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What are you using for a power supply? Try a battery clip soldered to a power jack and see if you still get squealing. Some power supplies have enough noise in the power to do this - especially with high gain pedals. A battery will be pure DC though.

The wiring in the documentation is correct. You shouldn't be using a TRS cable, you need a regular mono guitar cable. Tip goes to the input of the board, ring goes to the black wire of the battery snap, and the shield connection goes to the board ground pad. That way inserting a cable into...

If you are looking at parts of the circuit that are unique to -1, then on the schematic you are basically looking at R11 through Q2, IC 1.2 and through to IC2.2 I think. I am a bit hazy on it, but I think the purpose of that network is basically to buffer and filter what starts out as a square...

So, with level and drive all the way down you still get the tone? What happens with level down, drive down and then shift the mix from side to side?

Also, where did you get your J201s? They are notorious for being faked in TO92 packaging

Don't go swapping out parts until there is some idea what the problem is. Does the oscillation occur at all settings of all controls or is it selective?

It sounds like a capacitor is charging up and when it gets to full charge it is stopping the power supply. I would be checking the power supply caps - for orientation, for the correct value and also to make sure they aren't shorted to somewhere they shouldn't be. Also it might be useful to...

I could be a bit wrong about my understanding, but my understanding of an op amp is that it works by sending a signal out the output that will make both the inputs the same. That is why you need a feedback loop back to the input. In this case one of the inputs is grounded, so the output will...

I plug an old MP3 player into the input jack using a 3.5mm to 3.5mm cable (standard MP3 player or phone audio cable) and a 3.5mm to 6.35mm converter. Just play a few of your favourite songs. You are really mostly listening to see if you have signal at first, rather than what the pedal is doing...

If you measure that the correct lugs are connected in each position, and that there are no lugs connected that shouldn't be, then your switch is OK. What you said about connections in post 3 is not correct though. This is what to look for The switch board may also connect some of the lugs...

Measure voltages to the op amp, FV1 and EEPROM

2n7000s and a single 1n34a is exactly what I used for clipping in my ADHD pedal. The arrangement is a bit different (clipping to ground rather than op amp feedback loop) but it sjhould still work.

Q4. The emitter voltage you measured is higher than the base voltage. If that is correct then I think that will turn off that transistor. I would be looking at the component values around those legs to see if you may have the wrong value there somewhere

Looking at the board, the round pad is connected to the ground plane, so that is the -ve terminal of C10, which I think means you have it correct

If your DM doesn't have a continuity test you can do the same thing with a low ohms range. somewhere between 0 and a few ohms reading would indicate continuity. I would definitely test the switch before trying to remove it. Test that the lugs that are supposed to connect in each position do...

The schematic shows lug 1 of the volume pot going to ground. The PCB had the square pad going to ground, so lug seems to be the square pad. The pinouts of 5457s and J201s are the same, so that shouldn't be a problem. It does sound like a ground issue. With power off and one multimeter...

OK, usual Q's. What are the voltages on your op amp pins? Have you got an audio probe?

That is a reputable source. They almost certainly are what they say they are

The traces are so hard to see on a black board (probably deliberately I suspect). Anyway, just to change topics, where did you get your J201s? Most of the TO92 ones currently available are fake. At least one connects directly to 9V. A fake one could potentially muck around the voltages maybe?

OK, I have one of these boards unpopulated. It looks as if the trace for pins 1 and 8 of IC100 comes from one end of R18. Check and see if one end of R18 has 9V, and also check for continuity from that end of R18 to Pins 1 and 8 of IC100