Pilot lamp falters.

[Sea Chief]

@g1 or Helmholtz

I seem to be back where I was with this a while ago. Specifically the hum -is- at the reverb, it seems. I mean I turn knob to 0 & no hum. Turn up & hum gets Louder. I pull tubes going along, then up to & only pulling v4 the hum stops.

So I know this as a juncture the area to focus on. And I tried 3 different 12ax7's, so the chances of all 3 being bad surely is ruled out.

(V5 had recent pro work done, a new socket, new tube too: if this info relevant).

Any help onwards form here.. would be great. (I have already: contact cleaned the 9 pins of v4, & contact cleaned the reverb phono plugs too. No change).

Thanks for reading again, SC

[Delta362]

You might be getting the tingle thru the screws of the knobs that are touching the pot shaft. Just sounds like you have a difference in ground potentials within your amp, your guitar, and your body.

As to the new hum from the reverb, since it was recently serviced, it could be a result of the reverb tank placement if it was removed during service and reinstalled in perhaps a different set of mounting holes. Unscrew the tank (or bag that's holding the tank) so that you can freely move the tank. Turn the reverb pot up to hear the hum, then slowly slide the tank all over the cabinet to see if you can find a location where the hum is the smallest.

[Sea Chief]

You might be getting the tingle thru the screws of the knobs that are touching the pot shaft. Just sounds like you have a difference in ground potentials within your amp, your guitar, and your body.

As to the new hum from the reverb, since it was recently serviced, it could be a result of the reverb tank placement if it was removed during service and reinstalled in perhaps a different set of mounting holes. Unscrew the tank (or bag that's holding the tank) so that you can freely move the tank. Turn the reverb pot up to hear the hum, then slowly slide the tank all over the cabinet to see if you can find a location where the hum is the smallest.

Hi Delta,

thanks for this. If the reverb hum suddenly stopped mid session, for 10 mins, then as abruptly started up again... this surely rules out the tank placement though? And it's always been in same two mount screws, & in a TR, well away from the amp too. Fine before where it is, should mean in my book, if it's not moved even a mm.. then it's same position cannot suddenly be the cause.

But I'm rarely right. i'm just falling back on common sense, as it were, although some will spit their tea reading -me- say this!

Thanks. I do have a new thread, if you can bear it, Reverb Humm Q. Really appreciate it if you could have a peruse. Thanks, SC