Petersburg, FL 33714 USA
>> Keep The Glow!
>>