When I turn on the machine, I get the attached picture while the MPU boots. When the score displays are all zeros, they work correctly. When the machine tests the displays, the #3 and#4 score displays work correctly and the Player 1 and 2 goes all the same 1,2,3,0,1,2,3,8,9,0,1.... and repeats. There is similar on the error on the credit/ball/match display. I believe it is something on the MPU causing this, but not quite sure where to go next after reading all the system 1 display troubleshooting guides.

It's not a segment issue, it's the number being sent issue. Please don't tell me ni-wumpf because I wouldn't have even bought the thing if I thought it needed a new MPU.

Thanks in advance.for any tips, pointers, links or help.

BTW, everything else on the game seems to be working correctly.

2015-03-28 17.38.32.jpg

I am going to replace Z16 and will report back for anyone that may be having a similar problem.

Z16 was the culprit. I'm not sure if it was a bad solder joint, or a bad chip. I replaced the chip from a junk board and it's working great..

From here: http://tuukan.fliput.net/sys1_en.html#cpu

Display control
The displays are controlled by U6, with a few TTL IC's. 7-segment decoders Z16 and Z17 take care that the numbers shown look correct - if the displayed numbers look strange then one of these is probably gone. Z16 controls player 1 and 2 displays and the credit display, while Z17 handles player 3 and 4 displays. On score display driving there is a small circuit that makes number 1 to be shown with an extra eighth segment in the middle of the digit instead of the usual two right side segments. This is done with gates Z13/Z14/Z15. Suspect those if there are problems in showing number 1. The displays are multiplexed, meaning one digit at a time is shown. Digit selection signals come from gates Z18..Z21.