Quoted from DumbAss:Well ... now you still do not have a definitive cause. The system you are looking at here is fairly simple.
The WHT-BRN (row 1) wire leaves the CPU board at J209-1.
It daisy chains (wired in parallel) to all the playfield switches in row 1. The order is not documented and varies between games with physical switch locations.
One of the points in the daisy chain is the 7-opto board at J3-5.
The corresponding column 6 wire is GRN-BLU and is connected at the 7-opto board in J3-12.
This wire is also daisy chained (wired in parallel) to all the playfield switches in column 6. The order is also not documented.
The GRN-BLU wire returns to the CPU board at J207-6.
There's not much more to it than that. The problem should be in one of two places.
The playfield wiring (either the row wire or the column wire).
The CPU board (logic ICs).
You can exclude the playfield column wire as the other switches in column 6 register. In fact, there should be a single GRN-BLU wire because column 6 only services the 7-opto board switches. Check ALL other switches in row 1 that are in the playfield (not cabinet). These are switches 31 (River "R2"), 41 (Light Lock Left), 51 (Left Sling) and 71 (Rapids Ramp Main). One of your images already shows switch 71 as closed.
The fact that switch 71 registers as closed indicates it is unlikely to be the CPU board. As previously you can exclude this by shorting J207-6 and J209-1 and then un-shorting it. This should cause the switch to register. You can short J209-1 to the other pins on J207 and each pin should register all the switches in row 1.
I'm afraid it's not going to be "this is where your problem is" because your presentation is atypical and you must do the searching and differentiation. Readers can only be guided by what you report as your findings and if you report your findings incorrectly that is going to be the basis for conclusion. I am not saying that your reporting is incorrect but rather trying to point out to other readers (or potential future posters) that reporting correct findings is super important. Reporting of findings is what other people use to make assessments and provide guidance.
Thanks again for helping me through.
!! We have solved the issue !!
I traced the white-brown (row) and green-blue (column) wires end-to-end and everything was connected and in place. After that, I started one by one unplugging molexed switches and re-booting the machine hoping that the auto-firing popper would not auto-fire with one unplugged (focusing the problem on the un-connected molexed switch). To mine but not
DumbAss 's surprise ... when I unplugged switch 71 and rebooted, all was silent. Found it!
If I had a keen eye, I would have possibly noticed (and understood) that switch 71 was closed on the T.1 test, erroneously. And that this might be the source of the issue. I did not, but in retrospect, it should have raised a red flag. I've learned something for next time!
So next, what is happening with switch 71? I took a peek and saw the issue...
PXL_20221007_203711364 (resized).jpg
A better look...
PXL_20221007_203827592 (resized).jpg
At some point, someone had replaced the switch or re-wired the switch incorrectly. Green/Blue wire should be in the middle.
I decided to just remake the whole little harness to be sure.
PXL_20221007_204714560 (resized).jpg
PXL_20221007_204720986 (resized).jpg
Reinstalled it and---viola!---no more locked-on popper.
So, what have I learned?
1) I've learned to break the system down into subsystems, and eliminate them in order to identify issues.
2) Pay closer attention to the T.1 test. If I had understood and inquired more about "Why is 71 closed"? I could have saved a lot of time.
3) Appreciate the national treasure that is
DumbAss . Willing to help, teach, and follow me (and you) down a troubleshooting rabbithole even though he has no earthly reason to care about me (us).
Thanks again!