Hiwatt 20 amp

hiwatt 20 tube amp has a hum problem, any advice?

electrolytic capacitors dry out with time and may cause hum.

Ron likely nailed it. Someone was nice enough to make some of the schematics of some of the amps available. See: **broken link removed**

www.tubesandmore.com may be a good source of parts especially the can-type muti-capacitor capacitors. Some people for esoteric reasons may stuff the cans with modern caps and/or use the modern caps where they don't show, but leave the bads ones for show only.

If it happened after an attempted repair, check that the power transformer was not rotated 90° by accident. The poorly oriented magnetic field of the power transformer can bring humm-havoc to the rest of the unit.

also, hum can caused by a heater-cathode short.