This Belman Bass Guitar came in with a dead preamp.

The preamp is potted in an epoxy resin.

I remove the epoxy resin (very carefully) while drawing the circuit diagram on paper.

Then clean the pcb, ready for reassembly. 

I fit new components and wire.

And cover with heat shrink tubing (neat huh).

Then attach the wires to the pots, pickup and jack and test.