Check to see how the xformer is tapped. There is labels usually right nearby indicating settings. Maybe it is set for 110v.

Are you sure your meter is working correctly? If so i would go ahead and set it for 120v if you can easily change the pins around in the connector.

MPU TP3 should be half of what the 43v line which it basically is.

No 7th flash, make sure the R113 and R16 are not burned (they are probably okay if you correct at TP3)

Check IRQ line that goes from u9 CPU to both pias and look for a short or lack of continuity.

Try a new U10

Check to make sure zero crossing circuit at U14 is working correctly. Start at the PIA U10 P18 and look for a low pulse(i think bally says 1/4 vdc). If you are missing that work back wards towards u14. Bally was nice and wrote the voltages in the schematic in this section, follow through and check each one.

If you have a low pulse on the PIA zero crossing pin. In theory the zero crossing circuit should be working correctly. So i am kind of at a loss. I don't think the overvoltage on the 43v line is going to cause zero crossing not to work. Try disconnecting the sound board. The sound board uses the 43v line and it ramps up the voltage on its board. There is a blocking diode on the sound board that should not allow it to leak back into the 43v line, but it can fail.

Still double check u14. Look for low pulse at U14 P4 and P15. High pulse (inverse of prev) at P10, P14.

A bad PIA or socket should be caught by pia test flash #4, U10 is tested sans P18 for zero crossing during the 4th flash. A floating input/output from a bad socket wouldn't stop the 7th flash unless it is zero crossing CB1 line P18.

Maybe the MPU is not selecting U10 properly. I suppose U18 or U19 could cause your problem, but i would think unlikely. Check u18D for inverting signal. Check U19C and U19D. Looks like A7 involves chip select for u10.

CR3 on the sound board is probably shorted.

Happy i could help = )

Yay.

5101s are very sensative to static damage. A bad one sometimes slips past the power on self test and causes all sorts of odd issues.