5150 hideous death

[tedmich]

I picked up a dead 5150 "signature" model Peavey for very cheap and was hoping the Q7 switching JFET had gone out like the 6505+ I just got...opened it up and was met by this:



again I am a victim cause I have no sense of smell!

two SGRs were open and several other resistors cooked, but it was the "protection diodes" which nuked the PA board

Since I have the 6505+ open I can sub in its PA board to see if 5150 is worth fixing. Looking at the older PA board I figured I could make a newer version one faster (and cheaper) than ordering one from PV, so I etched one.

The old sockets don't fit without some lead bending, and it won't ever look stock but WTF. I moved some traces and tied the pin 1&8 on the last tube so EL34s could work if I mod the bias. I think I'll go with 2 parallel 1.5k 3w SGRs.

Now to fire up the old tube tester to see which (if any) of the 12 Ruby 6L6s are good...

[Enzo]

Those diodes probably saved your OT. That is their job.

[soundguruman]

Burning of the output board is pretty common on Peavey amps.
And the board is riveted to the chassis...
They usually won't sell new boards to repair it.

Any black carbon on the board will continue to burn, until it is completely removed. So, the board is often JUNK.

However, mounting regular sockets on the chassis,
you can point to point wire it.
It's been done many times successfully.

[Enzo]

Once again...

The board is not riveted, the sockets are.


And in my experience over the decades is that such a board burn is NOT common.

And furthermore, they WILL sell you a new board if they have one.

[soundguruman]

Once again...

The board is not riveted, the sockets are.


And in my experience over the decades is that such a board burn is NOT common.

And furthermore, they WILL sell you a new board if they have one.

Usually burns cause wrong impedance speaker, or bad speaker cable.
Starts arcing, and continues...
601 483 5365
Let's see how easily you can buy one....hahahahahahahahah! (good luck)
(all previous attempts to buy output boards have failed, that's what's funny)

[tedmich]

i like etching boards so I decided to do that, I did move some traces so I could put in 6 small holes for a hex key to tighten some socket head screws to test fit it without rivets, gotta be sure the main board is AOK as R69 (4.7k) blew up pretty bad.

You are right Enzo PV would sell me a new PA board but I am cheeeep. Main board is also available from PV... for about $350!

Its refreshing to have two sides to tech issues now; Enzo on the right and SGM on the left!

[Jazz P Bass]

That does not look like 'ordinary' damage.

Ten to one there where multiple attempts at fuse/ tube replacement & then the fire started.

[tedmich]

yah guy seemed deceitful but he had a really cute 4 yr old and the price was LOW, and I like to think I can fix anything (or at least anything as simple as 1st gen 5150!)

[The Dude]

Yep, as Jazz hinted. Be sure to check all fuses and make sure they are the correct value. Chances are good you'll find a 20A fuse in there.

[Jazz P Bass]

In the case of those high voltage diodes, they can fail short.

[Enzo]

That is what failed and burnt - the OT protection diodes.

[tedmich]

I think I'll replace them with RGP02-20E, 2kv 300ns at 0.5A for $0.20 each

[soundguruman]

That does not look like 'ordinary' damage.

Ten to one there where multiple attempts at fuse/ tube replacement & then the fire started.

I can't even COUNT how many output boards I have seen burn in PV amps...just like this one.
So, if you fix a lot of PVs, it's "ordinary." (as I have since mid 1970s)

This is why many times, they just mount sockets, and wire it PtoP.
Fiberglass may not be an "ideal" material...

But don't be discouraged, plenty of them have been salvaged plenty of times.

However what you don't want to do, is reuse a burned board, cause it will just keep burning.

[g1]

If you can't count that high or don't have extra fingers, how about just a rough guess and tell us.
You make it sound like it is a large percentage of all the Peavey amps you have serviced.

[Enzo]

See, the problem is that the fingers on one hand look a lot like the fingers on the other hand, so the count gets confused.

Anyone who works on amps for a living knows this is a lot of hot air.



Then again, even with my shoes off, I can;t count past 21.