1980 Bally display skipping numbers

[kehoe]

Hi there,

I'm fixing up a Space Invaders game. During the pinball diagnostic where the numbers 0-9 should cycle through the display we get numbers 4, 5, 6, 7, which repeats.

Previously we had all displays cycle 0, 1, 2, 3, 0, 1, 2, 3, 8, 9 . We removed the displays and fixed any cracked or missing solder. We also cleaned all the contacts to the boards and displays. It then switched to only showing 4, 5, 6, 7.

Any thoughts on what would be causing this?

Thanks,

Kehoe

[highwayman]

if it's all the displays, try with one unplugged, try doing this for each and see if unplugging one fixes the others.
if not then it's the board driving them.
i dont know what system that game uses, but i wouldnt be surprised if it's a bad 6820 or 6821 pia chip.

[Anthias]

this service guide has a section on display problems that might help: (its a good guide - I have a hardcopy that lives inside my harlem table) http://www.pinrepair.com/bally/index1.htm