Late 70s kustom ii amp

[juptonstone123]

I just picked this up. It has a slight hum on one channel.and a bad one on the other. I'm almost positive it's a ground loop issue. Does anyone have a schematic?

[The Dude]

Many of the Kustom schematics are by circuit board instead of model number. Check your circuit board numbers against those on this page (link below). If that doesn't help, please list the numbers on your boards, and someone here may have them.

http://www.vintagekustom.com/literat...h/AmpList.html

[Chuck H]

That's where I found my schematics when I needed to repair one of those amps. Great resource. Most of the Kustom amps were "modular" in that they were comprised of a combination of available circuit boards and the boards are individually assigned as units. So you can't really look up an amp schematic as well as you can look up the PCB schematics on this site.

And I seriously doubt the hum is a ground loop. Even though it may sound like one. These amps didn't hum from the factory and they aren't commonly modded or friendly to the effort. So a ground loop would have come from the factory. Which it didn't so it's probably not a ground loop.

More likely one or more of your output transistors is failing and putting DC on the speaker. Which is very bad for the speaker so you should check for this and then never turn the amp on into a speaker again before it's repaired.

[Jazz P Bass]

I agree with defining the board #'s.
There is a Kustom II bass, guitar & a PA amp.