wah pedal (dunlop) troubleshooting problems

Started by SnooP_Wiggles, February 20, 2005, 02:09:40 AM

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SnooP_Wiggles

I've been trying to fix a wah pedal that was broken. So far i've replaced a few caps and a broken inductor (with nice fasel). But When effect is engaged the signal is same as bypassed just loses some bass and is a tiny bit louder (the louder bit is intentional). rocking the wah does absolutely nothing to the signal.

I was thinking maybe the Q2 transister was stuffed or something but i don't like replacing transisters unless i have to (fiddly nasty things). I tried audioprobing but just found that Q1 amplified the signal but nothing else changed after that. i can post multimeter readings if that helps. Any ideas on what it might be? i had a look at 'technology of the wah pedal' but couldn't find anything to help me there.

jimbob

Sounds like a bad inductor. (even though its been replaced) Try another one.
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SnooP_Wiggles

doubt it. brand new fasel inductor from aron. i measured 20-21ohm resistance across the 33k resister (mine is 22k because its going to have a 50k pot next to it to adjust Q). the jim dunlop website mentioned that inductor was open if that measured over 100ohms

Travis

You might want to try an audio probe.  Rule out structural problems first.

Give us transistor voltages if you can't solve it with the probe.

SnooP_Wiggles

tried audio probe no help

Im not sure what you want by transister voltages so i've measured them with respect to ground...
(battery measured at 9.13v with multimeter battery tester)

Q1: B- 0.7V
     C - 4.7V
     E  - 0.1V

Q2: B- 8.3V
     C - 2.8V
     E  - 3.1V

SnooP_Wiggles

i think i've found a/the problem. i was measuring the resistances across the wah pot and found that they didn't change much at all between extremes:

looks like pot needs re-glueing to pinion geer....