BBE Mindbender expression output ticking problem

Frequent questions about dead or faulty pedals. Whether you repair, mod or build pedals, debugging is important. Threads about general debugging problems irrespective of the circuit involved...
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Joined: 11 Jul 2013, 14:40

Post by drwasabi »

I've been attempting to add an expression pedal output to adjust the modulation rate of a BBE Mindbender (true vibrato/chorus).I used a switched TRS jack socket between the board and the pot, and unshielded cable. The rate pot is situated at the opposite end of the pedal to the new socket, so the wiring runs the length of the board, and back.

Everything works OK when the pedal is in a disassembled state, with the new jack and wiring stetched out away from the board, but when packed into the pedal enclosure (or even just bringing the new wiring closer to the board) there is bad interference which "ticks" at the rate of the modulation, regardless of whether the effect is on or off, or whether the expression pedal is plugged in.

Could the solution be shielded cable? A cap to ground somewhere? Both?

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