Help Debugging Rat: I've tried everything besides rebuilding the whole thing...

[elenore19]

The issue is that the pedal is WAY too quiet for what it should be. At first the filter just wasn't working and it sounded fine, then I replaced the filter pot and the pot worked, but now I'm stuck with the terrible signal loss.
I found that when I make a bridge here (picture) that it has the volume, but the filter control doesn't work.




I've checked all resistor values, I've checked probably about 10 times for solder bridges, I've replaced the filter pot, I've replaced the 5458, I triple checked the wiring, I checked the polarity of the capacitors, I checked the voltages on the IC and transistor, and still I'm having my issues.

I'm completely stumped. I'm almost to the point of just having no filter control and just volume and drive.


Thanks for any help you can give. I really appreciate it.

-Elliot

[ACS]

If you have a look at the schem for the Rat, you'll see that the filter pot is a critical point - a failure there means basically NO signal will pass.  You're 99% of the way there - by bypassing the filter pot, signal was restored.  That's great news!

When you bypass the filter pot, how would you describe the sound? (even better, do you have another Rat to compare to?).  I'd expect the sound to be VERY trebley, very nasty.  If so, then I'd be pretty sure your circuit is A-OK, and it's just something in the pot or the wiring to the pot that's causing the issues...

Working on that premise, work through the 'things that could be wrong' systematically.  Make a list, check them off one at a time, and don't move on until you're certain!!

1. Pot.  Yes, I know you've changed it already, but it's possible to get two faulty ones (and I've certainly buggered them up in the past via dodgy soldering).  Check that it's showing the right resistances at fully clockwise, counter closckwise and a few points in between.
2. Wires.  Check each of them for continuity.  It's possible you've got a break in there somewhere.
3. Soldering of wires to pot and wires to board.  Check for continuity from trace to solder joint, trace to wire, trace to other end of wire, trace to pot solder joint.

That's it.  If the bypass is giving you a working circuit, then one of the above /should/ be your culprit.

Good luck!

Aidan

[MikeH]

Have you used an audio probe to trace the signal through the circuit?  If you do you will be able to find the spot where signal loss is occurring.