Has anyone experienced this symptom with a build

[JPB]

Hello All,

I recently breadboarded and then built a circuit into a pedal. It's a simple overdrive with a 4558 chip (which I installed on a socket). The symptom is that when i turn on the pedal (either connected to battery or adaptor) the guitar signal disappears, and I get a heartbeat type of sound that actually speeds up or slows down when I turn the volume pot (100k audio taper). Turning the gain pot (10K linear) does nothing.

Has anyone experienced this before and what might it point to?

Thanks, Paul

[JPB]

Also, the circuit sounded great on the breadboard. So I'm thinking the problem either lies in the off-board wiring, or my layout on the pc board?

Thanks, Paul

[Paul Marossy]

Sounds like it is "motorboating", albeit very slowly. I'm not sure what would be causing that. All I can suggest is doing the usual troubleshooting stuff and looking for any mistakes that you might have made.

[slacker]

You can sometimes get that sort of thing if your input and output jacks aren't grounded.

[JPB]

Thanks folks,

I'll check my grounds to the jacks again. I've just looked at the board under a magnifier and I don't see any solder bridges or anything out of the ordinary.

JPB

[jambers]

Maybe an elco that's been reversed?

I've had an issue like that with a bad (read old and used many times) potentiometer once. One lug inside was broken, which was the ground connection. Changing it made it work like a charm.

[dschwartz]

i recently had that issue.. it turned my overdrive into a tremolo-ring modulator as i turn the gain pot..

i ended up changing the design and didn´t spend much time debugging that behaviour, but i´m pretty sure it has something to do with shorting the output of the opamp to ground or vref, making it see a low resistance load..it was weird.. but funny

[oldrocker]

If you audio probe your circuit it will be easier to track down.  When the signal cuts off you look around that area for solder bridges, errors or part orientation issues.  (AUDIO PROBE) the best debug tool for fixing stompboxes.

[liquids]

Sounds vaguely familiar....make sure the input and output connections aren't reversed? 

Moreso I'm with oldrocker - check the voltages at the chip, and if that is sensible, audio probe.