04-07-2016, 08:43 PM
>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.
Yup.
Sounds like it's in the amp. By grounding pin 3 you are shorting out all of the signal from the previous stages. Could have a bad 7C6 tube, heater to cathode short or one of the 41's. If you wanted to double check the p/s you could have a look at the dc outputs (B+ and - bias) with a scope to see if there is any ripple. Us old school guys can use a pair of hi z fones and a cap to listen for it.
Terry
Yup.
Sounds like it's in the amp. By grounding pin 3 you are shorting out all of the signal from the previous stages. Could have a bad 7C6 tube, heater to cathode short or one of the 41's. If you wanted to double check the p/s you could have a look at the dc outputs (B+ and - bias) with a scope to see if there is any ripple. Us old school guys can use a pair of hi z fones and a cap to listen for it.
Terry
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