The voltages at the test points can be found by looking at the sound board schematic for Silverball Mania on IPDB.
TP1 11.9 +-2.5VDC 0.1VAC
TP2 5+-2.5VDC
TP3 GND
The first three are the inputs from the power supply so these should definitely be checked. The other test points are for trying to troubleshoot the board with a multimeter, which can be done but it is much better to use a CRO. If U4 is faulty/suspect you will need someone with an EPROM burner to verify its contents. I have seen other Eproms go faulty due to wrong voltage being applied to them. Generally a faulty cap, resistor, diode on the sound board will not cause damage to the chips, the board will just not work. It is very unlikely these have failed and more than likely to be U1 chip + possibly others.
You could try to replace U1 first, then U2 and U10 borrowed from another Bally -35MPU. Failing that I would get U4 verified which I can help out if you get stuck.
regards Derek
