Unidentified circuit tone knob issue

[fitani]

Hello..
My friend has a 70s or 80s custom shop lefty PJ. It has EMG pickups with an active circuit Volume - Volume - Tone. He recently had some work done on the bass an after that the tone knob started active as a high pass in 1 direction and a low pass in the other. previously its was just a low pass. Pictures included below. Would be great if someone could identify the circuit and see if the wiring is correct. Red wires are connected to the battery.

Thank you

 

[dwizum]

Any chance there was ever a "before" photo of the circuit? It looks home made. Are there any components on the other side, or anything soldered to the pot?

There appears to be an SMT component missing - look two spots to the left of where the green wire is soldered to the board. It will be hard for us to know if that is on purpose, or if something got broken off - and if so, what. It could have been a cap or resistor that changed the function of the circuit.

 

[fitani]

Thanks dwizum. Will have to check what's soldered to the pot.

 

[dwizum]

If you wanted to get really in to this, that's a pretty simple circuit for a well known chip. You could draw a schematic by following the traces on the pcb and reverse engineer the design. Then it would be pretty simple to know what's missing.

 

[jbrew73]

Isn’t EMG and a model written on the bottom right corner of the first picture you posted?

 

[fitani]

Just saw that . Will have to open up the bass and check if it's legible. Thanks