It’s not apparent what game you’re talking about, but I went to your old threads and saw you own a Road Kings.
Just to help other pinsiders diagnose the issue.

What do the connectors look like on the power board? Specifically the lower right hand corner.

The power comes in through the yellow wires and goes through that relay and back out to those wires in the connector right next to. The ones matching the GI to the playfield. Test for current with it powered up and see if it makes it in from the yellow wires and back out to the GI wires. See where you are losing power.

Not for Gi, GI is AC. Hot to common not hot to ground.

Have you pulled GI fuse and checked with a meter ?

Bulbs good ?

LTG : )

Manual will have that information. Did you remove the fuses from the board and check with a meter ?

No. Hot to common for AC, not ground. Youtube or Google, study up on testing AC voltage.

LTG : )

To get a correct reading you need to touch both sides of the ac circuit with your dmm on ac. Look at the schematic to test. However if you do test to ground the reading will be off, but you should still see if there is current, but the test would be inconclusive if it was enough.

But yes, to test the fuses, pull at least 1 side from the holder and test for continuity.

On the transformer is a yellow plug. That burns as well at times causing a failure.

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.

So what was the problem... It's not respectful to ask for help and not review the resolution....

You just learned one of the most important tenets in pinball repair....with fuses...how they look and how they test in the holder is of zero value - remove one side and test....