The pop bumper lights are turned on and off by the I/Alternating relay which is driven by the F/00-90 relay. Every time 10 points are scored the F relay (AS mini stepper) should take one step and change the I/Alternating relay and pop bumper lights. Chances are good that your F relay isn't stepping reliably. If you're lucky it just needs a simple cleaning. If it needs more than that don't disassemble it until you've read up on it. There's lots of discussion here about the AS relay.

/Mark

Yeah it's possible it is working correctly except you not knowing that it's the alternating switch in that relay that 'flips' them.

Yes, but the stepper is triggered by the 1000s reel. Notice that if you hit a lit pop bumper 1000 is scored and the lights immediately go out.

Best way to test is trigger 1000 scores and see if the mini stepper advances. By the way, the stepper also changes the special targets once all cards have been hit.

You're right, although the F relay is labeled "00-90" relay it's driven by the L or 1000 point relay. It doesn't change every time 1000 points are scored though:
Top Card F relay (resized).jpg
During reset it is driven by pulses from the Score Motor 1A switch through another switch on the A/Reset relay for as long as reset takes. But during game play it is driven by the L/1000 point relay through the same Runout switch used to reset the 1000 point score reel. That means that the F relay fires and the pop bumper lights change when 1000 points are scored (L/1000 point relay fires) and the score reel isn't showing 0 (when the Runout switch is open).

I hadn't seen this before but it's another way to randomize the match calculation which is also driven by the F relay.

Thanks for pointing that out, Mark - that's a pretty clever way to randomize the match function.

That matches the behavior of our machine. It’s not “truly” random, but it appears to be as your score rolls along.

The ace allows the center pop to light for 1000 points. All the left targets allows the left pop to light, hitting all the right targets enables the right pop.

Dave