williams system 11b switch matrix issue

a_wookie

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i have a system 11b game that i am having a issue with. i noticed multiple switch problems so i put the machine in switch edges test mode and cleared all the optos/through. At this point there is no closed switch's. if i close any switch in column 3 i get a message " short to ground row 5 wht/blu ". this will be whatever row the closed switch is in.

this seemed that i had a switch column short to ground, but i carefully checked the column and nothing. so at this point i decided i needed to isolate if it was in the head or the cabinet.

My next step was to remove conectors 1J8 1J10 (switch row and column).I then put a diode in a test clip and bridged the matrix manualy to see if my issue was in the mpu.
Sure enough i am still getting the short to ground error on column 3.

schematics showed Q44 drove column 3 but i tested Q44 and its good.

so my question to anyone is, what should i try now? u40?


thanks in advance
 
Have you tried reseating the connectors on the MPU and Interconnect board? I've been having issues with my Whirl Wind and that seemed of fixed the problem knock on wood. Multible switches were being activated by one.
 
Have you tried reseating the connectors on the MPU and Interconnect board? I've been having issues with my Whirl Wind and that seemed of fixed the problem knock on wood. Multible switches were being activated by one.


yes, well sort of. i completely removed the mpu you from the cabinet wiring by removing 1j8 and 1j10. then used a jumper and diode to manually simulated a switch closure. i still had the issue, this ensured 100% To be a " on board issue".


but thats neither here nor there, it is fixed now. it was u40 as i thought. i replaced u39 too.


thanks for the help though, i pretty well knew what the deal was. I even make service calls.
but i just wanted someone to say "yep your on the right track. or ya same thing happened to me"

thanks
 
My buddy test my MPU and he said it wasn't a switch matrix so I was at a lost then. Just few weeks ago I went on a search for some loose wires and I tracked down the switches connectors and pulled em all. Still couldn't find nothing but when I plugged em back up and played the machine and I had no issues. Maybe I have something loose somewhere but I'll leave well enough alone. Here a video of the problems I was having.



http://www.youtube.com/watch?v=mV74ENOs3Ag
 
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