OK, on to my next issue...

I have one display (the Player 2 display) on my Mr & Mrs Pac-Man that is displaying strange behavior. It displays a score based on whatever digit is in the "hundred-thousands" place across all digits. So for example, as you can see in the linked video, when the other player displays are showing "421,130" for HSTD, the Player 2 display shows "444,444."

In-game, if I have a score under 100,000 it displays nothing (effectively a "0" in the hundred-thousands place). If I have a score between 100,000 and 199,999 it displays "111,111." If I have a score between 200,000 and 299,999 it displays "222,222." Etc.

Any idea what might be causing this? I swapped the displays around a few times and the issue stays in the Player 2 position. So it's not a bad display. The wiring to the display appears correct, as does the wiring to the A4J1 and A3J3 connectors.

Thanks!

https://photos.app.goo.gl/Tnqemrbrkm7LSa2m6

I will give these things a look. I have an Alltek MPU, for what it's worth.

Here's a look at the display self test...everything looks normal (except no millions digit), not sure if the playfield strobing is normal.

https://photos.app.goo.gl/tuZgTXk25m3Do3s3A

I do have a fresh 6820 I can swap out to see if it helps. If not, I can put base a 5101 and see if that changes anything.

No change with the fresh 6820. For the 5101 at the Bally U8, I'm not sure if there is a viable replacement on the Alltek. The Bally U8 equivalent appears to be U15, where there is this:

PXL_20211127_192658369 (resized).jpg

Doesn't look like anything I can replace. Do I have that wrong about the Bally U8 being equivalent to Alltek U15?

The Bally U10 and U11 are the Alltek U6 and U2 on my version. Those are both newly-installed and working PIAs in this case, but i can give em a swap and see if it yields any changes.

I swapped the new PIAs, no change. I did swap in a different MPU and the display worked normally (though still no millions digit), so at least I can confirm something is up with this MPU. Though still unsure what.
PXL_20211128_135444374 (resized).jpg

I had a similar thought. Checked that wire (black and green wire from Position 12 on the displays to A4J1-7, if I read the schematic correctly) and everything looks in place, continuity from display to MPU tests good. Hmm.

Will give it another another look. Maybe I am missing something.

Any other thoughts what may be causing the failure of my seventh 'millions' across the displays? Feel like I'll start there

Thanks for helping me think through the logic. I will experiment and examine a bit more later tonight, but a quick test did yield some results:

- Removing pin 7 on J1 actually fixed the buggy digits on the player two display position. Still no millions digit (as expected).
- Removing pin 7 and replacing it with pin 6 yielded the same result, no difference. Still no millions digit.

Plugging pin 7 back in place made the displays brought the buggy digits issue back on player 2 display.

I will have to re-trace the wiring and see what I am missing.

Agree, I keep waiting to find a broken wire or something simple and go "d'oh!" So far no luck

I will start diving deeper looking for shorts, and see if that turns up anything. We'll get there! Thanks again for the thoughts.

I found the issue!

After narrowing it down to the wiring (I had re-pinned the display connectors and installed new Wolffpac LED displays), I was finally able to isolate the issue.

Turns out everything was re-pinned and re-installed properly. But...on the original display IDC connector housings, there were wires that were routed across some of the unused pins. So, for example, a given wire would be daisy-chained (but unused) across two connectors, say, to get to the third connector where it was used. The wire was still inserted into the IDC on the skipped-over displays, but on an unused pin. This didn't cause any trouble on the original displays. On the Wolffpac displays however, this appears to be an issue. At least it is in my game.

Removing the daisy-chained connections at unused pins and just letting them float freely cleared the issue, and the displays worked normally (fixing both the weird player 2 display issue and the missing 7th digit).

So I've cleaned them up and left the connectors that were on unused pins removed from the housings. Everything seems good.

Before I started messing with it, the wiring hadn't been messed with. It was "factory settings"