Your GI comes from the transformer in the form A/C as 2 wires being yellow & a yellow/white.

It then splits into 2 yellow and 2 yellow white wires and joins to the board at the bottom right hand corner in your picture which is the power supply board.

One yellow & yellow/white go to the relay above which is the blue rectangular cube and out at pins 6, 7 ,8 & 9 and the other yellow and yellow/white wires become your 5 AC pairs which are fused by the 4 fuse bank underneath.

these are seen at J8 next to where the GI came in as 4 wires.

white/violet & violet is one pair and white/yellow & yellow is one pair that do backbox or playfield, don't see it listed in schematics

white/green & green is one pair and white/brown & brown is one pair that do backbox or playfield, don't see it listed in schematics

white/yellow & yellow does 2 pairs,

so there is a total of 5 pairs to control the GI lighting, 1 would be for the coin door, 2 for the backbox and 2 for the playfield.

so to test for AC use the connector J8 which is a 9 pin connector with the 4 solid wires to the right and the 4 with tracers to the left, put one probe on say the brown and the other on the matching pair being brown/white, violet and violet/white etc.

as mentioned earlier, before any testing and with the power OFF, flip out one leg of each fuse and test for continuity.