Trying to break down the issues I have left to fix on Party Zone. One of which is a switch problem. Noticed that when playing, the switch for the back ball popper closes, it sends the Captain B Zarr head into a clockwise spin until the wires bind it up and the game shuts it down.

So checking the switch matrix in switch edge test here's what I found. With all three of the Head Optos CLOSED, closing switch 41 which is the back ball popper, subsequently OPENS switch 51 which is the Head Opto 1.

I checked all other switches in the adjacent rows and columns, and found that the left jet bumper switch 43 when closed, also OPENS it's adjacent switch; Head opto 3 (switch 53).

Normally I'm used to working with a phantom switch closure, not one that opens a normally closed switch. But obviously something is amiss here.

Just to be sure I checked the Row 2 switch 42 right ball popper to see if closing it would open it's adjacent switch Head opto 2, and it did not do so.

I've checked all diodes related to these switches, replaced the single diode that is on the head opto board, and still no change.

Any ideas guys?

Ok Lloyd, so if that's the case, then the typical scenario suggests that there's a diode shorted somewhere within the "box" formed by the switches involved....

Two of the switches are optos, so no diode there,

And I've replaced the diodes on the other two switches, (and checked the wiring, it's correct). But no change. Any further advice on how to pinpoint the issue surrounding this matrix problem?

Thanks

Thanks Lloyd, figured it out. Turns out the new optos installed, were of the wrong spec, even though sourced with the correct Williams part number. New optos, and no more faulty switch behavior. Game working 100% now!