Last time I worked on a GI, it also had opto issues similar to yours, but not exactly the same. The game was showing a credit dot and a switch 77 error. I ended up doing a few things at the same time, but I don't know which one ended up fixing the issue.

I replaced that island opto board. (Sadly, these seem to be unobtanium these days.)

I used electrical tape to extend down the opto interruptors to make sure there wasn't light still able to slide under them.

I sent away the power driver board for repair to @borygard.

My guess is either the opto in yours has gone flaky, or the PDB has some issues. After looking at the schematic, there are a couple chips on there that are labeled "Opto Isolators" at U7 and U8 that might be at issue. I just wish I had kept a copy of the full list of repairs Rob made to that board. I gave it to the customer.

That board is tiny and can be easily reproduced. They are also easily repaired. It's possible the transmitter side of the slotted opto has failed if the switch does not open or close.

Those ICs are used to detect the flipper cabinet buttons. That is their only purpose.

Even though the flipper switches in GI are leafs and not optos? I didn't think optos were used for flipper switches until Fliptronics II setups, is that right?

I sent the PDB in to Borygard because there were plenty of other hacks that had been done to it and I knew he'd be able to clean them all up and make it right, which he did. Wether or not what he did on that board helped with the flaky island opto, I don't know for certain. At the time I replaced that island opto board, they were only like $35 or so. So it was cheap insurance to just go ahead and get it.

This was many years ago and I haven't heard back from the guy at all so I assume everything is still working fine.

Yes. With pre-fliptonic (non-fliptronic) machines, the optoisolator (not slotted opto) acts like a "relay" between the +50VDC circuit and the switch matrix. When there is current flowing the transmitter side of the opto starts transmitting. The receiver side is connected to the switch matrix.

w89_pdb_u7_u8.jpg

With fliptronic machines, the cabinet button may be either a leaf or a slotted opto. The switch is low voltage and in fliptronic machines, are part of the 8x fliptronic (direct grounded) switches that are detected on the Fliptronics board. These fliptronic switches are NOT part of the switch matrix.

Probably a "basement" board then. Without images, it's all supposition.

Don't replace parts unless they are proven to be bad. You can cause more damage to the board than you are fixing. This does depend on your skill and experience level but, in general, most hobbyists are not board repair technicians. I have seen more damage done to boards from attempts to fix a board than actual fixes of problems on boards.

If it was working before and it now longer working, it is likely you have wired or connected something incorrectly. With optos, it may also be positional (mechanical). Check the switch registers correctly in the switch edge test (T.1) and manually block (interrupt) and unblock the slotted opto. If it works electrically, there's no reason to replace it and your problem is likely mechanical.

This is why when I was checking the one I was working on, I used the electrical tape to extend the interruptors down a bit to eliminate that as a possible cause. It could be on yours that when you put it back together, something didn't get aligned properly and the wheel, and subsequently the interruptors, aren't sitting down far enough to break the opto beam completely. So, I'd be checking all that first.