Peavey 5150

[MarkusBass]

I've got Peavey 5150, which I was told makes some strange noises. I couldn't reproduce the noises but I found this:

This is the connector between the power valves board and the main board of the amp. It was already fixed (with two additional wires) but the board may be conducting. I think that I have to remove carbonized board and see what else is wrong with the amp. I also need to replace 100R grid resistor. It was already replaced by some lazy guy with a huge resistor taken out of probably a russian TV. I need to fit a proper one. How do you remove the power valves board?

Mark

[52 Bill]

How do you remove the power valves board?

Mark

You have to drill out the rivets that hold the tube sockets to the chassis. Use pop rivets to reinstall the assembly.

[Enzo]

You refer to the screen grid resistor? You don't need to remove the power tube board.

Find the resistor you need to replace. Unsolder it, and poke its leads out through the holes so it falls into the chassis loose. Fish it out and throw it away. Now install the new resistor on the solder side of the board facing you. The resistor won;t care which side it is on. Make sure to trim the excess wire leads before doing this.


However Bill is correct, if you DO want to remove the power tube board, you drill out the 8 rivets. Then 8 new pop rivets will reinstall the board. DO NOT unbsolder all the socket legs.

[g1]

I also need to replace 100R grid resistor. It was already replaced by some lazy guy with a huge resistor taken out of probably a russian TV. I need to fit a proper one. How do you remove the power valves board?

Maybe you thought they were lazy because they put the resistor on the foil side of the board? Don't worry, in many cases this is an acceptable factory technique. Sometimes it is just not worth it to remove the board. The best example I know of were the Fender Super60 amps. If you go to all the trouble of drilling out the rivets, cleaning up the metal filings, and reassembly with new rivets, you will see why the "lazy" guy did it that way.
If the resistor is too large I would suggest replacing it with a proper size one on the foil side of the board, using the technique Enzo described.

[tedmich]

Hand Riveter Set
$4.99

[MarkusBass]

Maybe you thought they were lazy because they put the resistor on the foil side of the board? Don't worry, in many cases this is an acceptable factory technique. Sometimes it is just not worth it to remove the board. The best example I know of were the Fender Super60 amps. If you go to all the trouble of drilling out the rivets, cleaning up the metal filings, and reassembly with new rivets, you will see why the "lazy" guy did it that way.
If the resistor is too large I would suggest replacing it with a proper size one on the foil side of the board, using the technique Enzo described.

You are right, it was to much work to remove the board. But the guy put such a resistor instead of the old one (the old one is not even removed):

It's huge but I'm not sure if it can handle 5W power - they were of very poor quality. Saying "lazy" I also thought of the other problem; the carbonized PC board. The guy made shorts to bypass the plug but the board is still conducting. Fixing this would require removing the main board. This does not require drilling the rivets but you have to take care of all pots, all Jack sockets, and so on.

Thanks for the explanations with the rivets. It's possible that I will install the resistor from the top.

Mark

[MarkusBass]

OK,

so I was also lazy and installed the resistor on the foil side of the board. The old resistor was 91 Ohms, 4W only (despite its size).


I also removed carbonized board and installed new socket. All problems are gone and the amp sounds great. It's a very good amp .


Thanks for help and the explanation about the power valves board.

Mark