Problem with Asteroids Self test.

Been working on another board today. Finally got it almost 100% The final
thing that was holding me up was a dead halt line so I had no Z output. So
now I have video and it works and plays great until you try to switch to
test mode.

It's does a bunch of fast beeps (normal beep you get when all is good just
repeats) and spits up random diagonal lines, and sometimes you can see the
cross hatch.

Sometimes it will stay this way when switching out of test mode.

On occasion it will take a second or two and will display a normal test
screen.

If you power up with the test mode switch on, it comes up in test mode just
fine. Naturally it displays no errors, or ram beeps.

At first I thought it might be a bad ls251 @l10 I had a couple of those go
out causing fire problems. So I tossed one in there. No change

The not Sinp is low, and I figure if the the 3khz wasn't working I wouldn't
be able to fire or do hyperspace. But those work.

Bypassed the L2 coil, C73 cap and R88 (all of which check good), grounded
pin 12 of L10 no change.

So I'm at a loss.

What does the board need to run self test?

I'm using original known good roms, and have even tried replacing them with
new burned ones, and swapping out the CPU.

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Received on Mon Feb 1 23:58:37 2010