Colorsound Supa Tonebender reissue has got me stumped

[PEPPER!]

Hi!  I have a friend's Colorsound Supa Tonebender on my desk and I've spent way too much time with it not to ask for help.  I suspect it's a simple problem unrelated to this specific circuit and totally related to my ignorance and inexperience, but I am stumped.  Here goes.  I'll take pictures if requested but let's start with these identical ones from the Internet.

The pedal - Colorsound Supa Tonebender "Steve Hackett" reissue:



My friend's looks exactly like that except it's all beat to hell.  As some of you might know this isn't a classic Tonebender circuit but a Big Muff minus the clipping diodes on Q1:



The guts look so much like the ones in this FSB post that I'm just gonna put them here:







My friend broke the stomp switch and asked me to replace it, and asked if I'd add an LED and 9V DC jack while I'm at it.  Everything inside is stock except that he reversed the In/Out jacks as they were the opposite of every other pedal he or anybody else has ever owned (In on the left, Out on the right).  The wires were long enough that he was just able to unscrew the plastic nuts and swap without soldering.  The other odd thing about the wiring is that the output jack seems to be the one which disengages the battery.  Man, the 70s were wild! Anyway I take everything out and drill some holes, then install a 3PDT stomp, an LED bezel and a plastic 9V DC jack.  Before soldering everything I hook it up to my testing rig with alligator clips, and it behaves like the jacks are wired backwards -

 - bypass (the purple wire here) works fine
 - effect out (adjacent yellow wire, trace runs from Volume pot) gives me nothing

I figure my in/outs must be backwards, but I double check and they not.   Then, by accident I notice a strange thing - if I clip the bypass AND effect out wires together the output is the normal sound of the pedal, plus howling oscillation from a feedback loop.  Again, bypass is normal, effect out gives no sound, both together are fuzz + oscillation.  Weird.  I tried tapping the middle lug of the Volume pot to hear the output, but it's silent. Extra Weird.

The next thing to do is check voltages.  I'll spare you the exact measurements because every leg of Q1-Q4 is between 8V and 9V.  There is DC all over this freaking thing.  I check the DC jack wiring and it's not shorted, and I'm using the same Boss 9V adapter I use for everything else on the bench.  I check the polarity, try different wall warts, even a 9V battery, and I get the same thing.  I was concerned that maybe I applied the power backwards at one point and fried it, but the fact that I can get the normal distortion sound of the unit with added oscillation makes me think it's just something I've wired incorrectly.  

Anyway I've messed with it some more and gone over the PCB with a loupe looking for stray or lifted traces but haven't found anything.  I'm starting to think it's haunted.

Any ideas?

[induction]

PEPPER! wrote

every leg of Q1-Q4 is between 8V and 9V.

This sounds like a missing ground connection. If it worked before you took it apart, then one of the ground wires probably came loose when you were working on it. Reflow the solder joints at the ground wires (and any others that look dodgy), and see if that fixes it.

If it doesn't, measure the voltage at all of the ground traces on the board, jacks, etc. Check the wires themselves, the solder joints and the traces. Use the battery negative terminal as the reference voltage (ie. put the black DMM lead there), and find any ground point that doesn't read 0V. See if you can find precisely where the reading changes from 0V to ~9V. That should tell you where to find the bad solder joint, cracked trace, or whatever.

Let us know what you find.

[Frank_NH]

I agree with Induction here...sounds like a problem with ground.  Hopefully an easy one to sort out.   If you still have trouble, upload some photos of your PCB (the ones above are from FSB).  Good luck!

[PEPPER!]

Solid advice . . . I'll get to sit down with it again this weekend and see if I can sort it out.  Will report back either way but if there's still a problem I'll post pictures of the actual guts I'm working with.  Thanks!

[PEPPER!]

It lives!  The problem was two(or maybe three)-fold:

  - I reflowed the grounds.

  - C2 was crumbling to pieces and trace was lifting a little, so I replaced it.

 - I mentioned above that the output jack was originally the one that connects the ground when it's plugged in, but I hadn't thought that through completely in terms of the PCB layout.  Long story short, I was still mixing up left & right and hadn't traced the relationship between the jack grounds and circuit grounds properly.  

Thanks for the advice!  I just needed a little perspective as this was driving me nuts.

This is a cool Muff variant & skipping the clippers at Q1 makes a bigger difference than I would have guessed.  I was clearing out a relative's house recently and I found my old 70s Little Big Muff - it's the one with the same PCB as the full version but it's just wired up with volume and a tone switch.  I've been meaning to add the rest of the knobs for a while and this has made me think I'll probably add some clipping options as well.