Omega Race problem.

Hello folks,

After years of working great, my Omega Race is showing a peculiar problem drawing the player's ship (everything else is drawn correctly.)  Throughout most of the frames of the ship's rotation, everything's fine - but 4 or 5 of the frames where the ship is pointing down and to the left are being drawn with scrambled coordinates.  If you rotate the ship past these frames, it, and everything else, appear normal.  This problem appears in both play and attract mode.
I pulled and verified all EPROMs, and even replaced the factory sockets for the video EPROMs with machine sockets.  The problem doesn't appear to be coming from there.
Since the random garbage coordinates appear to change from game to game, even level to level as you play, I'm theorizing that this could be a RAM chip somewhere in the digital vector generator going bad (in fact, during one game I played yesterday, the ship's shape was actually being drawn as the enemy's shape, for one of the frames of rotation.)
Can anybody shed some light on this or tell me what chip(s) to look at next?  I'll attempt to take a short movie of the problem if my description is too confusing.
Cheers,
-Lewis

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Received on Wed Dec 19 10:06:17 2012