Repair Issue w/Green Russian Big Muff

[effectsbay]

Hello All

The other guitarist in the band found his old Big Muff that's seen some serious abuse. I wanted to see if I could get it up and running. I'm running into a few problems, and was hoping that someone might be able to steer me in the right direction.

First off.. issues. The battery connection was hosed. I ended up attaching a 9V plug to it. So far so good. Next, I noticed that the Distortion pot was completely broken. This is the older Russian Muff with the long posts. I did some Googlin' and found that they're using Russian parts, but a B100k pot will work. I soldered that. Output lead was disconnected from the footswitch so attached that. Thinking I was on my way, I'm noticing the following issues.

When bypassed, the guitar signal goes through as expected, bypassing the circuit. The problem happens when the pedal is activated, no signal flows, but if I jumper the output of the board to output lug on the switch, I get constant oscillating/tone. All pots affect the tone, but you do not hear any guitar.. and the tone is constant. Obviously jumpering is not ideal here, and probably 10000% wrong, but just trying to problem solve.

I inspected all other solder connections, and everything seems good. I checked continuity throughout the board, and that looks good too? Non of the components look fried.. no burning/charing or discoloration. I'm almost suspecting the crazy switch.. any ideas?

Thanks!
hank

[electrosonic]

I traced my friends Big Muff Pi because his sounds so good and I wanted to verify the component values.

If this is any help I took a photo of the board and labelled the components.



The component numbering follow the Beavis Audio Schematic found here...

http://www.beavisaudio.com/schematics/Electro-Harmonix-Big-Muff-Pi-Schematic.htm

If I were you I would put a signal in (output from and MP3 player is fine) and trace the signal through each gain stagel.

Andrew

[effectsbay]

Thanks for sending that.. my board is different. Also my footswitch doesn't follow existing schematics.. quite weird.. I'll include the board and switch here:





Thanks!
hank

[effectsbay]

This is the schematic that comes close:

http://www.kitrae.net/music/Images_Secret_Music_Page/V7_7D_Wiring_Diagram.pdf

In the schematic.. the footswitch looks like
Ground | Dist | LED
Output | Input | Vol

Mine is looking like
Input  | Vol  | Output
Ground | LED | Dist

Thanks again.
hank