Question about hum from speakers


I know there's at least one amp engineer here... I'd like some help.  I bought a used solid-state amp from ebay; the ad read " McCORMACK POWER DRIVE DNA-.5 Deluxe REV B POWER AMPLIFIER - EXCELLENT CONDITION!"
Well, I swapped it in, replacing a Dynaco Stereo 120, and there's a hum from both speakers.  I have to believe that the seller was well aware of the hum.  What I'm wondering is, is the hum a result of some electronic component(s) in the amp failing (or having failed), such that it's salvageable by replacing the bad component(s)?  Or would that be hoping too much?
bhakti-rider

Showing 2 responses by jetter

Try unplugging components until you isolate the component causing the hum.  Also note, that I have had RCAs on my turntable that were not insulated enough and these caused hum, which when replaced, went away.
My ground loop was caused because I have my stereo also hooked up to the tv cable box for watching some tv shows.  Buying the following isolator completely eliminated the hum.
Jensen VRD-1FF IsoMax Digital RF Isolator

https://www.parts-express.com/jensen-iso-max-vrd-1ff-75-ohm-inline-digital-catv-isolator-hum-elimina...