04-07-2016, 06:55 PM
OK, Bob and Terry. I tried both of your suggestions.
Bob, I installed a new 20 uF/350V Â electrolytic in the spot where the previous tinkerer put in one-half of the dual cap. Powered it up and stepped thru AC inputs from 60V to 110V. Hum started around 80V and seemed just as loud as yesterday. So that doesn't appear to be a solution.
Next, I grounded pin 3 (grid) of the 7C6 per your suggestion Terry. The hum was still as loud as before. Removed the shorting wire.
Next I removed both 41 tubes. Ahhh, quiet throughout the land, with my input voltage variation of 60 - 110 V. Volume and bass/treble controls had no effect on the quiet. So it looks like the power supply is not the problem, correct?
Now I'lll start with the front-end 7G7 tube, and one-at-a-time, remove a tube and check for hum. Going down the line thru the 5 tubes before the dual 41's. Have I got that right? Thanks again for your suggestions.
And fifties, I have yet to hear any stations at any time.
Mike
Bob, I installed a new 20 uF/350V Â electrolytic in the spot where the previous tinkerer put in one-half of the dual cap. Powered it up and stepped thru AC inputs from 60V to 110V. Hum started around 80V and seemed just as loud as yesterday. So that doesn't appear to be a solution.
Next, I grounded pin 3 (grid) of the 7C6 per your suggestion Terry. The hum was still as loud as before. Removed the shorting wire.
Next I removed both 41 tubes. Ahhh, quiet throughout the land, with my input voltage variation of 60 - 110 V. Volume and bass/treble controls had no effect on the quiet. So it looks like the power supply is not the problem, correct?
Now I'lll start with the front-end 7G7 tube, and one-at-a-time, remove a tube and check for hum. Going down the line thru the 5 tubes before the dual 41's. Have I got that right? Thanks again for your suggestions.
And fifties, I have yet to hear any stations at any time.
Mike
