Please help with Williams Robotron CPU

DocRotCod

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Donor 2015
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I had a dead CPU board and it was the IC at 7f. Replaced and the board came to life. Someone had one of the MUX chips backwards so I replaced and the games up.

The problem I'm having is when the widget board is connected, it passes the startup tests but right before the game comes up it resets. When the widget board is disconnected, it boots fine and coins up, goes into setup, etc.

I can take another CPU board and everything works fine with the same power (I am using a switcher), widget board, RAM, etc.

Obviously it is one of the chips on the CPU board, just not sure where to look. Any help is greatly appreciated.
 
friend of mine's Sinistar does the same thing. never bothered unplugging the input board. I was reading somewhere that the CPU could cause this. but if you have 2 main boards doing the same thing then... balls.

the tricky part is the game isn't alive long enough to get to test mode. unless maybe you can get there with the input board unplugged (the wiring to the rom board is for the coin door, if you didn't know, so the test panel will still work), progress to the input test, and then plug it back in.

either it will reset again or it will stay. it'll probably throw up a bunch of switch errors and I'm not even 100% sure off hand if they would clear themselves if it's plugged in again.

I don't have one of these here to test this on. so it's up to you. :)
 
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