Bending a DOD Grunge pedal [or trying to]

skotot · December 13, 2008, 08:20:32 AM

Hey guys-

I have circuit bent plenty of kids toys in the past and have taken electronics courses, so I am not a total stranger to all of this... Recently I have opened up my old DOD Grunge pedal, grounded it all and have a cd player running through it. I have a small resistor on my probe... I turn on the distortion and probe around the board, and some contacts (which I assume are the ones that short it out) turn the distortion off. Do you know of any way around this preventative measure? Maybe a higher resistance on my probe? Here is what I am bending... http://www.ultimate-guitar.com/reviews/guitar_effects/dod/fx69_grunge/

I have big plans for the functionality of this project that I cannot wait to share with you guys when it is all finished.

Thanks for your help!

-Scott

Gordonjcp · December 14, 2008, 05:45:51 PM

There's not really anything to bend in this. It's just a fuzzbox. You might try fiddling about with the feedback resistors on the opamps to get more gain, and thus more distortion.

This page has circuit diagrams:
http://filters.muziq.be/model/dod/fx/fx69b

They look a bit incomplete.

Gordon

skotot · December 15, 2008, 03:32:16 AM

Hmmm I thought that since it had programmable chips that it was would have been definitely trippable. Weird. Well that certainly puts a damper on a poor man's expedition...

I am planning on making a small control panel consisting of four or five toggle switches, two small pots, and a kill switch, all on a metal plate that will mount on a beater guitar of mine. It will connect to the pedal via a quick disconnect wire harness, so the controls can be used on other pedals as I bend them. Has anyone seen anything like this, or done this themselves? Just want to know some pitfalls others have run into with similar designs.

Gordonjcp · December 15, 2008, 11:57:47 AM

Quote from: skotot
Hmmm I thought that since it had programmable chips that it was would have been definitely trippable. Weird. Well that certainly puts a damper on a poor man's expedition...

I don't think there's any programmable chips in there, if it's anything like the circuit I found. What makes you think they're programmable? Maybe I've missed something...

Quote from: skotot
I am planning on making a small control panel consisting of four or five toggle switches, two small pots, and a kill switch, all on a metal plate that will mount on a beater guitar of mine. It will connect to the pedal via a quick disconnect wire harness, so the controls can be used on other pedals as I bend them. Has anyone seen anything like this, or done this themselves? Just want to know some pitfalls others have run into with similar designs.

Sounds like a great way to inject lots of noise into what is basically a very very overly-sensitive amplifier. You'd need to use extremely good-quality cable and connectors, and keep the cable short.

skotot · December 16, 2008, 12:00:59 AM

Yeah, those schematics don't appear to totally line up with the circuit in my box, unless I am totally missing something. My board has a 14 pin chip by TI, which I am assuming is programmable. Maybe I'm dead wrong here?

I've patched line outs on bent units before and have had no problem running them through amps... The controls I'm speaking of putting on my guitar would just be the switches to connect and activate shorts in the pedal; sort of an extension cord for the toggles... I use good wire [same wire we use in the lock factory I used to work at and would make 200 foot harnesses], so that all should be fine.

Circuitbenders · December 16, 2008, 02:21:21 AM

Quote from: skotot on December 16, 2008, 12:00:59 AM
My board has a 14 pin chip by TI, which I am assuming is programmable. Maybe I'm dead wrong here?

There must be thundreds if not thousands of 14 pin chips made by TI that could serve any number of functions, the vast majority of which will have nothing to do with programability. Surely he fact that you can't program a DOD grunge pedal is a give away $:-\$

rackham · December 16, 2008, 01:34:15 PM

Quote from: skotot on December 16, 2008, 12:00:59 AM
Yeah, those schematics don't appear to totally line up with the circuit in my box, unless I am totally missing something. My board has a 14 pin chip by TI, which I am assuming is programmable. Maybe I'm dead wrong here?

The 'chip' is going to be an opamp, according to the schem it should be 5 (or more likely 6) in one package (?). Have you googled the IC part number?