#1
hello , I play through an old peavey PA head, the peavey standard mixer to be exact.

heres a picture and the manual -

http://www.peavey.com/assets/literature/manuals/80361027.pdf


the other nite while I was jamming the amp shut off and I checked the fuse and sure enough it was burnt and no longer connected. I went to radio shack and bought a pack of fuses identical to the broken one ( AGC 5 volt fuses 250 watts)

when i replaced the broken fuse, the amp burnt through the new one in a few seconds, and again with a 3rd, and thats when I stopped and came here to write this post!

any idea why my head is burning these fuses? any ideas or general information is greatly apprciated. thanks

-mark
#2
Although I couldn't pin-point the problem without physically taking a look, as you would know the fuse is blowing due to too much current flowing through it, as it is designed to do.

In this case it would probably mean the electronics have 'broken' somewhere along the line causing this abnormaly large flow of current. My best suggestion is taking it to a guitar shop where they can repair amps and get them to take a closer look, most places will give you a free diagnosis.

Also, I'm not 100% sure on this but should the PA mixer be used as an amp head, I feel that could be the problem. Have you been using it for this purpose before w/o any problems?
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#3
it means something else is broken.

or your fuse holder is broken.

hmm?
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#8
Ok, and you say it's frying fuses every time. My best bet would be that a transistor blew, because a tube amp does the same thing when the power tubes go, and transistors act just like power tubes do.

What I'm going to ask you to do is to open up the amp and take out the board, if mine(AudioChoice QM4 PA mixer) is anything like yours, it should like kinda similar, but just loosen the screws on the top and bottom, mine had 6 screws, and it should just slide out from the case fairly easily.

Now your transistors look similar to chips, except they stand straight up and have three large prongs, and are usually attached to a heat sink of sorts. Here's a picture of mine, it's those black chips attached to the side of that large silver heat sink.



Check all of those and look for any burning, there are ways to test them, but idk how. They are usually fairly easy to replace and are relatively cheap.
#9
First thing you do is pull it apart and clean it. Get a can of compressed air if you don't have a compressor. You'd be amazed how many things a good clean fixes.
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#10
ethan ive located the 3 transistors in the head, they do look a little tarnished (though not sure if this is actual burning) but how would i determine which transistors to replace them with?

on the 3 transistors they read from left to right " EP430 A7611" "EP431 A7634" and finally "EP430 A7601"

i know they carry transistors at radioshack, would they have ones that would work for this?

-mark
#11
Quote by marknebraska
ethan ive located the 3 transistors in the head, they do look a little tarnished (though not sure if this is actual burning) but how would i determine which transistors to replace them with?

on the 3 transistors they read from left to right " EP430 A7611" "EP431 A7634" and finally "EP430 A7601"

i know they carry transistors at radioshack, would they have ones that would work for this?

-mark


I'd go ahead and replace them anyways, just cause they do wear out over time, couldn't hurt. Idk about the radio shack ones, but as long as the model number matches exactly, brand is not an issue, it's just those numbers have to match. Just make sure you put the right one back in the right spot, which I'd remove them one by one and replace them one at a time so you don't get them mixed up.

Another thing is to be careful not to get them too hot when soldering, they can burn up.

In order to find the right one, since it's an old amp, you might have to do some research to make sure that the new part numbers correspond to the correct transistor.

Hope this helps you out some.