Sometimes a digit or segment can be burned out. It could also be a lead on the glass, solder joint, continuity issue between the joint and the edge contact, dirty edge contact, pitted edge contact, dirty connector pin, broken wire, bad connection on the other end, issue on the display board, or something else.

With the power off, swap the displays. Does the problem follow the display that originally had the problem, or does the problem remain in the same player position?

A cold solder joint on the display connector is a very common cause for this. If you look at the bottom side of the header pins it should be easy to spot. Reflowing all of the pins is quick and easy and will let you know right away if you have a deeper issue. Even if it does not look like a cold solder joint, reflow them anyway just for good measure.

Ok, coffee has fully kicked in. My previous response was more thinking about Bally displays. With the Williams check the pins at the cable connector at the edge of the board as well as the pins running to the glass itself. If the glass has come loose from the PCB, check for broken legs leading to the digits that are out.

The solder joints from where the glass connects to the PCB can break / lead rips. Check there, specially since millions is going to be an outside pin(more commonly broken).

This is for a Gottlieb display, but the same concept applies if there are broken leads on the glass.

http://pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Display_Does_Not_Light

The schematics should show it.

On the GPM pic, digit 7 is the two pins marked A7. They're both the same thing and it looks like only one is wired on that pic.

The broken lead is the problem. I can tell it is for the millions just by how the track runs inside the glass. Id use leaded rosin core solder too. You want something that is going to flow the easiest and be sturdy here, and i don't think that is silver solder.

This is incredibly risky, but you might be able to grind out some extra glass if you need to reach the lead. I would only try that as a last resort.

How is the back of that original PCB tracked. Maybe you can just attach the two A7 pins on the solder side of the PCB to get continuity back.

Yes, if there's no track connection between the two A7 pins on the back solder side of the PCB, then just connect a jumper wire between the two A7 pins.

nope attaching the two a7's won't work since there is no lead going into the glass.

Look like this lead is broken/cut as well, but maybe I'm just seeing things

trace_(resized).jpg

As for the front side, the display is already not working right, so I'd definitely try to carve a little bit of the glass out with a sharp x-acto like Andrew said if you're gonna replace it anyway.

You don't need much to do it if you can probe it and turn it on. And it is low amperage, so you can put a jumper wire in there to do it without fear of it burning up.

If you even need to, I'd take a very sharp x-acto, gently carve out a tiny bit of the glass, just enough to shove like a 24 awg solid core wire in there. Try to do it without carving out glass first.

Tin a wire, stick the wire in there for it to make contact, leave enough of the wire stripped so you have access to heat the exposed wire without heating the end directly that is touching the glass. It should heat up and adhere itself to the exposed lead just from the tinning and you'll be in business. I do this for very fine board work with tiny little traces, and it works fine. After it is tested and working, tape down the wire so it doesn't break off because it'll be really fragile. And if it breaks off, just do it again. That'll prevent a messy soldery mess on the glass and potential damage.

You can also tape the wire down first too with like an inch or so at the end untaped, enough to manipulate it to solder it in place. That makes it easier to solder and will keep it from breaking off in the taping process.

Another option may be to use car defrost repair compound or conductive silver repair glue. e.g. something like this maybe:

www.ebay.com/itm/121747544740

I've never used it so can't vouch for how effective it is, but do a search on ebay for more options.

There's videos on Youtube of guys repairing their car defrosters with compound repair kits. Worth looking at to get an idea.

Just a thought, if you do consider going this route, I'd test it first with two bare wires taped to some glass with their ends close to each other to see if you can bridge them and make an effective connection before using it on your actual display.

Wire glues don't work very well at all in electronics. If they did, everyone would use them instead of soldering. The problem is that they add additional resistance into the circuit path. Draw a line with the stuff and grab your DMM, and you'll see even a 1" line has several ohms of R from all of the millions of microscopic breaks in connectivity in the path.

Wire glue has plenty of practical uses elsewhere though, like defogging. But I wouldn't trust using it on electronics.

Granted, but this a specialized repair where solder isn't sticking, and it's not a 1" break.

This silver conductive pen states low resistance:
www.ebay.com/itm/262005129796

This type of display repair has been done before:
https://pinside.com/pinball/forum/topic/fixing-a-dead-dmd-column-or-row-cherry-4205-dmd#post-322449

This one failed but I think it would have worked better with thin flex wire.
https://pinside.com/pinball/forum/topic/dmd-row-9-is-out

I would say the trick is to use wire between any distance of break, and use thin strand wire so it's less stress on the repaired joint.

Good point

This thread helped me get the tens digit back for my Taxi bonus meter display, thanks from me too!

Had the problem isolated to the display but wasn't sure where to go from there. I'm curious what the grey goop is that runs across all the leads, and why a lead would break beneath it, is it corrosive?

I'm having a similar issue. After boot up. Player 2 and 4 are missing the first digit. Player 1 sometimes only shows 1 digit. If I am the game within 5 minutes minutes all digits are back to normal
I tried to swap a display that showed all digits to one that was missing on and the good display now doesn't show the first digit so don't really think it's the pinscores. Could be a short? Loose connection. Any ideas and possible fixes would be appreciated.