Against my better judgement, I offered to help repair a Bally Truck Stop for a friend. It powered up and displays looked good at his storage unit but it had a missing transistor at Q18.
Drove it 5 min across town, set it up, pulled the MPU and replaced the missing transistor. The game now plays well, however, my displays are now blank with "8" in each of the four sections.
I can faintly see the correct info displayed at random times. But these number "8"s over power everything.
Also if i disconnect the display connector at J2, the 8s are still present.
Voltages on the power supply all test within spec.
Any ideas what happened?? Thanks

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Nothing seems out of the ordinary on the back. I'm confused as to why they worked and now they dont. But again this stuff is 30 yrs old now.

Could this be the 4514 decoder chips malfunctioning on the display board?

I've tried just the left and just the right. No matter which is hooked up, they each display those 8s in the same spots without the other.

Ive poked around a bit looking for shorted transistors. Didnt see any discretely bad ones. I decided to reflow the header pins while they are out. Now I have this.
Dim, but legible text. Just 2 locked on "0"s now.
3rd spot, 2nd player. 6th spot 4th player.

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Ok...so just was pulling on the transistors to make sure they weren't broken....now a perfect left display??? Lol

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Repeated tbe process again on 2nd display. Pulled on all the transistors. Fixed! They must have had legs smashed together.
Ok..easy inexpensive fix.

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I've had a couple 6803 games in the past and they're just a pain to trouble shoot. The 2 phase grounding, the old flipper mechs, the 555 sockets, etc. This TS does have the mushrooms and it's the first screen printed TS cab I've seen. Most have those crappy decals.

But I'll do my best to get it looking and playing well and move on to the next refurb. Thank you kindly for the guidance and I hope this thread helps someone else with wonky displays.