(Topic ID: 105338)

Sys 11C MPU issue

By Andy_B

9 years ago



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  • 4 posts
  • 2 Pinsiders participating
  • Latest reply 9 years ago by wayout440
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#1 9 years ago

I have a Rollergames that is next in the queue to be raised form the dead. Had a fair amount of corrosion on the MPU board that required me to replace the entire reset section and I would say the effects of the leaky batteries are visible over half the board but no worse that turning the solder pads a dull grey.

After finally getting Leon's test ROM to work (had to replace U38) I get all the PIA outputs pulsing as expected but with game ROMS installed I can't get a blanking signal when booting on the bench. I just get the 5v LED lit. My first question is will the board light the blanking LED when booting on the bench and not connected to the pin? This is my first Sys 11 MPU problem.

Despite the lack of blanking LED, when I power on the board the reset pin goes low momentarily then high so I believe that is OK. I get clock activity, IRQ, VMA and all the address and data lines on the 6802 are pulsing.

Before I start shotgunning the blanking circuit components does anyone have any suggestions?

Thanks

Andy

#3 9 years ago

I am aware of this but can't understand what the problem is likely to be if Leon's test runs ok and the game ROMS and sockets are new and buzz out ok.

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