Atari Gauntlet: garbage colors on player sprites

terrorinstinct

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The other day I noticed my Gauntlet upright was showing some garbage colored pixels around the edges of the player and monster sprites. Ghosts had flickery white outlines, the elf's bow and parts of his face were red, the shading on the wizard was blue when facing left, etc. Pushed on all the socketed chips I could see in case they had worked their way out but no change. The weirdest part is that when I line up multiple characters together (like the warrior and the elf on the same horizontal axis, the weirdness disappears while they are lined up. When I move the warrior out of line the problem reappears one pixel at a time. My gut says sprite RAM but I would like to get an expert opinion before I deploy the parts cannon, especially since I believe the RAMs are soldered and Atari PCB traces are seemingly made of peanut brittle these days.
 
All right, it's been a month and we still haven't been able to get this board functional. Time to get the think tank on this.

What's been done to it so far:
  1. Washed PCB and reseated sockets. This revealed/washed out/summoned weird schmutz on a bunch of the sockets.
    gauntlet socket damage.png
  2. Replaced sockets used by sprite and program ROMs since they all had schmutz on at least one pin. After this and (1) it started watchdogging with a handful of garbage pixels. Service mode was the same deal but with garbage tiles instead.
  3. Replaced sockets used by sound ROMs, since we noticed they were also messy. No effect.
  4. Verified program ROMs with a programmer against a known good set.
  5. Replaced RAM sockets pictured and tested the RAMs (Inmos 1420s I believe) with an 80s vintage chip tester. All tested good, but after reinstalling the RAMs I got the text only from attract mode for one boot only.
    gauntlet redtext.png
We're at the end of our collective ropes here. Can anyone tell me what's going on here, or possibly who to talk to for repairs?
 
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