Hello,

I have a DSL15 that is humming a 120 Hz tone, even with all controls down. This tells me the trouble is in the power section. I checked the bias voltage of both 6V6 tubes, and they are there. However, when I checked the voltage across the plate current sensing resistors, one is around 24 mV, and the other is virtually zero. I swapped the tubes, and the voltage values on the resistors went the other way round. It looks I have a bad 6V6 tube, but I'dlike to confirm before I go buying a new one. Any thoughts?

Thanks!

My J60 tube amp made a loud POP while jamming. All the tubes are secure and lit up, and the fuse still looks good. The amp isn’t making any sound at all though. Any suggestions on what might be the problem?

I've got a Valvestate S80 8240 which has developed a loud hum whether instrument plugged or not.

The hum disappears when it is tilted forward. Can anyone suggest a home fix?

I put up this question before but for some reason it seems to have been deleted!