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 09:05:01 2003