Tram D201A issues

[brownbomber72]

Picked up one recently that already has all caps and resistors replaced. All tubes test good. Here are the issues:

AM transmit: I can only get a 1 watt carrier at keyup with a swing to 10-15 watts. If I turn the transmitter tone control past halfway the key will jump up to 5 watts with no forward swing and a squealing sound will start coming from somewhere inside the radio.

SSB transmit: At keyup it shows almost a 15 watt carrier

Receive: It is off by one channel. Have to put it on channel 22 to be on 21 etc.

And for a recapped radio there is quite alot of hum coming from the speaker. What could be causing all these issues?

[2600]

Alignment is the starting point for performance issues. The carrier you see on SSB transmit is likely not anywhere near the selected channel frequency. Good chance that it's from the final stage oscillating. An inline frequency counter that shows what's coming out of the transmitter will most likely reveal that your SSB carrier is not anywhere near the selected channel frequency.

Typically this is caused by someone tweaking C706 for the highest wattmeter reading. C706 is not a "peaking" adjustment. It serves to cancel out the final tube's tendency to leak some of its output energy back into the final tube's input circuit. This will make it oscillate, not so different from the feedback "howl" you get by pointing a stage mike at the PA speakers. Only it's RF energy, not audio.

Unfortunately, the one part of the factory's alignment procedure that stinks is the one for setting C706. I'll guess that the adjustment screw in C706 is quite loose. Simply tightening it until you feel some real friction might stop the SSB carrier.

Just one problem. Any time you turn C706 it will change the peak setting of C711, the Plate Tune control, and the slug position of T700, the driver tube's output coil. Each of those will have to be peaked again, any time the setting of C706 is altered.

As for the hum, I have seen too many D201 radios that were "recapped" with only a fraction of the long list of electrolytic caps, usually the big ones replaced. The short 4-section 'can' C624 will cause hum issues if it's original. Likewise, there are a handful of other 8 or 10 uf 450-Volt caps that cause trouble if they are original. There are three electrolytic caps on the plug-in "BA" circuit board next to the 6L6GC audio power tube V603. If they are original, that could cause hum trouble.

The D201 has enough routine faults to qualify as a "barrel of monkeys" radio. Until you proceed to align it, when the phrase "herding cats" may come to mind.

Oh, and the one-channel wrong issue could be as simple as the set screw on the crystal channel dial.

73

[brownbomber72]

Thanks for the info. Where would I find C706?

[Trapper_267]

Here's what i ran into as far as the carrier on SSB with the mic gain at zero.
And Thank you Nomad for your encurging word's on the Neutralization and the by gosh, By golly method to adjust it.
I did manage to get USB to stop sending a carrier, But no luck on LSB. I could get LSB down to about 1/2 watt, But hardley any AM carrier,
I had gotten a BM board from Fixr and installed his BM board and the LSB carrier disapeared, Both BM board's had all the electrolithic cap's replaced and i never looked in to what was causing the BM board to have LSB carrier

I also installed Nomad's AA board noise kit and it is also fixed ((( Thank's Mr. Nomad))

Good luck Brownbomber72

[brownbomber72]

If some one could show me where all those adjustments are at I would greatly apreciate it

[Trapper_267]

Go here to CB Trick's Brownbomber72 and down load the service manual and schmatic.


cbtricks.org/radios/tram/d201a/