This problem is so highly intermittent that my observations are rather limited. I've seen this maybe three times in the last few years. First the game was sitting in attract mode when I heard a soft clicking sound. It kind of sounded like the coin lockout coil, but it wasn't. The sound stopped before I figured out anything else. It happened again a few months later. Then it happened again while I was playing the game and this time I saw it was the #1 drop target coil. I thought that maybe the #1 switch was dirty, but that has nothing to do with it. When the game wants to drop a target, it fires the coil only once and doesn't care if the switch closes. The coil is attached to Q1. I poked around and couldn't get it to do anything odd. I tested Q1 and the associated resistors and diode. All readings were comparable to adjacent circuitry. If there is an intermittent circuit problem, I'd think the pulsing would be more random. The pulsing is steady. Maybe one pulse per second. It pulses for a few moments and then stops. And why would it pulse in attract mode?

I've had this game for ten years and this problem is relatively new. In early 2017 I installed an Alltek MPU due to battery corrosion. When I bought this game the battery was already cut away and the board looked clean. But over the years it started growing fuzz around the lower left corner and acting flaky. I don't recall if I ever saw this pulsing problem with the old MPU. The MPU connectors were re-pinned for the new Alltek board. Years ago I re-pinned the driver board connectors and replaced the header pins. I also did the usual driver board ground mods, but I haven't recapped anything.

I really don't want to shotgun this because the issue is so intermittent. I'd like to first figure out how to duplicate the problem. Any ideas? Thanks!

Bump for the weekend crowd...

Yup, same steady pulsing each of the three times I heard the sound.

No new information. I've been playing the game quite a bit over the last few weeks without indecent. And on several occasions I've set the drop targets and let the game sit in attract for a few hours. Each time I check back, the targets remain up.

Thanks for the replies...

I have messed around with the little white buttons, but I don't think that's the problem. For example, hitting the #1 button may drop the #1 target, but then that button is out of play until the bank resets. Likewise the buttons aren't in play during attract.

It's a click. No buzzing.

I don't have a spare driver board. I like the J4 idea. Given the periodic nature of the pulse, I'm thinking data. So pulling J4 could shed some light on that. Can the connector be pulled with the game powered on? I can't really do any experimenting until (if ever) the behavior reappears. Maybe a better idea would be to poke around the driver board's decoder with a logic probe.