Hi, Tech friends! I could use some help with a weird problem on my Junk Yard. I do have a manual, but I'm not great at diagnosing problems with modern games.
When I hit both flippers at the same time, it appears to trigger several of the opto switches. Specifically, I'll hit both flippers at the start of a game to cancel the intro animation and, before even launching the ball, the shooter lane opto registers a hit, the Alley opto registers a hit (causing DOG to advance) and the crane tunnel in the back registers a hit, scoring a sneak-in and advancing MULTIBALL. If I keep hitting both flippers together, MULTIBALL will advance, a multiball will start, balls will eject and keep shooting out and jackpots and super jackpots wil score on their own. It's insanity.
After a few days of poking around, I can report that:
1. There are no errors reported on boot-up.
2. A Single Switch test shows no problems - all the switches ( including the flippers) function normally in test mode.
3. All of the optos involved are on column 4 of the switch matrix.
4. To pinoint the problem, I tried disconnecting each switch (including the flippers) in turn and testing the game, but in each case all the other opto switches would go crazy like before.
5. There does appear to be some weirdness with the right flipper opto: in a multimeter test, pin 6 (+12V), which connects directly to the left flipper opto board, seems to be in circuit with pin 4 (ground) and, according to the diagrams that's not supposed to happen.
6. I've also checked all of the connectors, thinking that maybe on of them is plugged in backwards, but they're all keyed and they all seem to check out.
I've traced the problem through both flipper optos, the coin door board, the Power Driver and CPU boards and can't seem to find the point of contact that's causing a short circuit. I've also cleaned out as many opto lenses as I can reach.
In my experience, these kinds of issues tend to require tiny adjustments, rather than replacement of whole boards, but it's a matter of tracking down where the problem occurs. Maybe it could be as simple as installing a new right flipper opto?
Let me know if you have insight, if you have questions or can suggest any tests I should try. Your help is appreciated! Thanks in advance!