Built 3 Muffs....2 have no sound/no LED

[Jonny toetags]

I built 3 muffs using the GGG schematic.
2 out of the 3 have no sound and the LED doesn't work.
All 3 are wired the same, all 3 boards are identical.
What's the chance that 2 out of 3 footswitches are dead?
Just looking for some troubleshooting techniques before I have to start pulling the pedals apart.

[R.G.]

I built 3 muffs using the GGG schematic.
2 out of the 3 have no sound and the LED doesn't work.
All 3 are wired the same, all 3 boards are identical.

Did you build them all at the same time, or one after the other?
Where did you get the boards?
PCB or perfboard or Vero?
Parts from the same lot? Or ordered at way different times?

What's the chance that 2 out of 3 footswitches are dead?

That was what a couple of the preceding questions were about. If they were from the same batch, chances are better than if they were from different batches or different manufacturers.

Just looking for some troubleshooting techniques before I have to start pulling the pedals apart.

Well, all three were made by the same technician, right?

I'd tell you go to to diystompboxes.com's build-your-own-stompbox forum and read "Debugging: what to do when it doesn't work" but it's down right now.

The bottom line is that you have to gather enough information to make good quesses about what is wrong. Do not be seduced by thinking that both non-functioning ones have the same problem, although that is possible, or that the nominally working one is working right.

The general outline for debugging is to
1. Verify that power is both correct voltage and getting to the board properly. Do this with your multimeter at the power source (battery or power-in jack) AND on the board. Do not assume that because you can see a wire or trace between points that the wire or trace actually connects. Bad solder joints are too easy to make. Measure at the power source to verify that good power is even possible, and then on the circuit board to verify that it's getting there.
2. Measure the DC voltage to ground on each pin of each active device. Do not assume that "if this is OK, then this other thing is OK." Measure, and write it down.
3. Evaluate what you have. An NPN must have the following conditions true to amplify and pass signal:
a. emitter at lowest voltage of the three pins
b. base 0.45 to 0.7V higher than the emitter
c. collector higher still than the base; generally you want the collector-emitter to be something roughly like half the power supply.

If these conditions are not true, it CAN'T amplify. Once you find this out, you can continue with looking at AC signal passing through the circuit.