Big Muff repair

[cixot]

Hey
I'm trying to repair a Big Muff (the Op-Amp version) and just ran into some trouble. While debugging it with a multimeter, I found what looked like a damaged resistor right where the problem seemed to be. So I figured I'd just desolder it and measure the Ohms. Doh! As I was gently pulling it out of it's hole, it actually broke in two! Makes measuring a real hassle, and the colour codes were scraped off as well (it was like that before I started desoldering it though).
The resistor was placed between the black wire in the 9V DC jack and the +9V in the circuit. The schematic below is my best find so far, and I can't find that resistor there.  Maybe I've gone suddenly blind or something, I dunno
Anyhow, what I'd like to know is of course what the value of that resistor should be, and also what's it doing there?

(EDIT)
Forgot this...

http://www.geocities.com/j4_student/bigmuffopamp.gif

[Ge_Whiz]

It sounds more like a protection diode that sacrificed it's life trying to protect the circuit from a power supply of the wrong polarity. A silicon diode of the 1N4001, 2, 3... series should do, wired cathode (stripe) to +9V. Take it right out, and see if the circuit works without it. If not, it died in vain...

[petemoore]

  DIY...is fixing a pedal...if you're Doing IY.
  Before powering up a circuit, -the protection diode, a test for NON continuity between V+ and ground is a good idea.
 

[cixot]

Ge_Whiz:
The thing is, it doesn't look like a diode whatsoever. It looks like any other regular resistor; a yellow/brownish base colour, slightly thicker near the edges than in the middle, and it does look like there were stripes on it once upon a time.
Also, if it was a diode, then I should be able to just stick a wire there instead, as long as I don't flip the polarity. What happened then was that the battery started to drain pretty fast (maybe a loss of 0.1V a second). That did not happen before it broke off 

To give you a better idea of what I meant with my previous description of this components placement, I took a photo and added some comments to it..

The 220uF electrolytic is placed in the far left of the schematic previously posted...

If you're wondering what those black blotches are, I think it's burnt soldering flux, or whatever that orange stuff is around the potentiometer pins. Someone on another forum suggested it might be old soldering flux, and when I resoldered a few wires, it got burnt. Looks ugly but it doesn't seem to cause any trouble.

[Dan N]

The last schematic has that resistor as an unknown value.

http://www.singlecoil.com/docs/vintage_muff.pdf

The note mentions to try a 47E. I don't know what E means. 47ohm? 4.7 ohms? Anyway, just something very small.

[cixot]

Ahh, cool. Thanks!

I think 47E means 47 Ohm. The resistor code RA47E0 refers to 47E in this page: http://www.web-tronics.com/irremcondimk.html
And in this page it refers to just 47 Ohm: http://www.web-tronics.com/irremcondimk.html

[cixot]

After much procrastination, I finally got around to actually trying to fix this. I replaced the missing resistor, which seems to have been a 47Ohm, with a 100Ohm (all I had then). So now I'm at least getting sound from the pedal. However, there are still some issues:
1) The box has a on-off switch for the tone control. It sounds OK when it's off, but when I turn it on, I can only get very trebly sound. If I turn the knob for a more bassy sound, the volume is gradually lowered. Obviously, the pedal can't deliver any bass in this mode.
2) Like I said, I get decent sound in the off mode. But it sounds very much like an old muddy amp. Maybe it's supposed to sound like that; I don't know because I always used the Tone control for a sharper, less muddy sound.
3) The sound also sounds kind of... crappy. It's crackly and noisy, especially when I turn up the Sustain. Could this be worn-out OP-amps? Or the fact that I inserted a (probably) higher value resistor on the voltage supply?

I'm grateful for any ideas on how to solve this. 

[sfr]

Two 100 Ohm resistors in parallel should give you 50 Ohm.  That should at least get you closer to the 47ohm.

[petemoore]

  R17, looks like a 47 ohm, and also looks like it's used to help filter PS noise, placed between V+ and the Supply +.
  100ohm is a common value, 47 ohm may do all the noise cancelling of a 100ohm, and the circuit should otherwise 'work' with this part removed/jumpered..as maybe it just helps remove a little bit of ripple from the PS.