Peavey Classic 30 No EQ No Boost

[misterc57]

Now that the amp is working (after my squeal issue).

I find that all 3 EQ pots and the Boost switch have no effect on sound.

Looks like they are all in the same section of the circuit. Maybe a ground issue?

I have some poking around to do. Hopefully can test without pulling the boards out again. Any suggestions much appreciated.

Thank you, MarkO

[The Dude]

More than likely one (or more) of the board to board jumpers. They often break or come unsoldered when taking those things apart. Do a close inspection of those connections.

[Enzo]

Thus^^^^

Power off. Look at the row of bare wire jumpers between the boards. Get under each one and gently tug. If any come free, repair them.


Possible open VR6.

[misterc57]

Jumpers okay. VR6 is open from the wiper to both outer legs.

[Enzo]

Sounds like that is the problem. Extract the part and recheck it.

If it is indeed broke, the part number is 71190326. Peavey may have renumbered it to something like 31190326, or indeed something even newer, the parts people there will know.

20k S taper spider pot

[misterc57]

Extracted and still open. Waiting to hear from Peavey Parts.

Does it make sense that this also effected the Boost switch?

Thank you

[misterc57]

The Pot

Here is a pic of the opened pot. I think it was cracked prior to my opening the pot case.

Peavey said this; Can replace with 31190307, but the contacts are somewhat smaller on the new part....there needs to be a solid solder fillet on the replaced part and the leads should be bent before soldering for a better mechanical
connection/PCB fit.

31190307- 20K S TAPER MET SPDR 1MM
$3.79 ea

[Enzo]

Does it make sense that this also effected the Boost switch?

Yes, of course. Look at the schematic. That open pot kills the entire tone stack, the boost is part of that.

[misterc57]

Replaced VR6 pot. All is good now. Thank you!