The 120vac on the PSR is converted to +_ 18 vDC and + 10 VDC from the PSR and goes to each drive for board logic ( daisy chain ). If you don't have any lights on the axis drives you need to look at the DC voltages.
On the spindle drive plug C4 pin 5 is + 18 vdc, pin 6 is - 18vdc, pin8 is +10vdc and pin 7 is common. Pin 1 and 2 is 120 VAC
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