Metropoulos Forum

I built my 69 Super Lead clone 4 years ago, or so. I played through it for two years with no issues and then, because of a move, I had to put the amp in storage for a couple of years.

With no guitar plugged into the amp, it buzzes loudly once I turn the volume up to 2 or higher. I exercised all the pots, jacks, and swapped out all the tubes. No improvement. I know the outlet is well grounded, and all of my other amps are dead quiet on the same circuit and in the same location in the house.

Bad cap? Something else?

check filter caps

Roe is there an easy way to check the caps without replacing them?

easiest would be just to place a new cap in parallel to the old one. however, before you do this check the wiring of the caps and whether they look good

Check your tube sockets, maybe they have oxidized preventing good contact with the tube pins.

If the amp does no buzz with the volumes down it´s not a problem with the filter caps. I would check the input jacks. Maybe they do not switch ground properly with nothing plugged. This does a nice absolutely damaged sounding noise when turning up the volumes.
Its a common problem with the Cliff-style jacks that the switch contacts do not work properly when they are not touched over a longer time.
Maybe you can check them with a shorted plug and identify the faulty one.

That's not necessarily true. If the filter cap on the input stage is kaput, you could get that. That could happen if, for example, the amp is turned out without it on standby after sitting around for a long time. The combination of the cap deforming and getting hit with the full B+ until the preamp tubes' cathodes warm up could push any cap over the edge. I would try hooking a second cap across the filter caps. It may not even be the input filters that are bad. If they are all weakened, the input stage is going to be the most susceptible to low levels of hum.