Help with Peavey Classic 30 please

[Jim Goad]

Got this recently knowing it had issues. Speaker, caps and preamp valves have all been replaced but I’m now getting the issues in the YouTube vid. Crackling and loud screeching that kicks in as the amp warms up and settles down after a while. Tapping the output valve closest to the preamp valves makes it happen again. Every knob is turned down btw.
Do I just need to get new valves or is there anything else that might be causing this?

[Dr Tony Balls]

It could be the valves, or could be a bad solder joint somewhere. Try pulling each preamp valve and seeing what happens with any of them missing. If that doesnt solve anything, then move on to the power valves. Pull the outer two valves and see if that changes anything. If it doesnt put them back in and pull the inner two valves and try. The main point here is you're trying to figure out what tube/socket combo (if any) is causing the problem. Once you figure that out then you can label that tube and try it in a different socket to see if the problem follows the tube or the socket.

[daCod]

ugh, classic peavey

[Dr Tony Balls]

This is the sort of thing that I would *love* gutting and rebuilding as an AC30-ish amp with proper mounted components. That's not for everyone though.

[Jim Goad]

Thanks Tony. I’ll give all that a try.
It’s a decent sounding amp, good reverb, fx loop and a boost switch. I prefer Peavey’s build quality on solid state stuff though. This thing is turning into a money pit.

[5E3]

Have you tried another set of power tubes to rule that out?

Maybe some excess solder dripped into the sockets interfering with contact between some pin and socket?

edit: nm the sockets are PCB mounted. I would check the board (drain the filter caps first!)

[Jim Goad]

Thanks for the help everyone. A thorough check of all connections and a bit of testing led to the conclusion that a power valve was the issue. Price of valves is crazy high right now and the value of U.K. Sterling plummeting hasn’t helped so it took a while to find some at a good price.
Amp is all sorted and it’s a decent sounding combo. I’ll probably end up selling it as I’ve had to plough a lot of money in but I’ll enjoy playing it for a while first.

[pothole]

My old Classic 30 exhibits this behavior every now and then as well and it's always a power tube. It runs those EL84's pretty hard it seems. I keep a box of extra tubes in the amp for that reason.