1J11 connects to the solenoid drive transistors. Their function is to act as a switch to turn on ground for the solenoids and flash lamps, depending which of those is multiplexed by the A/C relay. That's all that is there between that connector and ground, just the transistors. Since all of them do not give a full brightness flash when operated normally through 1J11, but if you bypass them and ground it manually they flash at full brightness, I'd say you have a bad ground from the transistor emitters to the board ground, which is mostly obtained through the board mounting screws. You can verify this by using a meter to measure resistance from any of the associated drive transistors that switch through J11 (Q24,Q25 etc..) to ground. Make sure all your MPU board mounting screws are conductive and screwed down tight. You could also have a broken or scratched trace somewhere, maybe on the back of the MPU board.

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If you have verified a good ground (preferably with an ohmeter) then yes. I'd prefer to use a meter to locate the exact problem, but you can bypass the suspected fault temporarily. Jumper from a known good ground to the emitter of Q24, that should at least make that flasher (flash#4, whatever that is) and likely all of the flashers, work at full brightness if I am reading your problem correctly and bad ground is the problem. You might also see better performance from the solenoids that are multiplexed with these flashers if there is a bad ground.
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Is this still true? ground pin #5 of 1J11 - see if you have full brightness there.

Reinstall connector and ground the big tab on top of Q24, what do you have now?

OK, so basically we have attacked this circuit at both ends ground--->transistor and then transistor --->flasher All you have left is the transistor "switch". As long as they are the correct transistors and soldered properly, the only other thing I can think of is the duty cycle of the pulse fed to them from logic section is quicker than it should be. Are the flash bulbs dim in both game play and test mode?

Intriguing. Did this game ever work correctly in your possession? The reason this question is asked, if something has simply stopped functioning correctly it is *usually* easier to diagnose than something that has never worked correctly (possible parts changes etc...)

If I had nothing to go on, my next step would be to look at the input pulse train on those drive circuits and compare the pulse to a working game.

Another question: I assumed you are using standard incandescent lamps and that they are the correct ones. I don't think it will make much difference, but just poking what I can. Hoping someone has seen something like this before and might chime in suggestions.

Absolutely, that's easy enough to try. I am not familiar with software versions or changelogs for this title. At least swapping the software would rule that out. Sounds like it was a good buy.

Bah. OK. If I think of anything else, I'll let you know.

I believe there are different interconnect board resistors required for using the insert board flash lamps. Found this on the net:

So the ratings for a non-prototype machines, with no flashers in the backbox, appear to be:

R1 = 3 ohm
R2 = 4 ohm
R3 = 11 ohm
R4 = 11 ohm
R5 = 5.6 ohm
R6 = 11 ohm
R7 = 11 ohm
R8 = 4 ohm
R9 = 11 ohm

If your machine has flashers in the backbox, refer to the manual, as it appears to be correct for those machines.

Sounds like an upper level logic issue, perhaps a bad PIA if I had to make a wild guess. If they are socketed, easy to swap. Carefully touch them with your finger after the game has been on. They can be warm....but should not be so hot to cause you to pull your finger away, if so would be suspect. It can be difficult to troubleshoot a flaky MPU board without a hard failure .don't give up. At the price you paid, replacing the board is an option.

Might be a stupid question but is the ground wire from the lower cabinet connected to the stud with the wing nut in the head? Are all the green ground connector wires connected in the head?
The pic shows the head stripped out but the wing nut and ground connectors are there. This is from my old Rollergames.

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Yeah, I guess when you said all the boards look like new at the beginning of the thread it kind of threw me. Battery corrosion is insidious and creeps onto component bodies on nearly a microscopic level. Sometimes you really have to look carefully to spot it when an attempt was made to clean it without replacing components.

Did read it. Didn't see anything about ground strap or whether repairing the battery damage had fixed the problem. Thanks!

Great job troubleshooting!