More Missile Command Woes

JoeB1355

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This board is a total pita -- I had posted when I had stretched video problem, that was bad madsel 74ls163 -- replaced the board was good for a few days

then its crapped out again just flickered static -- bad wdog disbale replaced 74ls42 chip

So now it runs but no left track ball action it just goes right whether you spin left or right. It ends up being a bad 74ls74 chip

All good for 3 more days....

Now its bad again. Looks to me like there are 4 quadrants and at least 4 columns in each quadrant and my data just keeps getting rendered in the first column of each quadrant. All data appears to exist just gets jammed in the same spot... Not any good theory of operation in the MC manual that I found...

I've been tracking signals around but can really find anything missing. Anyone have any clues?

I haven't found any stuck data lines or address lines. Its like a clock that should cycle the columns in a quadrant doesn't count. Yet looking through the schematic it doesn't seem obvious to me and anything I think might be it seems to have activity with the logic probe.

I posted a video here:

http://youtu.be/kvpK3ESMnzY
 
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You got a Pita MC. I wonder If the board you got experienced a Power surge. This would cause your board to develop more problems down the line even after a repair.

I saw your video and honestly can not point you in the right direction. Have you double check your eproms. Something is not decoding right. Either bad ram/Bad eproms/ bad decoding or even bad adressing.
 
You got a Pita MC. I wonder If the board you got experienced a Power surge. This would cause your board to develop more problems down the line even after a repair.

I saw your video and honestly can not point you in the right direction. Have you double check your eproms. Something is not decoding right. Either bad ram/Bad eproms/ bad decoding or even bad adressing.

I have a braze kit on it. I took it off though same picture. I guess I can just swap m6/7 n6/7 and see. They all activity though.

anyone have a good description of how the data gets put on the screen. If my theroy of 4 quadrants and 4 columns in each correct?
 
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