RE: TECH: LL - vector distortions (y)

Hi

I once experienced very similar problems with an asteroids board once which
is very similar to the one in my LL. Turned out to be an problem in or
around the AD561 / DAC such that when the 5th order bit went high it somehow
dragged down the other lower order bits. It resulted in similar
regular/repetitive error steps as you describe.

Replacing the AD561s with new ones totally sorted the problem out in one go.
Trouble is the chips are either expensive to buy new, and hard to find as
working seconds, unless you buy a dead board of ebay and pull them out etc.

Check the very useful Asteroids Encyclopaedia for further tips :-

http://www.ionpool.net/arcade/asteroidtech/asteroidsrepair.html#V1

Hope this helps.

Arch.

-----Original Message-----
From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org]On Behalf Of ishagi@netzero.com
Sent: 05 September 2003 13:35
To: vectorlist@vectorlist.org
Subject: VECTOR: TECH: LL - vector distortions (y)

I picked up a nice LL last weekend.
The game worked but had all the Y vectors
squished into horizontal lines. This was
fixed by replacing one of the 7497's. It
also lost cp input and that was fixed by
replacing the LS251.

Now the game plays fine BUT, as the lander
drops vertically, sometimes at specific "altitudes",
the ship will distort and flip around or elongate
in the Y direction. This happens at perhaps four
or five places on the Yaxis. Also the mountains
will show distortion in the vectors at these points.
When trying to land on a 5X, the lander will enter
the landscape and "land" about 1" into it successfully -
so it seems the Y position is offset somehow (though
landing on the lower 2X is correct).

I've looked at the counters and DAC and can't find
anything obvious. Any ideas where else I should look?
The SM? Another part of the VG circuit? Roms?

Thanks, SPW, kanata, on, canada

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Received on Fri Sep 5 10:04:01 2003