Hello,
I'm cross posting from my Bobby Orr restoration thread.
Full description of the issue here:

https://pinside.com/pinball/forum/topic/bobby-orrs-power-play-from-scrapper-to-power-player/page/5#post-4154099

I copy-pasted here too:

"I'm having issues with the lights. Besides some of the sockets being flaky which I'll deal with later, I have the top bonus lights and the left and right lane rollovers not lighting up. In test, I checked whether the pins on the light driver socket were giving any voltage, but they're dead.
I tried swapping the board with a known good and I get the same thing.

I'm thinking the female plugs on the input connectors to the lamp driver may be bad. I don't have any replacements on hand so I'll have to order some - any other ideas?"

Thanks for the tip, but I tried putting the DMM on voltage setting between the connector pins and ground, and for the faulty lights I'm not getting anything.
I also tried jumpering the hot lug of a working light to the hot lug of the ones that don't work and they do light up, so it seems like they're correctly grounded.

I looked at the schematics and it looks like the faulty lights are on legs 3,6 and 7 of the U1-U4 chips.
Maybe J4-15 which drives bit 0010 is the one that's acting up. I'll check if leg 2 lights are working tomorrow, that could validate the theory.

In any case I guess I'll need to redo the connectors just to be sure. Am I correct in thinking the under the playfield wiring is ok given the tests I've done?

I wrote the last post before I went to bed, I slept on it, and this morning I understand what you mean...
So the bare wire on the PF isn't a ground as I thought, but a 5V coming from the rectifier board, correct? So that means I wouldn't be seeing any 5V on the lamp driver in any case.
So my DMM test isn't saying anything, but I guess my jumpering test does (what I was referring as a hot lug was in fact the ground lug then).
I guess that still points to J4 so I'll repin it and get back, unless somebody tells me my logic is flawed...

Thanks!

Alright, so I repinned the board and connectors to no avail.
I was wondering if maybe my "known good" board had gotten damaged by the wiring on my BOPP so I put it back in the Strikes n Spares where it came from and it's all good. Also, I put the DMM between the 5.4VDC and the lamp driver pins and I'm getting nothing on the pins linked to the faulty lights, so definitely the driver isn't acting properly.
So now I have to think that something's off with the connectors from the MPU (which I had redone before the resto, but maybe I screwed up something then) and the lamp driver.
The MPU is a brand new Alltek so I'd have to strike that one off the list as well.

Yes I do understand that test was no good. That's why I retested with the DMM between the 5.4V (instead of the ground) and the LDB. I then see voltage on the good lights, nothing on the bad ones.

Thanks.

I also jumpered the bad lights from a good pin with gator clips and they do light up so I'm positive they're not getting grounded by the LDB.
I was thinking of trying to either "manually" feed 4 bit addresses to the board through the J4 pins - is that feasible? If so what voltage would that be? 5.4V as well?
If not, how would I troubleshoot each of these?

For right now I'll test continuity from the MPU to the LDB both ways, which I guess would troubleshoot your first 3 hypothesis.
For the 4th one I'm not sure how to test.

I was coming for a quick update on my latest test and just saw your post... let me post this real quick so I don't lose my thought
So I tested female to female every pin that feeds into J4 (I was looking at the schematics, the same as the bottom diagram in your post above) and all of them have continuity.
I just redid the pins on one of the LDBs and the other one has the same issue, so I'm ruling that out as well.
All I'm seeing now is a short between two wires coming into J4, or something's wrong with the MPU.

Ok I'm putting the kid to bed then I'll come back and read your post.

Here's a thought! The wiring between the MPU and the LDB is the same on all Bally machines of that era, right?
I should be able to swap out the MPU with a Strikes n Spares one and see what happens, right?

But first I'll try unplugging the two connectors you mentioned and see what happens.
Many thanks to all for tht tips so far.

Well son of a gun.
I unplugged those two connectors from the MPU and those dang lights light up

And here's the issue.
I screwed on the weight tilt backwards on the coin door and it was making contact.
I put a plastic baggie to insulate it and the lights light up!

IMG_0092 (resized).JPG

Man I think it would have been weeks until I'd figured that one out.

Bravo CactusJack, you made my day.
And thanks to all others who chimed in as well.

pasted_image (resized).png

(The ones that aren't lit don't have bulbs...)

CASE CLOSED!