Edmonton, AB
I have a stern Viper with a display problem. I have tried replacing U9, U10, and U11, the issue persists.
Here is a clip of the issue.
Where do I go next?
(Topic ID: 80545)
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Viper
Stern Electronics, 1981
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So you are missing the millions digit on all displays. The digit enable signal goes from the pia, through a resistor with a cap connected to it, then out the MPU j1 connector to the displays. To troubleshoot, place the game in display test. Put your DMM or logic probe on MPU J1 Pin 7 which i think is the millions digit enable signal. Compare reading to pin J1 p1-6. They should all show similar reading in display t est. If that pin is floating or stuck high/low, check the header pin solder joint and associated PIA socket pin.
I am working off of a Bally MPU schematic. I THINK!!! Stern drives digits the million digit the same way. I am at work and only have Bally schem in front of me....
Well there is a clue.
Stern_1980_Big_Game_Schematics_And_Wiring_Diagrams_Hi_resolution_Page_1.jpg
I would go to the PIA at U11 and check P3 of the PIA with a logic probe / VDC and compare it to the other digit enable pins right next to it. Next check the solder pad under P3 of the PIA, that will tell you if the socket it bad / the output is floating.
I'm reading .75v at pin 3 vs .33 at pin 4, 5, 6 and such. But I've swapped out this U 11 chip already, so it must originate before that even. Also with the bookkeeping functions giving strange results, I'm wondering if it could be something else.
Quoted from Tridentphoto:I'm reading .75v at pin 3 vs .33 at pin 4, 5, 6 and such. But I've swapped out this U 11 chip already, so it must originate before that even. Also with the bookkeeping functions giving strange results, I'm wondering if it could be something else.
Replace the 5101 RAMs then if you book keeping audits are funky and don't save despite being battery backedup. If an audit always goes to some erroneous number, the 5101 is bad or too slow. use PCD5101 in a matching pair get from Great Plains electronics or Arcade Chips. It is rare, but for sure 5101 ram problems can manifest in display issues. Usually it shifts digits to the left or right when i see it.
So, I swapped the MPU in my EBD into the viper, I had the same issue with the displays and millions digit. Then I put the display from my EBD in the viper, and still the same issue. So I put the viper display in my EBD, and the million digit works fine. So it's not the display, and not the MPU. But there isn't a master display board, so does it run through the other board somehow?
Jeff
So, turns out that the displays each needed a jumper on them between pin 11-12 to make them activate the millions digit. And while not yet confirmed, I believe the bizarre digits displayed in the bookkeeping is a result of not having a memory battery. I'm getting a super capacitor next week instead, so then I'll know for sure. Chris solved this in the other thread, so I figured I'd update here too just in case anyone was curious.
Jeff
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