Defender troubleshooting continued

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Thanks a ton for the prior information on my Defender! It's getting healther,
but it's not quite up and running.

I've got Defender to the point where it says "Initial tests OK", then the game
resets and goes into the rug pattern again (endless). So far I've had a bad
7432, a bad 7442, and a bad EPROM - all on the ROM board. I do know the main
board is good because it runs in another Defender I have, so the problem is
definitely on the ROM board. It's getting healthier. I know all of the EPROMs
are good now. Any idea what this symptom might indicate?

It semi-sounds like it's having trouble with one of the paged EPROMs, but I
can't be sure, and I'm hoping one of you might have seen the problem before.
Plus, it looks like the ROM board layout diagram has at least two errors on it.
It had the 7432s mislabeled in a copule of places.

Any help would be greatly appreciated!

-->Neil

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Neil Bradley wrote:
> Thanks a ton for the prior information on my Defender! It's getting
> healther, but it's not quite up and running.
>
> I've got Defender to the point where it says "Initial tests OK", then
> the game resets and goes into the rug pattern again (endless). So far
> I've had a bad 7432, a bad 7442, and a bad EPROM - all on the ROM board.
> I do know the main board is good because it runs in another Defender I
> have, so the problem is definitely on the ROM board. It's getting
> healthier. I know all of the EPROMs are good now. Any idea what this
> symptom might indicate?
>
> It semi-sounds like it's having trouble with one of the paged EPROMs,
> but I can't be sure, and I'm hoping one of you might have seen the
> problem before. Plus, it looks like the ROM board layout diagram has at
> least two errors on it. It had the 7432s mislabeled in a copule of places.

Found it! Bad PIA on the ROM board! It wasn't allowing any paging/swapping to
occur. Good indication is that the LEDs didn't go out immediately after powerup.

-->Neil