Hey All-
I am in the process of updating my 1972 Fireball Pinball Machine (just took out of storage). It fired up for the most part, after sitting for 20+ years. One of the flippers wasn't working initially, spent some time on that and is functioning as it should. Now the focus is the GI lights for the back glass - nothing is lit up on the back glass. Any ideas? Appreciate any insight anyone may have.

Thank you all for your advice. The update is it is working as it should. I cleaned the jones plugs and gently took out the fuses then put them back in and it worked! Between those two items it fixed the problem. Thank you all the feedback - greatly appreciated.