Continuing overdue work on my Stern Magic. I am taking a hard look at the flaky score displays. I have always just lived with them but now it's time to rehab them.

I did some due diligence combing the forum and some stuff on YouTube watching some videos by Joe's Arcade Repair. I am learning a lot about these old plasma displays but none of the tech posts I have seen seem to fit the bill of exactly what I have going on.

Trying to capture a display on a pic sucks but i attached a video and a still frame of the video with all 8s. You can see I have multiple things going wrong on these displays.

To simplify I have player 1 display pulled and I am working on it. You can see from the pic and video that the first and last digit have something going on. I have also attached a picture of the top and bottom of the board. Looks like the solder has been reflowed on the pins. I plan on ReReflowing it to see if that helps. I know transistors and resistors are culprits on these as well.

Starting from here is there anything I should check or be aware of. Thanks for all the help in advance!

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OK here are some videos. I reinstalled the #1 display and unhooked all 4 others. The first video will show it on startup flashing through the numbers. The first and the last digit seem to be the ones having trouble. The second close up video is one I took after the machine had been on 5-10 min and I had played a few games and been through the test cycles. it seems the first digit at least kinda fixes itself after warmup. Not sure if this is a thing or just a fluke but I am curious of where to go from here. Let me know what you think. Also you mentioned testing the high voltage, what pins would I do that on. I do know my way around dmm pretty well I can also text those resistors if I know which #s to test. (I remember seeing in the videos Joe was saying the 1 3 5 7 9s were culprits for burning up, is this true on these?)

Got it. So I might be in the market for a new or used on on this display right?

I think the boards are original for what I know. They aren't in brand new shape but they work well.

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I am proficient with a DMM and Solder. Been working on electronics and pinball a while just have not worked on displays up until now. Are those test points pins on the display board? Or are they on the Main Board?

I see now, I was looking at the Score Display board itself for Player 1. Let me put the display in and test those points.

Damn. Not sure what i did, I had the display plugged up but I just slid it in the metal bracket. I was looking at the display board and pushed the backbox door wide open and the display slid out and touched the bracket and , just have shorted the pins when it did. I heard a surge in the lower box and now i got nothing. I can turn on the machine and it goes through stertup until I hear the relay click then it just sits there with the lights on. wont take a credit or start a game. I am checking fuses now.

Well I am back, the game is still failing to startup. I tested all the fuses and they have continuity. After the initial flicker I get 4 flashes and a relay click on the solenoid driver board. Not sure what or where to check for voltage. I was following a test guide but I couldn't find a layout of the MPU to tell me which chips were which.

I unplugged all but the J4 connector. Here are my voltages.

TP1 5.26 v
TP5 5.26 v
TP2 13.8 v
TP3 22.8 v

Yea I built a bench tester and brought the MPU home I'm thinking it may be U10 or U11. Is there any way to test these? They are socketed so I can pull them pretty easy.

Yes it sure did. Swapped 10 and 11 powered up and LED stays locked on. Swap back and I get the same 5 or whatever flashes.

I'm cool with that. I was just about to ask before I ordered, Is there any more weak spots on that board I might want to order parts to upgrade after I replace these chips and make sure it is functional?

I'm not sure how long ago but ai did read this upgrade guide, it seemed pretty legit. I know at the very least if an electrolytic cap is 40 yrs old it needs to go, whether it's causing problems or not. Also I have learned not to cheap out on new caps.

https://www.maaca.org/viewtopic.php?t=25970

Alright, back to work on this board. On advice I replaced not only the U10 and 11 but also bought a replacement for the 6800 chip in U9 (I can get U8 but it will have to be when I order from another supplier that stocks them.)

Here is my problem. I am working off a bench test as the machine is not here. I replaced all 3 chips and I get a solid red LED. I swapped around the new U10 and 11 and same result. So I took out the new U9 chip and replaced it with the old AMI 6800 and BAM! Full Boot (on the bench anyway - 6 flashes)
When I ordered it said this Motorola chip (6802) was a substitute for 6800 IC but obviously something isn't jiving here. I installed it the same way I am holding it in the picture. Any Thoughts?

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Yeah maybe they need to update this. Oh well next time I order parts from somewhere else I will grab a 6800 and the U9. I'm going to get this guy back in the box hopefully today and see if all is working.

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Back on this after a long break. The machine is back up and operating great. I ended up replacing U8, 9, 10, 11. As well as reworking the ground area of the MPU and redoing my battery pack. Since I had to order again I ordered all the caps to rework the Solenoid Driver and put in all the ground jumpers to bulletproof that board.

All that running well now back to my original issue the flaky displays. When I originally posted this topic before I blew out the ICs we were looking at the voltage on those displays. Right now it's reading about 190-191v.