i just successfully installed a 3PDT true-bypass switch in an MXR Phase 90 and a newer CryBaby What ... net up, the fuzz.

got my Fulltone 3PDT switch ready to go in. only info i could find on big muff mod's was for the older ones ... nothing on the late 90's reissue GREEN Big Muff Pi's (other than a schematic).

Anyone attempt this mod on this particular pedal? would this mod require similar steps as recommended with th late model CryBaby's? (severing the trace coming off the input tip, lifting a cap's leg and running a wire from it to the switch) .... or is it less involved than that?

any help would be greatly appreciated.
thanks,
m

If it's like older Big Muffs I've seen, it has a lead going from the tip of input jack to the board and another lead going from the tip to the switch.

You'll want to disconnect that input-to-board wire and hook that up to the switch instead.


And substitute the circuitboard input for "Send" and the circuitboard output for "Return" in this diagram (it's the same circuit whether you're making a standalone effects-loop box or true-bypassing a pedal)

Since you're using a 3PDT, you'll obviously be using the 3rd row of lugs to turn the LED on (hook the LED's flat side to ground and the round side to the middle lug of the switch, then hook a 1.5k resistor connected to +9v to the "on" lug of the switch, which would be bottom in this diagram).

thanks for the reply ... but, unfortunately this particular model isn't that simple. it will be a bit hard to explain so i am going to draw up diagram on it so i can get some help. basically, it's that i can't figure out which wires are the IN/OUT from the PCB. when i removed the old switch, i labeled each wire accordingly but there were a few that go directly to the 3 control POTS ... which i can't trace back to the PCB to figure out what they do. i don't know enough about this stuff to logically figure it out. i will have a .jpg of the original wiring available soon ... maybe someone will be able to help. thanks!
-m

There should be a wire connected to the second terminal of the volume pot (the middle one). Thats the output. As for the input, mine was connected to the inputjack and then the input jack was connected to the old switch. I have an older 70's version so it might be different. Other than telling you to look at the schematic and trace back to the input 39K resistor, I don't really know how to tell you how to find the input.

Before you get started, I think it might be the case that this pedal is already True Bypass. If you are looking for a light, then the Three pole is needed.

Do you have a digital meter, or can you disconnect the battery to see if I heard right?

If it is, then just copy the switch you have in place and add the light to the other single pole double pole part of the switch.

bb

You probably have the answer. Why is the question so hard?