Peavey Musician 400 Schematic

[vintagegear86@gmail.com]

Hello everyone
This is my first forum post. I recently bought a Peavey Musician 400, a non master model ... it needs to be refreshed, a couple of potentiometers changed. But I can't find a scheme for that model, so please help. I wrote directly to Peavey Electronic twice, I wrote directly on the Peavey forum but nothing, no answer.
Thank you all for your help.

[Jazz P Bass]

I have attached the schematic diagram.
Are the controls broken or simply 'scratchy'?
If they make noise in the output when turned, in my mind you may be better off trying to clean the controls before replacing them.
DeOxit works a like a charm.

[glebert]

Peavey used some weird custom pots back in the day, some with really long legs, or long shafts or bushings, etc. If you need to replace pots post pics and someone may be able to suggest a replacement.

I have actually been using turpentine on pots if deoxit doesn't get them working right. The old radio guys used it to loosen frozen potentiometer shafts, but I find it can (sometimes) help for wipers and tracks too.

[vintagegear86@gmail.com]

Jazz P Bass: Thank you so much for the answer.
Believe it or not, that’s not the scheme for my amp. The circuit you sent me is for Musician 400 but the version with master gain, master reverb potentiometer. So I attached a picture to see..I tried with the scheme you sent me and they differ literally from the input ... there are small touch points but that's not it ...

[vintagegear86@gmail.com]

Glebert: I found replacement potentiometers. I know they are different, I'll post a link for other users to see. Maybe someone needs it.

https://eu.mouser.com/ProductDetail/...z1LSJf4w%3D%3D

[Enzo]

This is for a different model of that series, but is this a lot closer?

[vintagegear86@gmail.com]

many things are missing in this scheme .. but thanks

[vintagegear86@gmail.com]

I can't believe the scheme doesn't exist ... I don't know why no one from Peavey Electronic responds to emails .... does anyone have experience with Peavey Electronic? Do they respond to emails, maybe I'm sending the wrong one

[Enzo]

Yes, I was a Peavey authorized warranty repair shop for decades. I don't know what email address you used, but this is the proper one:

customerservice@peavey.com

And their forum is for us, not them, so asking them for a schematic on their forum won't get results.

But I have been doing electronics for almost 70 years, and have even written magazine articles on doing repairs without schematics. SO I have to ask, just what are we trying to fix that requires schematics? Our earlier post was wrong because the input jacks were different and it had a master. Are your problems in those areas? The one I posted I think is right for your inputs and master, though other features are missing. The idea is this: if the reverb is broken, as long as we have a reverb section of the schematic, it doesn't matter if the input jacks are wrong.

I note, for example, that the NORMAL channel on both schematics is the same. The effects channel obviously differs through half the channel.

SO can we help in that way?

[vintagegear86@gmail.com]

I just checked, I used the correct email address.

Problem Description:

1. Fuzz didn’t work when I bought it. I took it to a friend who is much more professional than me ... He found out that someone before us put a high value resistor on the signal path between fuzz and gain (a friend put a capacitor in that place but we don't know the value of the capacitor..therefore and the fuzz color.But now I get the fuzz sound on the potentiometer.
2. When I turn on fuzz and amplify, there is a mixing of clean and fuzz signals, clean signal is very present. (maybe it should be, I watched all the presentations on YT but without much success)
3. When I amplify the distortion potentiometer .. a little over half ... there is a lot of constant feedback.
4. I have to replace the Gain pot on the effect channel, because someone put 50k instead of 10k value. The same goes for the bass potentiometer on a normal channel.

I don't think I forgot anything ... these are my problems

Dear Enzo, thank you very much.

[vintagegear86@gmail.com]

Would it help if I posted pcb pictures?

[Enzo]

Couldn't hurt. Posting is free anyway.

[J M Fahey]

I think your amp basically matches the "Musician 400" schematic from post #2
Maybe yours is from an earlier version without Master Volume control, but in any case your problem is not there, so ignore that section.

Like Enzo said, think of it block by block.
Newer versions are "improved" all the time, but not 100% redesigned from ground up by any means.

I bet, say, Fuzz is 90% the same at least.

1. Fuzz didn’t work when I bought it. I took it to a friend who is much more professional than me ... He found out that someone before us put a high value resistor on the signal path between fuzz and gain (a friend put a capacitor in that place but we don't know the value of the capacitor..therefore and the fuzz color.But now I get the fuzz sound on the potentiometer.

You sure you donīt mean "between Gain and Distortion" pots?
Because there is a 330 ohm resistor (your mystery component?) between them while there is a continuous track or wire between Fuzz and Gain ones.

2. When I turn on fuzz and amplify, there is a mixing of clean and fuzz signals, clean signal is very present. (maybe it should be, I watched all the presentations on YT but without much success)

It works that way, Fuzz never cuts or replaces clean sound [sigh!]
Donīt worry much about it, itīs a cheesy very dated Fuzz circuit.
If you like Fuzz (I do), use a good pedal ahead at will.

What do you mean by "amplify"? .... raise volume/gain?
Slightly confusing.

3. When I amplify the distortion potentiometer .. a little over half ... there is a lot of constant feedback.

Even if you unplug your guitar?
It may be plain string/pickup feedback.

4. I have to replace the Gain pot on the effect channel, because someone put 50k instead of 10k value. The same goes for the bass potentiometer on a normal channel.

Like Nike says: "just do it"

Even if some details differ, basic functional blocks, one by one, must be quite close.

As of:

I can't believe the scheme doesn't exist ...

, be realistic, that amp was made FIFTY years ago.

Be glad it WORKS (thanks to Peavey AWESOME reliability) and somewhat close schematics are available at all.

[vintagegear86@gmail.com]

What do you mean by "amplify"? .... raise volume/gain?
Slightly confusing.

rise volume/ gain


Even if you unplug your guitar?
It may be plain string/pickup feedback.

I'll try without a guitar and cable.

Tomorrow the amplifier will be in my workshop again, I will photograph and share everything in detail. Then things will be much clearer Thank you very much.

[Enzo]

Guitars can feed back and cause other things, but for test purposes, you can try a different source. I used to use a CD player or other source of music as a test signal. No way iut wil feed back.