This exact thing is happening to me too. All four switches test fine in switch edge test, and the solenoid for resetting the targets is working fine too.

It works fine at first and resets the target bank after each hit. Then, seemingly randomly, it tries to reset the targets 6 times before the VUK kicks the ball up there. Then the targets fall and never reset again.

I reflowed the connector and optos on the drop target bank PCB, but still no luck.

Any help would be greatly appreciated!

Ok, I think I figured out what is wrong. When I close the "Popper" switch (#68) and either the "Lockup Right" switch (#63) or "Lockup Middle" (#64), it opens up switch "Mini Drop Right" (#88).

So, once a ball is locked in #68 or #69 and another ball is in the Popper, the game sees an open switch on the far right drop target.

I replaced the diode on #68, #63 and #64, but the issue still occurs. I am terrible at diagnosing switch matrix issues, so can someone let me know if there is a switch that is at fault and needs a new diode?

Thanks!!
Matt

switch_matrix_(resized).PNG

You might try cleaning the optos, you can normally get a q-tip soaked in alcohol in enough to clean them. If that doesn't work, they probably need to be replaced.

Good luck,
Dan

I cleaned the optos with a q-tip and alcohol and it didn't do anything.

I suspect there is another switch outside of the ones I mentioned that has a bad diode. I just don't know which one.

Take a look at switch 84. It's a standup target. Make sure the switch is wired correctly, and none of the solder lugs or diode leads are touching what they shouldn't.

Here's a reference portfolio.
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Switch_Wiring
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Chris Hibler - CARGPB #31
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Do all drop targets fall easily to the bottom? Or is there some gunk in there that prevent the falling seamlessly? Are you getting errors in the test menu?

My bet is that one of the four targets in the back is not falling when hit, and after about 30 games, the machine thinks the battlefield is broken and won't reset the four drops.

Thanks Chris. I had thought it might be that switch, but it was wired correctly and not touching anything. I replaced the diode, and that didn't seem to be the issue.

Everything in the drop target bank was rebuilt with NOS parts a week ago, so everything mechanical is working perfect.

This is absolutely something to do with either the switch matrix, opto board or CPU.

I tried swapping in a new opto board and CPU board, but no luck.

This is driving me a little crazy. Any ideas on what else to try to diagnose this issue before I start replacing every diode in the whole switch matrix? Uggg....

Check the connector going to the bottom of the mini pf, make sure all the wires in it are seated.

I tired re-seating that connector, but no change.

A switch matrix problem =requires= three switches to be closed.
It's not possible for a "ghost" switch to close without at least three switches being closed.
Perhaps you can start with all switches open. I know...optos will present a special challenge. And, switch 24 is always closed.
Then close switches one at a time to see when the issue manifests.
It would sure be easier with one of these fancy testers...
http://www.pinitech.com/products/64switch_tester.php
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Chris Hibler - CARGPB #31
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The reason I told you that is when I shopped my game I took the mini pf out to be able to clean and re-rubber the game. After I put everything back the back drop targets stopped resetting. I tried troubleshooting it but couldn't figure it out. I took it off and rechecked all the wires and found a few of them loose in the connector, I reseated them and they started working again. Now with that said if you reseated the connector and nothing changed then it's safe to assume the issue is elsewhere. I bet there are other errors that you are not seeing. Take the glass off and hit every ramp, orbit and switch with a ball (don't use your hand, your hand has much more force) and see if everything else is normal except for the mini drops. Report back.

I have one of those in a box, but I got the unassembled version.

Guess this is a good time to build it.

Doesn't using that tester just going to replace the switch matrix under the playfield? How do you use it to diagnose a bad matrix?

O. You're right. I wasn't thinking straight there.
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I opened all of the switches (except switch #24) by unplugged every switch under the playfield that can be unplugged and unplugging the trough. No change.

Here is what I am seeing with ONLY #24 and #88 (the ghost switch) closed.

- If I close #68 and #64, #88 opens
OR
- If I close #68 and #63, #88 opens

I built the matrix switch tester (fun build!) and was able to verify that I am able to eliminate the problem when the playfield matrix is replaced with the tester, so it isn't on the CPU board.

I tested the voltage going into the drop target opto PCB and it was around 14.7V, which seems high for what should be a 12V supply. Not sure that matters.

I have replaced the diodes on the drop target PCB, and #63, #64, #65.

I can provide a video of the testing that helps.

Well, after a few hours I narrowed it down to #68. The wire was soldered on the wrong lug on the switch and causing issue.

The previous issue works now. Thanks everyone for your help!

Nice work!
I bet when you noticed the incorrect connection, your brain went, "oh".
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