Back from the festival. Man oh man, Luke Doucet knows what a Gretsch is for.
But, on the topic. Thanks for the gutshot Dave. It's clearly a standard 3PDT switch, used exactly as I might use it. Don't make too much of the little board it comes on. A number of places sell those little boards, as a way of easing the installation of switches, using ribbon cable.
Officially, those switches are break-before-make, which means there will always be a brief moment where the pedal circuit, and switch, is disconnected from what comes before and after it.
Assuming the source of the pop is not within the pedal itself, the question for me then becomes "Is there anything it might be plugged into or that plugs into it, that might have an unterminated capacitor?". Again, that assumes that the PAL 959 itself has its input and output capacitors properly terminated with a resistor, so they can bleed off any residual charge to ground.
The fact that the pop occurs when you engage it, but not disengaging, and that it seems independent of the amp used, suggest that the pedal itself might have a "floating" input cap. The maker/s seem to have gone to a fair amount of trouble to make a decent product, so I'm reluctant to assume they have such a floating cap. That said, if you have the gear and confidence, you can try the following.
There are a few ways to wire up a 3PDT switch for true bypass, but the most commonly used is this one below.
- use a meter to identify which of the switch pins/lugs takes the signal from the input jack, and which two switch lugs are directly connected to each other as per the "link". That will help you to identify which switch lug is the one that goes to the input of the circuit without having to take the whole damn thing apart (and chase the stupid washer that fell out and rolled under the bench). If you can, temporarily solder a 1M resistor (or even 470k, if push comes to shove) from that
circuit-input lug to ground.
IF it was an unterminated input that is causing the popping, then that would cure it. And if the problem lies elsewhere, then you can simply remove that added resistor, and go back to square one. Naturally, if you have wires with alligator clips, then I'm sure you'd prefer to "install" the added resistor with those, and leave the board pristine.
I'll await your feedback, and we can take it from there.