Have an interesting(*) issue with a Sys 3 game. Here's what's happening -
The board seems to be driving things(*) in slow-motion.
To the naked eye, all bulbs look dim - even flashers. (Not JUST controlled lamps..) I can NOT put LEDs in - even non-ghosting bulbs will strobe horribly, the pulsing of the columns are so slow.
Perhaps once every three games, the game will 'miss' a switch activation. And it's different switches - not the same one.

Things I've ruled out, checked:
I've checked all lamp diodes - all report good on DMM.
I've swapped driver board; no change.
I've swapped CPU board; no change.
If I disconnect the lamps, it *seems* as if the game stops missing switches. (However, this is so random, it may be a red herring.)

Since this seems to be affecting flashlaps as well (perhaps coils, too?), and it happens regardless of driver or cpu board, it's gotta be something in the game. the game is my #nudge-it, which literally uses 33 lamps, 11 switches (including cabinet) and 8 coils (including the flash lamps). It's a *simple* game. I've been tempted to take the playfield out and plug it into my #bell-ringer cabinet, to see if the problem follows the playfield or not. (The two games share many of the switch/lamp lines, and coils are identical, save for one, so I'm not worried about frying anything.)

Any thoughts on what to check next?

You are correct, I haven't checked, and will need to do so. (I'm not a Gottlieb guy, so this is new territory for me.)
The ground mod has NOT been done, either. (In either game.)

Yup! Did check that -

But, it's not a rock-solid test, since the 'missing switch' happens to infrequently, that it's really hard to tell - after 'x' games and no switch misses.. was it because I t just normally didn't happen, or disconnecting the lamps actually 'fixed' it?
The interesting thing is that the flashers (coil driven) are running dim *as well*, and they don't 'brighten up' when I disconnect the lamp matrix from the driver board.

Awesome, thanks guys.
I know the issue - now I need to figure out why..

The 20v bridges in both games are getting 17.5vac in.
The good game voltage drop between the DC terminals of the bridge is 22.2vdc (give or take).
The game that's acting up, the voltage drop between the DC terminals is 14.5vdc.

The 33000mfd cap (the large one) is different between the two games.
The bad game has a 33000mfd, 15vdc(!!) cap, while the good game has 33000mfd 35vdc cap (and looks original).

Bad cap? (Guessing since the voltage of the bad game's cap is UNDER what the secondary should be sending, that could be the issue..)

Yup, looks like cap is bad, or at least at fault cuz of overvoltage.

Good game reports 53mVAC on the 20v feed.
Bad game reports 7.6VAC on the 20v feed.

Will order a new cap, and give that a shot.

Thanks again guys.

New cap arrived, I dropped it in. (Got a rather expensive one, at $25 a pop, that was 35v and screw-terminals.) Powered game up, and lamps were nice and bright - everything looked normal like the game next to it.

Got two small switching 5v power supplies for both games, will be installing them this weekend and going the ground mod.

I just noticed this for the first time last night. I knew plastic standoffs were used, but I always assumed there was ONE metal one for each board. Nope. Strange since they went out of their way to GROUND the foil-covered wood..

The pic is my new switching 5v supply to replace the old one, pretty happy how it turned out.

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