Hey All - working on a Last Action Hero, and ran into an annoying, intermittent coil issue. Hoping someone might be able to chime in with some advice.

Problem: Middle Scoop, Crane, and Shaker seem to struggle to work, or function intermittently.

Under test, the Crane will sometimes not move at all, other times it will seem to "pulse" and move slightly (maybe an inch) when the start (test) button is pressed. Similarly, the Middle Scoop will sometimes fire when the test button is pressed, other times it will do nothing, and on occasion it will attempt to fire, but only do so with maybe 10% power, barely moving the plunger. The Shaker (which I unplugged recently) was also struggling in test, either not moving, or barely turning maybe 1/4 to 1/2 a rotation.

As you can imagine, gameplay is basically impossible. The ball will often go into the scoop and stay there for quite a while before randomly being kicked out. It could be 10-15 seconds, a minute or more, or sometimes never. The crane will sometimes swing happily on its way, only to die randomly mid-swing. Other times it will move a fraction (like described above, maybe a half inch or inch each time the drops are all knocked down).

Crane switches seem fine, and sometimes the crane will actually work perfectly fine for a few moments (during gameplay). It's all very erratic.

I've been trying to check to see if there is a common wire or return for these three items, or something in the schematics that would link them. So far no luck. Anyone have any thoughts/advice?

Things Attempted So Far:

* The basics like reseating connectors, checking wires, etc.
* Verified the Middle Scoop coil is good. I swapped it with the wires to one of the pop bumpers (same coil type) and under test it worked perfectly, zero issues.
* Repinned the associated CN12 connector because I noted a tiny bit of corrosion on one or two of the connector pins. Also noticed that one of the transistors had a little corrosion on it. Seems to be "drip" corrosion overall in a few spots, rather than the kind that creeped all over the board like I've seen on some DE games.
* Checked connectivity/traces in areas I noted small bits of corrosion. Everything seems okay in that regard.

My next step was to test/replace the transistors, but I thought it best to see if anyone had any ideas first. It's the intermittent, erratic nature of this that's odd to me.

Thanks in advance for any help!

*Bump*

Anyone have a suggestion? Definitely a bit odd.

I wanted to circle back on this and close the thread, even though no one replied. Just in case anyone ever finds it and is curious what happened.

The small scattered corrosion was likely the culprit. I installed a replacement MPU and everything worked great, no issues that I can see. The original should be repairable, so it'll go in the parts pile for cleanup down the road.