Crap I'm too late! The MPU needs -12V (coils could lock on if that is weak or not present). The flipper coils, pop bumpers, sling shots are independent of the MPU and driver board so there is a very good reason they will all work just fine. If work was done on the pop bumpers re-assembly is tricky, under no circumstances can the leaf that supplies the 24V to the coil be in contact with the other leaf switch on the same assembly which supplies the signal to the MPU that a point is to be given (Chip Z8 I believe it is will fry, if your lucky that's all).
The Power board is not entirely original, Cap C1 was replaced from it's original 2900uF, as well a radial was installed on C2 (3) instead of the original axial. I refurbish those www.pinheads-pinball.com I offer a kit (it's a crappy website I know so don't comment on that lol)
At any rate please, PLEASE do no throw the old boards away. keep them in the cabinet or ship them out for repair. Coin-op Cauldron is my choice if it's over my head, Clive is fast and reasonable.