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Discussion Starter · #1 ·
The story:

I have a used Peavy Classic 50/50 power amp. When I purchased it years ago, channel 1 didn't work, but channel 2 did (as well as one of the LEDs for one of the standby switches).

I later took it to what I thought was a reputable shop in Portland (whose name I'll leave out). They had the amp for, I think, about 3 months along with a diagnostic/deposit fee of $200. After which they told me that it needed new tubes and wanted to charge me another $200 for Sovtek tubes. So I told them to fuck off. I bought a matched set of JJ's and installed them myself. And to my surprise, Channel 1 now worked, but not Channel 2. :scratch::mad:

Fast forward a few years and I decided to open the top and take a look. I found a schematic on line and after looking for a bit couldn't find any suspect components or blown fuses at first. After removing the power tubes board, look at what I found:
TraceDamage.jpg

After following the traces, I find that the relay that switches from 2 mono 50W channels into 1 Stereo 100W output is the offending component. After a little closer inspection of the relay, I noticed it is ever so slightly deformed. One of the 2 destroyed traces is the ground for the relay.

I'm ordering a replacement relay now and I'm going to clean up the board and add some jumpers to the damaged traces. I've double checked the other components in that relay circuit and didn't see any other issues.

My question is this: Did the relay fail and switching to mono is what caused the apparent arcing that destroyed the traces? My other suspicion is that maybe some dust build up caused the traces to arc and that is what caused the relay to deform. When I first got the amp, it was quite dirty inside.

Any help, insight or concerns would be appreciated.
 

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Chances are too high of a voltage has been sent through it which caused the traces to burn out and the heat from that caused the deformation that you see.

This should have made a smell when it went up. So i'm guessing that this happened before you got it.

Can you post up the schematic and ill see if anything jumps out at me. Depending which position this is locked in you could have an impedence mismatch going on which could damage the OT.
Also another thing to note is these amps are an absolute pain in the ass to work on due to the way they are built so I would take it to a tech. The construction methods are total bullshit and nearly every tech that I know refuses to work on them as it's a nightmare with the folded PCB structure
 

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I dont know the cause but if you are replacing any suspect components you should be OK. A track repait kit, some board mask and good no-clean paste flux along with a fine solder iron tip will get it done. If you dont know where to get them hit me up, there is a bunch of choices you can narrow down by measuring them with a caliper... JIC a trace is basically a wite, if cleaning and repairing the bourd of burn damage gets tricky you can bare the bourd back with a xacto blade and solder fine wire between connections as well, just make sure to route it the same as the traces and make clean connection.

Through hole barrels can be tough, thats where useing wire may be best.
 

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Discussion Starter · #4 ·
Also another thing to note is these amps are an absolute pain in the ass to work on due to the way they are built so I would take it to a tech. The construction methods are total bullshit and nearly every tech that I know refuses to work on them as it's a nightmare with the folded PCB structure
I attached the schematic PDF. FYI, on the page with the board layout, the power tube board is a mirror image.

And yes, the damage was done before I had the amp and the other channel has been working fine for years with no problem.

This thing is a bit of a pain in the ass to work on, which is why I took it to the shop the first time. If I take it back again, I will have spent more money on it than it is worth and it would make sense just to get another one. I have some free time since I got laid off now and figured I'd try to fix it.

On a side note Bigdave, I have the equipment to measure and solder the traces. I also have some 43 gauge copper that I can use if that happens to be the thickness of the traces on the board. If not, I'll get one of those kits you mentioned.

Thanks guys!

View attachment Peavey-Classic50-50-Schematic.pdf
 

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For what it's worth, I've never had an issue bypassing a broken trace by just running a wire between the 2 contact points on either side of the break. Don't know if that's the 'correct' way to do it or if the electrical properties change as a result, but it's never caused me any issues.
 
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