Davey, Spa-Quip SP500 (Spa Power 500) PCB. The PCB is a direct replacement for the SP500A15MK2 and SP500A20MK2. This PCB can also be used to replace all old style 500 PCB's as no other 500 PCB is still made. Wiring changes will be required on the following models. 54500-15, 54500-20, 500A15, 500A20.