Stargate MPU issue

saltbreez

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Hey Guys,

Here another tough one: A Stargate MPU that is almost to boot. There was a lot of cleanup on this board, but I believe I can rule out the video address generator, the count 240 circuit and the video shirt registers.

Look at the picture; the rug is correct untill just past 1/2 way down the screen, then for about 1/3 of the screen it seems to repeat the pixel above.

Any ideas?

picture.php


Saltbreez
 
Hey Guys,

Here another tough one: A Stargate MPU that is almost to boot. There was a lot of cleanup on this board, but I believe I can rule out the video address generator, the count 240 circuit and the video shirt registers.

Look at the picture; the rug is correct untill just past 1/2 way down the screen, then for about 1/3 of the screen it seems to repeat the pixel above.

Any ideas?

picture.php


Saltbreez

No one at all?!?!?

Saltbreez
 
No one at all?!?!?

Swap your video address decoder at 3C for known working one, then take a look at the 74153 multiplexers at 4e, 3d, 3e, 4f. From just the look of that problem that's leaning me towards bad video address decoder at 3C.

- James
 
Swap your video address decoder at 3C for known working one, then take a look at the 74153 multiplexers at 4e, 3d, 3e, 4f. From just the look of that problem that's leaning me towards bad video address decoder at 3C.

- James


Bingo, Thanks James. 3C decoder it was. You know I give this advice all the time, you would think I would have tried that here....

Saltbreez
 
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