Great, thanks Quench, will do.

* I reflowed all the header pins on the displays, and they're all bright and clear now, no flicker or dimness. Only issue I see is P4 display has the final digit completely out. The rest are perfect. I'll look closer at that later.

* Thinking I'll order a new bridge rectifier for BR1 (maybe others and just rebuild that rectifier board a little while I'm at it). I'll get caps for the SDB as well, and do the suggested mods/upgrades as well where needed.

* Have to figure out why the right sling is dead too... little mysteries, but nothing too crazy I hope.

Thanks for all the help so far, it's been great as always! I'll be back soon with updates as I go. Awesome to see this game that sat for so long coming back.

Quench Update on the Right Slight Shot - checked resistance vs. the left slingshot, they match. Also checked wire continuity from J5 on SDB to the lug on the coil, as well as the wiring to the other side of the coil, all good. Grounding the Transistor metal tab does NOT fire the coil. Normally when that happens I assume a wiring issue, but continuity is there so I'm not certain now.

EDIT - meant to also mention that I checked voltage at the right sling coil and it's 44.4vdc, so the power is getting to the coil just fine. Also, the switches for the sling score points as they should.

EDIT #2 - I used a jumper to quickly jump from the ground braid to the non-banded side lug of the Right Sling Coil and it fired, so I know that works now.

So in Summary:

* Solenoid does not fire when switches are closed, but scoring occurs
* Solenoid fires when non-banded lug jumped to ground
* Solenoid does NOT fire when transistor tab is grounded
* Continuity exists from black-yellow wire on solenoid back to A3J5-14 as expected

Wondering if I should be checking either the transistor, or the path/trace from the transistor to the connection at J5-14?

No continuity from Q11 to J5 pin 14 (or the adjacent pins). Q10 was a little iffy as well, intermittent, but did get contact. The rest of the associated transistors to that chain of connection all show good continuity, so it looks like something between Q11 (maybe a little of Q10 too) needs checking. Maybe it's as simple as reflowing some solder to the headers, I'll pull the board and check some things this morning, then report back on progress.

Update

* Several pins on the J5 header were definitely cracked cold solder and in need of reflow.
* I reflowed all the headers on the board, and added the suggested mods/updates to the SDB via jumpers on the solder side

* Reconnected the SDB and all coils work great now!

** Next up: Order the replacement caps, BR1 bridge rectifier, and a few other odds and ends

Looks like I'm on the home stretch on this one!

Update:

* Reflowed solder to BR1 again, realized I missed the "+" leg of the bridge. Sure enough, that fixed the issue, so my feature (insert) lights are back up and running. I've got about a dozen or so insert lights not working, but given the "loose" feel to the sockets and such, that's not a surprise. I'll tweak, clean and replace/fix the ones that are out.

* Coin lockout is buzzing like crazy, but I think I can just disconnect that and leave it be, if tightening things down doesn't help

* I cleaned and adjusted all the switches that were iffy, and that sorted them all out

So overall, this project is basically running and "finished" from a technical standpoint. I'll work out the last minor bugs, but assuming no other issues, I think we can call this game revived! I'll report back again when I have it in completely good shape.

Thank you to all, especially Quench, for all the responses, effort and assistance. Couldn't have done it without you!