Washburn B30 (ABT) knob functions

[wesg]

Hi, All!

I am fixing a Washburn bass, I'm 99% sure it is a B30, with active pickups for a friend of mine.

The bass came to me with two broken pots; one was in pieces, and it turns out the other one has internal damage (the track board is in two pieces inside). I have replaced the pot that was in pieces, but I have not replaced the other, which is the push-pull pot on this bass.

Can anybody tell me what the push-pull pot in this bass is supposed to do? I am having a very hard time sourcing a correct replacement and want to offer some other options instead.

What's strange is that it only has three terminals, so I'm thinking that maybe when it's pulled it is out of circuit?

Replacing the pots on this circuit board is a giant PITA if you want to keep the bass stock. For anybody out there searching this forum in the future, they have a 6x25mm shaft with an M7x0.75P thread on the bushing on a 17mm pot body. The dimensions are critical if you want to keep the same mounting hardware. There is not enough material to re-tap to a 3/8" UNC bushing.

Thanks,
Wes

[wesg]

Just to follow up my own post, this bass is working properly now. It turns out the mystery push-pull pot was not a push pull pot at all ...it was merely a broken pot!

Here's a full explanation of the knob functions - (Pardon the lousy playing, I'm a keyboard guy): https://www.youtube.com/watch?v=fpjKFYOARDk

If anybody else working on one of these is using the B30 schematic on the vintage washburn site, it seems to be pretty close, but it is definitely not the same as this guitar, or the other B30 I've seen. The pots are different values and the guitars do not have any switches; also, there are fewer wires from the pickups. I *think* the schematic is for a different pickup which could also run in passive mode. But it was close enough, anyhow, to help me track down the micro-crack in the PCB I had to repair.