Williams System 6 trouble

[USSEnterprise]

My Tri-Zone recently started acting up. When it boots, half of the game's displays show random characters, and the other half show nothing. I have yet to replace the inter-board connector, but it has given me no trouble thus far.
Here's a pic of the displays
http://s33.photobucket.com/albums/d75/Starbase89/?action=view&current=DSCF0110.jpg

[grantspain]

thats an interesting fault,not that i have worked on this system before but to me it would certainly point towards bad signal connections or the i/c that controls the display data
i have had similar faults to this on older pins and it was down either or both of the above

[ChadTower]

Odds are high it is the 40 pin interboard connector he mentioned.  Reseat it, if that clears it up, you'll need to replace the connector and header pins. 

[Ken Layton]

That connector is a very big source of trouble. Replace both the male and female portions of it.

[USSEnterprise]

Can the driver and MPU boards be soldered together, either directly or with bits of wire, so this is never again a problem? I know it will probably bring down the value of the machine, but we don't plan on selling this one.

[USSEnterprise]

Alright, I was just reseating various chips and connectors on the boards, and when I reseated a 6820 chip on the driver board, the machine came to (partial) life. It plays and keeps score now, but several of the computer controlled lights, such as the shoot again, bonus, and target lights are either locked on or don't function at all. Is this all related to that chip?

[D_Zoot]

I suppose you could solder the two boards together,  but I wouldn't, it would make it a bugger to service in the future if you had board problems.  The terminals to repin the boards are readily available and it isn't any more work than soldering wires in.

On your lamp problem,  see if you can figure out if all the locked on lamps have a "column" or "row" in common (the manual is your friend here).  From there you would need to trace the path from the driver transistor to a 7406 or 7408 chip to the PIA (which would be a 6821).  A logic probe or scope would be real handy for figuring this out.  If fiddling with chips makes problems come and go I'd be looking for bad chip sockets.

D

[ChadTower]

Hard soldering those connectors would fail very quickly.  That many solder connections, in a brittle interboard connector, in a heavy vibration pinball machine, just wouldn't work very long and would create ghost issues forever forward.