Another one with loud hum and no sound output...

[elkym]

I'm new here... and I've got a sort of spotty understanding of electronics...

It's a Peavey Audition Plus--

When I got it, the power tranny was hanging loose-- I had it checked out briefly by a guitar tech. He said that with the tranny hanging like that, it was probably bad, and that it wasn't worth fixing. Call me stubborn, but I hesitate to believe that a new tranny will cost more that the amp would... hell, you can get some basic Variacs for $25+.

I like Peaveys and I'd like to dink around with this sort of thing and learn a little bit. Where would you start? By the way, the line out doesn't seem to work, the power light does turn on, and I checked the speaker to see if it's DC current going to it-- it seems to be.

Any help?

[elkym]

K, update... Seems like it's the wiring coming from the transformer... I finally got sound after taking some screws out and moving things around a bit... but it's scratchy and spotty... Also, the transformer is getting hotter... is this normal?

[teemuk]

Nope.

Sounds like the output stage has blown. The transformer could be bad as well. But the only way to know for sure is to test those things.

[elkym]

how do I test the output stage?

Also, talked to another guy about it... described things... He says if I move the PC board or wires from the tranny around and I get a clear signal, then it's probably a broken connection on the PC board or one of those wires...

What generally happens if you remove the center tap, left leg, or right leg coming from the tranny? Would that create hum?

[Enzo]

The power amp is that 5-leg TDA2040 on the little heat sink off the rear edge of the board.  FLip the board over and resolder the legs.  WHile back there, resolder the large filter caps.  They are right behind the headphones jack.

Check the solder, and why not reflow it, on the jacks and controls along the panel.

If yuo think the transformer gets too hot, pull the red wires off the board and power up the chassis - that will be the transformer powered with the secondary connected to nothing, all by itself.  it will get a little warm, but if it gets real hot, that is not good.

[elkym]

I think I found the problem, and I don't think it was the transformer... it gets a little warmer than I might expect, but I started looking elsewhere for problems. Found that what gives me signal was something to do with the PC board. So I detached the pc board, and pulled it out... and found that if I put pressure on one corner of the board, I interrupt the signal, and playing with it, I believe I found that one problem was a part of the circuit path that was being grounded via a little mounting piece on each end. I insulated those spots, and now I get signal...

New problem... the clean channel sounds great, but the distortion channel simply sounds awful. Spotty and scratchy, although I never lose volume completely... have I burned up something in the distortion channel?