I recently bought a Harman Kardon HK870 amp from a guy. It worked fine for a minute or two at moderate power level, then blew fuses & quit. Replaced the two fuses on one channel of the power supply (right off the transformer, before the bridge). The new fuses went out immediately, heard lots of 60 hz from the speakers for about half a second before they blew.
It's possible this amp had not been used for awhile. I'm thinking about the capacitors having been sitting without use for awhile . . . would they tend to short out due to lack of use??
Thanks, Scott Kelley