Peavey Ultra Plus - No Clean and switching issues

[stereomonostereo]

Hey guys,

I'm trying to get to the bottom of some problems with a Peavey Ultra Plus head. First, the channel volumes are really low. With the footswitch, i am only able to active the Clean and the Crunch settings. Ultra does not activate and the light does not come on, as is the same with the effects bypass. I can jump from pin 4-5 and from pin 4-7 to get the relays to engage. When i plug into the effects return i'm getting a strong output signal, so i believe it's in the preamp.

The schematic has me a bit turned around as to what relay is in charge of what, and these clamp circuits always lose me. It seems like something is blocking a portion of the signal before V3 or V4. The switches in the foot pedal all seem to be fine as do the LEDs. Any insight as to what relays/diodes/transistors i might want to look at and what voltages should be there?

Peavey-Ultra-Plus-Schematic.pdf

[tedmich]

Often its one of the JFET muting transistors gone bad, see here
http://music-electronics-forum.com/t248/

[stereomonostereo]

Well it seems i'm getting zero voltage at Q5 and Q7 which are both part of Clamp C. Looking at the schematic i'm not sure what voltage i should be seeing at the gate. I believe i should be seeing about +20

[Jazz P Bass]

That schematic link is dead: Ultra Plus schematic.zip

[stereomonostereo]

UPDATE: With Q5 removed the signal returns at the volume it should be. I'm still missing the ULTRA switching and the Effects switching on the pedal, but it's progress

[g1]

I can jump from pin 4-5 and from pin 4-7 to get the relays to engage.

Maybe I'm misunderstanding as this says to me that the problem is in the footswitch?
Or are the relays engaging but not doing their job?

[stereomonostereo]

Pins 4-5 switch from Ultra to Clean, Pins 4-7 switch from Ultra to Crunch. Those are working correctly at the plug. I believe that if i jump 4-6 i should be hearing the relay engage for the effects bypass and i'm getting nothing.

[stereomonostereo]

Here's my footswitch wiring

[Enzo]

WHAT FX loop relay? There is none, the third stomp switch runs the reverb, and that has no relay, it is done with JFETs.

If this is not working switching, look to your pedal and cable.

[stereomonostereo]

My bad, the pedal has it labeled Effects Bypass. I'll check the pedal again

[Enzo]

pin 4 was ground? The two other pins were live relay coil circuits, so maybe 24vDC? So inside teh switch unit, either the common has continuity to amp ground or not, the incoming hot pins either show their voltage on the switches or not, and the switches either close or do not. If any thing is missing, then look to teh cable for either a broken conductor in one or more of the wires, or for broken solder on teh DIN plug.

[stereomonostereo]

I'm getting +24 at pins 1,2,3,5, and 7 and -17 at pin 6 with the Channel switch pressed in on the front of the amp. I have the reverb working, but i had to reverse the red and black LED leads in order to get it to function. Currently the rest of the footswitch is wired according to the above diagram. Here's what i've got:


Crunch Channel Activated
ULTRA and CLEAN LEDs on


Clean Channel
CRUNCH and CLEAN LEDs on


Clean Channel
CRUNCH LED on

It's almost like the CLEAN and CRUNCH LEDs are working backwards. Could this use a different wiring diagram considering the REVERB switch didn't work until i reversed the LED from the diagram?

[g1]

The diagram you posted does not show the polarity of the Led's.
Did it work with the amp before? Is it made to work with this model? Has someone rewired it to work with something else?

[stereomonostereo]

The diagram has them labeled Red and Black which i just assumed was positive negative. Someone was definitely in here before. I returned it to the wiring diagram and that's where i'm at now

[stereomonostereo]

I've got it sorted. The red leg of the CRUNCH LED gets wired to pin 1. The red leg of the CLEAN LED gets wired to pin 3. The REVERB LED gets the black leg wired to pin 2. Why this one is different is beyond me.