Crate GX-65 Loud noise

[TerryD]

I have my friend's amp here.  I'm not too familiar with solid state.  He complained of a loud HUM.  I could get it to do it once.  It is loud hum going into a buzz.  Any idea what that could be.  having a hard time getting it to do it again.  Grounding problem???  How do you trouble shoot this??  Thanks,Terry

[shooter]

How do you trouble shoot this?? 

schematic, name, brand?
sand isn't much different than tube Tshooting, voltage checks, physical inspection, isolating what works n what don't, but for help schematic is almost a must, pcb types, good pics of both sides maybe

[shooter]

name, brand?

sorry just read body NOT title
Doug has a GX120 schematic, from that I would monitor both the +/- 40 and +/- 15 for starters
work 1 channel at a time to see if it hummz,
some good "slapping around" with chop-stick might spook the intermittent, typically loose solder joint
I don't know age or service, but if it's 10ish years, ecaps.

you can probably stick a tone signal in and let it run, while beating on it, the gremlin Will eventually peek out.

[PRR]

Power supply hum/buzz usually won't stop.

Come-and-go hum/buzz suggests jacks. (Also cord plugs.....)

[TerryD]

Thanks all.  I'll get to it.  Terry