Is there a way to check this jumper wire to verify that it is operational. I am assuming using the DMM on ohms to do a continuity check from one end of the wire to the other. If I see “resistance” in the form of Ohms does that tell me that the wire is installed properly? Thanks

If you see no resistance the jumper is not broken internally. Post a picture of the back of the board.

Here is the back of the SBU and the VSU

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Hard to see at that resolution- does it match the picture in post #59?. Mine is a later revision without jumper.
It should connect J3-5 and the top of C14. This can be verified with your meter on continuity or resistance (ohms).

Not sure if I am testing it right b/c I put the DMM on ohms (levels between 200 and 200k). I put one end on J3-5 and the other on the top of C14. The DMM is automatically at 1 with no contact. When contact is made, it reads at some number e.g. 12 on level 20k, and then goes down to 0 and stays there.

Here are close ups:

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Looks correct. Typically an IC chip goes bad and needs replaced. The purpose of the logic probe is to determine which one.

I got the logic probe, and started probing around the IC’s with the pin in attract mode, and just noted the signal, I.e. high, low, or pulse. With this information alone, would I be able to determine anything useful? One thing that I noted, for example, is that of all the pins on the IC’s only one results in a “sound” when contact is made with the logic probe (which is like a hum/buzz of sorts). Does that mean anything useful? Thanks

Some probing is done during booting but most during the solenoid test when the game runs through speech test. Do you have the manual? Look at the testing process referenced at the start of this post and the thread I linked in post #97. That should give you a place to start.

And it was right there, right under my nose, all along. Went to probe this pin, but noticed that it wasn’t there? Went to my notes from these threads, and I had a note that MPUJ4-11 should go to VSU J3-5. But, on my pin it looks like VSU J3-5 is going to MPU J4-9. I moved the wire from J4-9 to J4-11, and “one, two, three” etc. !!!

So i am posting the before and after photos. It reminds me of a concept I like very much: Sometimes a small change can make a big difference.”

Thank you to everyone for all your input.

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And so the back glass finally goes back on.

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I wanted to go into the schematic to confirm the MPU J4-11 pin function, but am seeing “NU”. Is that a mistake in the schematic?

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Sterns wiring diagrams are just generic - they didn't update them per game and forgot to add that speech signal function :-/
The MPU board schematic even has two connections for J4-11 and one of them is wrong.
J4 pin 11 on the top left of the MPU board schematic should be J4-13, not J4-11

J4 pin 11 on the bottom right of the MPU board schematic is correct and where the speech busy signal goes.