Did you check all of the fuses? Lights run off 6V. Game mechs run of a higher voltage.

Do you have the schematic? There could be a switch controlling the GI lights. Good amount of documentation is available on IPDB.

Schematic at https://www.ipdb.org/files/2803/Bally_1975_Wizard_Schematic.jpg

There's a switch on the Lock relay that controls the lights.

Check the lock relay switch with the blue/red wire and blue wire. The switch should be in the closed position when you start up a new game. Make sure the switch is clean and adjusted properly.

That’s the switch on the lock relay that controls GI. The one above is the backbox.

4F85F88E-4A07-4383-BB71-30B1EC2A53E1 (resized).jpeg

You'll need to confirm with a multimeter if there is 6 volt power at the lock relay switch with the blue/red wire. If power is at the blue/red wire, then check the other side of the switch with the blue wire. Is there 6 volt power when the switch is closed at the blue wire?

I would bet a bad fuse holder. Happens all the time on Bally EM's of that era.

The bane of EMs is the switch that looks like it is making but isn't, and vice versa.

Clean and adjust the switches and if you still get no GI lights jumper the fuse and see what that does. Bally fuse blocks do have a reputation although I've never had issues with them.

I picked up a set of fuse holders at my local auto parts store. It was a set of of 4 that could be broken apart. I ended up using two on my Wizard! as well. This one is made by Littlefuse.

IMG_3916[1] (resized).JPG