MP-2 Auto-wah has no output

[miker1012]

I don't get any output from my presets that use the auto-wah. Does anyone know what can be causing this?

[Dante]

I'm not near my MP-2 right now, but have you tried maxing out the values? Just wondering if they're silent when turned all the way down (?)  :dunno:

Otherwise, there is a MP-2 Wah fix...not sure if I already have it and just haven't posted it yet....I'll look around

[miker1012]

Dante,
Thanks for getting back to me. I have tried to max the settings. No output still. Any help would be greatly appreciated. I just bought another MP-2 off of Ebay, but I haven't received it yet. I may be able to troubleshoot this once I have them side by side. I do own a o-scope and volt-meter. So maybe you can tell me where to look and what levels I should see.
Mike

[rnolan]

Hey Mike, if you check out page 2 of the manual (http://adadepot.com/index.php?topic=112.0), the wah is after the compressor and before the tubes (input > comp > wah > tubes etc).  So sounds like there is an issue in the wah circuit, i.e. when you turn it on signal stops progressing, off all works well.  Hopefully Dante will come back with some useful advice re the fix (if that's whats wrong), alternatively MJMP may be able to help.
Cheers Richard

[MarshallJMP]

is it only auto wah or any of the 3 wah types?

[miker1012]

Appears to be all wah types. I don't have an expression pedal hooked up, but all wahs are DOA. I replace U205 and U207 with no change in symptoms.

[miker1012]

I'm a knucklehead. The Compressor kills the output too. I just saw the manual that was pointed out to me previously and I figured I better check some presets with the compressor on. Sure enough it cuts out completely when I enable it.  So this appears to be a major fault. Any help would be deeply appreciated.
Mike

[MarshallJMP]

The compressor is a known problem with mp-2's,but i haven't found a solution for this.It's a very strange problem.Now usually the sound returns usually after a few minutes to an half hour.

[rnolan]

Hey Mike, from the manual schematic, both the compressor and the wah can be bypassed (in/out) so, just to confirm, when you have the compressor off/out, does the wah (on/in) still not work ?? (i.e. is it one or both?)

The compressor is a known problem with mp-2's,but i haven't found a solution for this.It's a very strange problem.Now usually the sound returns usually after a few minutes to an half hour.

don't you just love these NOT!, hey MJMP, while this is well out of my league but, are there any shared bits of circuit between the compressor and wah ? maybe there's a relationship ? just a thought.

[MarshallJMP]

No,like i said it's a strange problem,my 3 mp-2's have this problem.I even replaced the whole switching system with all new components,didn't help.

[miker1012]

FYI ~ I replaced the TC9164AN at U202 and it didn't help. I've also replace the Op-Amps at U205 and U207. I think I'm ready to give up on the Wah/Comp.

[rnolan]

Bummer, although it's not the end of the world, the MP2 is still a hot preamp without comp/wah, I very rarely use either these days.

[miker1012]

There is still one other part I may try to replace and that's U210. It's the SSM2120 that is a part of the Wah/Comp circuitry. I'm just spraying bullets here, but who knows maybe that's the culprit.

[MarshallJMP]

You could try but i doubt it will help.From what i could measure it comes from the switching.