Peavey MX VTX Reverb Not Working

This forum is for talking about all kinds of Peavey guitar amplifiers.
Post Reply
Telecastoff1
Member
Posts: 12
Joined: Sun Jul 26, 2020 2:08 pm

Peavey MX VTX Reverb Not Working

Post by Telecastoff1 » Wed Sep 08, 2021 5:39 am

I have a Peavey MX VTX amp with a non-working reverb. I checked the cables, the pan for broken wires and continuity. When I move the amp, I can hear it go "boing", but not very loudly as I would imagine. I'm pretty sure I have figured it out to be a bad IC, but I don't know which one controls the reverb. Anyone have any idea? I have a few extra IC's I removed from a Special 130 upgrade that I can swap out for the bad one(s), but don't want to indiscriminately be pulling IC chips with my fingers crossed, hoping for the best.

User avatar
Enzo
Member
Posts: 9535
Joined: Fri Sep 12, 2008 10:24 pm
Location: Lansing, Michigan

Re: Peavey MX VTX Reverb Not Working

Post by Enzo » Thu Sep 09, 2021 10:38 pm

Well if you want to try a swap, U4 is the reverb, and it is the chip snuggled right up against the molex connector for the reverb cables.

Telecastoff1
Member
Posts: 12
Joined: Sun Jul 26, 2020 2:08 pm

Re: Peavey MX VTX Reverb Not Working

Post by Telecastoff1 » Fri Sep 10, 2021 5:56 am

Thanks Enzo...I appreciate the info you gave. I swapped out the chip and the results didn't change a thing. I even pulled the matching reverb pan and cable from my Heritage VTX and tired it in the MX, but no difference. So, now I'm looking at something else, less-simple going on with the reverb output. I don't really need to use the internal reverb, as I have a pedal that can do that, but it would bug me to no-end with something not working properly on the amp. Any ideas in what I should look for next to repair this?

User avatar
Pappy B
Member
Posts: 762
Joined: Sun Jan 31, 2016 2:30 pm

Re: Peavey MX VTX Reverb Not Working

Post by Pappy B » Mon Sep 13, 2021 4:42 pm

If you haven't done it already, use some contact spray (Deoxit or similar) and clean/spray all the connections and the control pot. Those RCA and Molex connectors get corroded and can cause erratic operation.
The more I learn the more I realize how much I don't know.

Telecastoff1
Member
Posts: 12
Joined: Sun Jul 26, 2020 2:08 pm

Re: Peavey MX VTX Reverb Not Working

Post by Telecastoff1 » Mon Sep 13, 2021 10:31 pm

Thanks Pappy B. I've cleaned the pot(s), Molex connector, jacks, etc. Even changed out the Reverb/Molex cable and pan. Still the same. Very faint reverb noise when amp is shaken or tapped, but extremely faint reverb signal when the guitar is played.

User avatar
Enzo
Member
Posts: 9535
Joined: Fri Sep 12, 2008 10:24 pm
Location: Lansing, Michigan

Re: Peavey MX VTX Reverb Not Working

Post by Enzo » Tue Sep 14, 2021 6:03 pm

Alright. Reverb has two halves, drive and return. Your return side is not working, otherwise you'd have a loud crash when you whack the pan. So troubleshoot. To make a test signal, you can run th pan springs, or just unplug the return cable and touch the tip with a finger to make loud hum.

Oh, did you make sure the cables were in the right holes? You have two cables, touch the tip of each, one should make a loud hum, and that one would go into the OUTPUT jack on the pan. If neither makes hum, then we are back where we were a paragraph ago.

If so... Make a signal, is it present at pin 1 of U4a? Still present on the other side of C32? At R61? If the chip is OK, my suspect is that little 2uf cap. Peavey used a zillion of them back in that era. And that was 40years ago. On all the amps in that series I encounter, almost every time, all the little 2uf caps need replacing.

If you run out of 2.2uf caps, a 4.7uf cap will work fine too.

But trace the signal along first.

Telecastoff1
Member
Posts: 12
Joined: Sun Jul 26, 2020 2:08 pm

Re: Peavey MX VTX Reverb Not Working

Post by Telecastoff1 » Tue Oct 12, 2021 7:34 am

Thanks Enzo...That was it! That little 2.2uf cap at c32 was the trouble. I REALLY appreciate your help with this. Now this amp is in perfect working order.

Post Reply