[Drake] TR4C weird xmit trouble

[Dick KF4NS]

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!

----- Original Message ----- 
From: "Dick KF4NS" <kf4nsradio at verizon.net>
To: "DrakeRadio list" <DrakeRadio at yahoogroups.com>; 
<drake at mailman.qth.net>
Sent: Monday, October 04, 2010 6:09 PM
Subject: TR4C weird xmit trouble


> Ok guys, I have this black cloud over me right now. The radio is
> receiving fine (other than the filter defect) and I decided to get 
> the
> xmit completely checked out before I wrap it up.
>
> All of a sudden while on 20M band position and checking the PS bias,
> it jumps intermittently to 400-600ma with no drive, sideband switch 
> in
> ccw position (actually  makes no difference), dummy load connected 
> and
> no mic or key connected.
>
> After quite a few hours pulling out my hair (just the gray ones) I
> tweaked the TUNE control and the trouble went away. I tried full ccw
> and cw and everything  in-between on all the other bands and no
> effect, only affects 20M and only when the TUNE control is between 1
> and 6. I checked and rechecked the band switch contacts over and 
> over.
> What the heck, I even tapped all the tubes and every other silly
> thing. Given time and a few cups of coffee I can usually make sense 
> of
> these kind of things but not this time. HELLLLLP!!
>
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
>