Glitched graphics. Screen changes as board is flexed. Moved around board pressing chips until pressing the custom surface mount chip at B6 changed the effect. Noticed that the corner most pins had come up from the board. After an unsuccessful effort to resolder them, I used some enameled 38 swg wire to solder from the affected pins across to a convenient point on the tracks. Having completed this the graphics are back to normal. The wire is very delicate, and located where someone was likely to grab the board to disconnect the jamma connector, so the work was then covered in some hot melt glue to protect it.
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