What was found
BOTH LT & RT SIDE, FWD & AFT OVERWING LIGHTS INOP ALONG WITH AFT OVERWING EXIT MARKING SIGNS INOPERATIVE. RELAMPED BOTH CABIN EXIT MARKING SIGNS & HAVE PLUGGED IN PWR SUPPLIES FOR EACH SIDE, NO HELP. SWAPPED DEU B 300RH4 WITH FWD DEU B, NO HELP. RE-INSTALLED ORIGINAL, EMERGENCY LIGHT SYS TEST OK & EPSU TEST OK, BUT EMERGENCY LIGHTS AT ABOVE LOCATIONS DO NOT WORK. REPLACED EPSU AND BATTERY LOCATIONS 11WL & 12WL. OP CHECKS GOOD.