Re: Centipede Board #2 - Sprites - Almost Fixed!! Any techs see this, jump right in.


Fredster wrote:
> It has to be comming from the -212 Rom at H/J 7. Check the continuity
> of the traces around that chip. See if it is grounded (pin 12) okay.
>
> The output of that chip goes to K8 and J8 LS157's. Then it goes to the
> LS166 at J9. It finally goes out to F9 - S74 chip.
>
> Look at all the traces around those chips. See if any of them have
> scratches or bent pins, etc.
>
> It has to be the Rom chips that say 211 or 212. 212 is the "vertical".
> When you said you took them out, does that mean you swapped them or
> just made new ones? You have a good board. Do some swaptronics and
> swap those roms around and see if the problem goes to the other board.
>
> After that, I can't guess.

Hi Fred,
Can't be any of those eproms. I pulled both of them out of the board
and you just get some object moving aorund the screen. Basically, the
sprites are still there. On the good board if you pull out both 211/212
eproms, you get the same picture minus the sprites. I'm going to
concentrate on the buffers tonight. I have to figure out which IC is
responsible for the background. Once I do, I'll follow this to the
buffer that I believe is causing these crazy sprites. I believe I could
Isolate this problem by pulling up the ground on the eproms one at a
time. to see what it effects in terms of the picture.
John

.

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