Dead Peavey Classic 30

[benbeej]

I would appreciate any help on this amp.

The amp is not working and producing a loud hum while the power tubes are brightly lit when turned on. I have replaced all the pre-amp and power tubes with new ones based on an "expert's" advise and I am afraid I just fried them all as well because the same thing happened after it was turned on. Any thoughts on this?

I am also interested in installing a standby switch which would provide additional protection to the amp if anyone has any idea on how to do it.

Thanks,
Ben

[52 Bill]

Changing the tubes was not a bad idea, but obviously not your problem.

First off, by "brightly lit" do you mean small bright orange-yellow spots on each tube? Or do you mean large red-orange glowing metal plates in the power tubes? In either case, I doubt that you've damaged the new tubes by just turning it on.

Does changing any of the controls change the hum? Meaning, does varying the volume control make the hum louder or softer?

Give us a better description of the problem, and we can help make it go away.

[benbeej]

52 Bill, thanks for responding. The amp produced no sound at all when tried. I am not really sure if they are the metal plates as I immediately turned it off when I saw the unusual bright red-orange glow in the tubes, afraid that I could fry the expensive JJ tubes I just put in. I could try it again and post accurate description of the problem. The amp when initially turned on looked normal and I left it on for a couple of minutes and the lights in the tube grew progressively to large red-orange glow accompanied by loud hum. I'll try it again when I get home.

Thanks.

[52 Bill]

It sounds like it is doing what is referred to as "red plating". This is where the output tubes lose their bias voltage and overheat. The large metal plate in the center of the tube glows red-orange as the tubes start to self-destruct. Do not turn on the amp for any length of time or you will damage your new output tubes.

If you are experienced enough to troubleshoot the amp, start by testing the bias supply.
If not then get the amp to a qualified tech as this amp needs some circuit work to fix the problem.

[Enzo]

I would not expect red plates immediately once turned on, even with no bias at all. It takes a minute.

I'd suspect a loss of B+. Could be from a blown fuse - the fuses are in plain sight inside.

But loss of B+ can also come from an open resistor. Just fixed a C30 last night with an open resistor in the B+. Most common failure is that 390 ohm 5w between the first two nodes. Mine was the second resistor, a 10k. Of course on my repair the problem was the handle nut fell off into the works.