Making an eq bypass

Like this: http://www.sadowsky.com/media/pdf/wiring_diagrams/VintTone_retrofit.pdf

Where the blue wire is the preamp input, the green is the preamp output and the black is the one coming from the passive part of the circuit (what currently goes into the preamp input).

 

Sorry about the late reply, I hadn't seen yours till now.

You can use a Push/Pull pot if you find one of the same value as your volume pot. If not, you can use a mini toggle switch. This would be the wiring:



Note that I've drawn it like that for clarity but if you were using a Push/Pull it would be upside down on the picture, i.e. "up" would be active and "down" would be passive.

Also, I'm assuming that, of the two wires that go from the balance pot PCB to the middle pot PCB, the top one is hot and the bottom one is ground. If it's the other way round, swap the connections in both PCBs accordingly.