Mr. Pinball Tip:

Early Bally Solenoid Driver/Voltage Regulator Board Test Points

TP1 = +5 VDC (upper right side)
TP2 = +190 VDC, Out to displays (upper left)
TP3 = +5 VDC (middle right edge)
TP4 = +230 VDC, In for displays (upper left, just next to TP2)
TP5 = 11.9 VDC (upper right side, just above TP1)
TP6 = Jump to base of driver transistor (Qn) to activate solenoid (lower right)
TP7 = Jump to base of transistor driver (Un) to deactivate energized solenoid (lower right edge)
GND = ground (center)

These test points also apply to Stern boards from the same period.
Acceptable tolerances are generally within 5-10%. Most voltages are usually on the high side. If TP2 is high it may prematurely burn out your displays. If TP2 is low, and your displays look bright and flicker-free, then your displays will likely last longer. If TP5 is on the low side the MPU may not boot.
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