What was found
SAW RT WING INSPECTION LIGHT GO OFF. IT SHOULD BE ON WITH THE EMERGENCY LIGHTS ARMED & PAX SAFETY SWITCH ON. ON INVESTIGATION, MAIN CABIN ENTRY DOOR EMERGENCY LIGHT WAS OFF ALONG WITH LAV BULKHEAD EMERGENCY LIGHT, WITH THE APU RUNNING, EMERGENCY LIGHTS ARMED & PAX SAFETY SWITCH ON. SHUT DOWN ACFT, BATTERIES OFF. WITH THE EMERGENCY LIGHT SWITCH ON, EXTERIOR LIGHTS WORKED NORMAL AND LAV BULKHEAD EMERGENCY LIGHT WAS ON. ONLY LIGHT OUT WAS CABIN ENTRY EMERGENCY LIGHT. STARTED APU & AGAIN FAILED. REMOVED FUSE AND REPLACED WITH A NEW FUSE. PERFORMED A SATISFACTORY OPS CHECK. WORK PERFORMED IAW AMM 33-50-10