Aria SB-1000 bass
This had all the usual problems: Open circuit pickup and dead preamp electronics. Furthermore, the internal wiring was a mess. A replacement pickup was ordered from Armstrong pickups ( http://www.armstrongpickups.co.uk) and the potted preamp was reverse engineered to see what was inside. In the end this was a very simple unity gain buffer amplifier that also generated its own 'earth' signal that is connected to the back of each pot. the screen of the pickup wire, and the earth wire to the bridge. The schematic for this can be downloaded below.
The wiring of the SB-1000
Notes from reverse engineering the potted preamp. Note that the opamp is drawn in reverse on this schematic.
The replacement built up on stripboard prior to potting.
Download the schematic here