Out of curiosity. What causes lights in the backbox of older pinball machines to flicker when the flippers are pressed?
I'm quite sure it's a normal thing for older games to do that. It happens on my 1979 Magic. It's not a issue as you don't realize unless you're looking.
The backbox, GI, and under the playfield have all been switched to LEDs. I'm using the siegecraft boards so I could put LEDs into it to save power draw.
It is only the back box that does the very quick flicker with each flip.