Help me diagnose crackling problem

[Guitarfreak]

The pedal is a reissue model NYC muff.  The noise is quiet and in the background, the tone is not affected, but it is still noticeable.  Mods include:

Tone Bypass (bypasses tone stack)
Cap Bypass (bypasses the 460pF caps on the gain stages
Diode mod (Use 4PDT to get Si in one position, Ge/LED in the other)
Modded the 470k collector to base feedback resistors to 330k

I started getting the noise after the Diode mod, but have since reflowed all of the joints and the problem remains.  I am not sure where to start, but there is a lot going on in this pedal so I would appreciate some advice regarding its diagnosis.  Here is what the noise sounds like.

http://soundclick.com/share?songid=9675393

[Guitarfreak]

Anything?

[goulashnakov]

What I've always been told as a good place to start:

1.)  The trusty ol' "Debugging" thread.  Don't leave home without it!  (But DO read and follow the thread's instructions to a Tee.)

Reason being that, while to some it may seem only appropriate for a pedal that doesn't work at all, and that going and getting all those voltages may seem tedious, extraneous, boredomeous, (and any other "-eous" you can think of  ); nonetheless it's still possible that a schytt component may throw off your woltages, which in turn may cause unwanted noise issues.

And...

2.)  Audio Probe.  That can help you quickly isolate or at least narrow down in what part of the circuit you're getting the noise, and then you can use that to determine if it's a bad component, faulty wiring/soldiering/etc/etc/and-what-have-you.

If I had a nickel for every time the audio probe has helped me tremendously... well then I'd probably be buying pedals instead of trying to build them!  =D

I listened to the clip, and my first gut-instinct is a bad part or connection.  BUT... instinct alone isn't what made humans the superior species, and I am NOT the go-to man when it comes to "gastro-inductive reasoning."  Audio probing and "standard debugging procedure" are a good place to start.

As my old Grandpappy used t' say (except, not really =D) "probe first, ask questions later."

Peace.

[Guitarfreak]

Well that certainly helped.  I had a BYOC 'signal tester' lying around unused because I wasn't sure how to use it, but the link you gave me explained it well.  I used in on the Muff just now and have narrowed it down to the caps involved with the cap bypass mod.  The crackling is so loud now and now I don't even get any signal or barely any at all (I may have agitated the problem with a recent mod).  Damn those Ceramic caps, they sound so good but they're so fragile!

[Guitarfreak]

OK, I wanted to diagnose this myself without getting any help from anyone else, but I've been probing things, metering things, and soldering things since last night with no luck and no end in sight.  After all of the mods I did last night I was able to make comparison clips, a.k.a. the pedal worked, then all of a sudden it just stopped.  The LED still lights up and when I pick hard there can be intermittent crackling sound heard, but otherwise there is no sound at all when activated.