LED 6 is lit in your pictures.

LED 5 -a little higher- will go ON when coindoor is closed

It is a 40KHz pulsing LED. Taking Voltage from it will give no correct value.

Yes, but that is depending on the camera. Newer ones can have IR-filter.

Check other -working- opto with camera to see if it shows IR-light on display.

The opto on mini-playfield is driven by a 24-opto-board under the playfield. Is its LED lit ? Are all 3 connectors in place ? Did you check it in switch test ?

Could be a broken leg of the ir-LED on mini-playfield,.. or a leaking capacitor on the 24-optoboard.

That is because the receiver wants a 40KHz signal.

Maybe the WHT-BLU wire got shorted with a power-line when it got loose from the standup target sw #56
This same wire goes to the 24"-opto-board and could have blown the optocoupler (U2) on this board.

Excellent !!

That would have been my other hobby when there was no pinball : )

Thanks Chris,

The Blue-White wire was from the beginning suspect for causing the troubles in the sw-matrix.
Lucky the 24" opto board has an opto-coupler so no further damage on this board.

Nice picture you have there.

It looks like this is about "hurricane" so the picture suites the correct board now.

What stands out immediately on the display with sw-matrix is that not only the rows 1,2,6,7 are closed, but also direct switch D1 and D2.

Are D1 and D2 still active when J205 is unplugged ? If so, I would agree by bssbllr to give the ASIC a gentle push into socket.

And with machine OFF, check all inputs and outputs of the LM339's for a short to GND with multimeter.
LM339 inputs in that great picture are in CYAN color, outputs are in PINK

I grew up with WPC
55 dunk the dummy.jpg

I think the LM339's lost continity with some signals/supply.
Measure continuity for all 5V, GND and data signals on the LM339 chips with the picture you used in post #49

https://pinside.com/pinball/forum/topic/wpc-89-cpu-board-info#post-3570794

Go to this post and scroll down to the animation on the bottom of this post. The voltages found in this animation are valid for all switch inputs (J205/J208/J209) as long you are feeding the inputs with GND.

Take your multimeter and start measuring the voltages at the outputs of all lm339s. That is pin 1,2,13,14. Then you know at least in what direction to search.

The fact that you have multiple rows being LOW without the lm339's installed, makes me think that the 10K pull-up resistors are not making contact with the outputs or 5V.

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again:

That is partly correct.

U18-1 is floating or input at U18-8 is not pulled HIGH or U18-6 is not 5V

For the other ROWs, next stop will be the inputs of U13 . For direct sw. the same for U15.
U13 and U15 pin 2, 4, 6, 8, 11, 13, 15, 17 should be 5 Volt. (on bench with no connectors on inputs)

If not,then the board misses traces or pull-up resistors.