Peavey CS800 Blowing Fuse

[passaloutre]

I don't have much familiarity with solid state stuff, and if you've followed my posts around here you know I'm only starting to get the hang of the tube stuff. As fas as solid state, I've made plenty of fuzz pedals, but nothing remotely approaching this type of power.

I was gifted an ancient Peavey CS800 stereo power amp. Though I'm unlikely to ever need it's full rated power, I'm inclined to put it to use for sound reinforcement. I don't think it's completely fried, as it will pass small signals, e.g. I can plug a guitar straight into it, crank it up, and hear the guitar come out of the speaker, louder than I started.

But it pops the main fuse when I feed it a larger input, e.g. plugging that same guitar into a small mixer and plugging the mixer into the power amp. It doesn't pop until it gets a big transient, but when it does it dims the lights lol.

I haven't cracked it open, or even done anymore extensive testing than the above. I was hoping to get some old time wisdom before I do. What do I need to know before opening this thing up? Any caveats to 40 year old transistor devices that I should be aware of? The biggest things I've worked on are 70s era hundred-watt Fenders. I've attached the schematic below...what's a good plan of attack? Replace electrolytics, test transistors, look for anything burnt up? How do I test those big power transistors?

I have a scope, a signal generator, at least 2000W worth of dummy load, I could probably even get my hands on one of those cheap amazon transistor testers if I need to. What else do I need

[shooter]

What do I need to know before opening this thing up?

you have hair?  if so;
you'll have it all pulled out by the time you give up and place amp in recycle bin 


blowing mains is typically indictive of the PA section, the internet makes lots of "Blackbox" SS pa's
take the section i've copied, toss in trash, install the black box


i've T.S. many a SS circuit, this one is very complex, old, n broke, none of which is good for learn'n as you go.

[passaloutre]

haha I'm certain that is the best advice I will receive about this thing!

I did find a good long thread here that seems worth mining for some troubleshooting steps: https://www.diyaudio.com/community/threads/peavey-cs-800-issues.216627/

At least good enough to know if this thing only needs a quick fix or if it needs $200 worth of transistors