[tbone]

Here is a link to the whole schematic which includes the tuning info and voltages.

6S254 W Tuning Info

When I read the last post, it was stated that the generator was connected to the A terminal with a .5uf cap. That does not jive with the instructions. The only time a .5uf cap is used is for the IF alignment, and that is at the grid of the 6A8. The rest of the time either a 200pf cap or 400 ohm resistor is used at the A terminal. Regardless, that is not the root cause of the issue.

I also noticed that the voltage listed at the 6A8 and 6K7 grids is listed as -0.5 volts, not -2.6 volts. However, the first plate of the 6H6, the source of AVC voltage shows -2.5 volts. The -.5 volts could be a schematic error? My guess is that the -2.6 volts you are seeing is a symptom and not a problem. It simply means the 6H6 detector is not getting a strong enough signal to create more negative AVC. I suspect this voltage is the quiescent state no signal voltage.

Isolating which RF stage that’s going bad, RF or IF, would be my suggestion. You could run the radio with a modulated IF signal injected at the 6A8 grid per the alignment instructions, then wait and see if the radio quits. It is possible that the 6H6 tube could be an issue. They are known finicky tubes.

It was mentioned that there is a Bluetooth device somehow connected to the audio section. It is possible it could cause an issue. There are many components after R7 and C10 that could have a loading effect. I think it was mentioned before to disconnect additional components with this circuit. I know it’s a long shot, but still worth mentioning.

Obviously this is not a simple problem, but breaking the radio down section by section, would be how I’d tackle this problem. Usually one works backwards from the audio section, then the IF, followed by the RF section. I suggested the IF stage because we are confident the audio is good.

Just some more thoughts and suggestions. Maybe someone else can chime in with more ideas.