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Tram D201 ssb hum in receive
- Thread starter klj2497
- Start date
klj2497,
Just a few quick observations-If you have "been there, done that" please ignore.
If hum is in SSB RX only, I would look strictly at the SSB/RX signal path. Perhaps a diode or tube active in SSB only?
I would assume (never been inside a D201) that power supply rectifiers are the same circuit in AM as well as SSB but if not, a bad rectifier diode in the power supply?
Noise blanker circuit/tube?
If the hum can be "squelched out" it suggests that the noise/hum is in the IF strip of the SSB RX? Could be a weak or "noisy" tube??
Good Luck. I'm a sucker for the old classics!
73
David
Just a few quick observations-If you have "been there, done that" please ignore.
If hum is in SSB RX only, I would look strictly at the SSB/RX signal path. Perhaps a diode or tube active in SSB only?
I would assume (never been inside a D201) that power supply rectifiers are the same circuit in AM as well as SSB but if not, a bad rectifier diode in the power supply?
Noise blanker circuit/tube?
If the hum can be "squelched out" it suggests that the noise/hum is in the IF strip of the SSB RX? Could be a weak or "noisy" tube??
Good Luck. I'm a sucker for the old classics!
73
David
This is a long shot, but try tapping on the tubes (with something plastic) while the Tram is ON to see if it changes. I had one (long time ago) and did the tap-tap-tap procedure and found the culprit tube (I thought).... LSS - it was the tube socket.
I found it! tube v502, I have some extra tubes from replacing them all so i swapped out one at a time starting with v500 and found it was a bad 6gh8a.