As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ON THE GROUND WITH APU ON, SMELLED STRONG SMOKE FROM AFT GALLEY AREA (NO VISUAL SMOKE). SMELLED LIKE BURNING PLASTIC. SMELL ISOLATED TO GALLEY LIGHT WHICH HAD APPARENTLY BURNED OUT. REMOVED AND REPLACED BALLAST WITH SERVICEABLE UNIT. OPS CHECK GOOD. WHILE ON GROUND WITH APU RUNNING, BURNED WIRE SMELL AND WHITE SMOKE SEEN COMING FROM GALLEY AREA. REPLACED AFT GALLEY LIGHT REACTOR.