Weird Wah Problem

[bluetubes]

Hi all,

I need some help!  I have a 80's Dunlop GCB-95 Wah pedal and I have completed two mods

1) Vocal Mod - Changed 33K resistor in || with inductor to 68K
2) Midrange Mod - Changed 1K5 resistor at the Base of Q1 & Inductor to 2K2

Pedal sounds great......until I put the bottom plate on.  Once the bottom plate goes on...the thing starts to howl and picks up radio stations.  It's the weirdest thing.

Anybody have any suggestions for this noob?

Thanks,
BT

[bluetubes]

Problem solved.   Undid the midrange mod and pedal is now acting normal again.  Not sure why it happened but it's fixed now.

Cheers,
BT

[Pedal love]

I think your wah pedal is trying to become an oscillator. Seriously, the only resistor I would change in value, is the q1 emitter resistor. You can change other resistors, but the ones I never touch on the two transistor version are the 22k, 1.5k, the two 470ks, 10k and 1k. I always use the  + or - 20% tolerance rule, when modifying resistors, liking even smaller changes.pl