What was found
ON PREFLIGHT; EMER LIGHTS FAILED PREFIGHT TEST. COMPLETED TWO CHARGE CYCLES EACH OF 30 MINUTES. EMER LIGHTS STILL FAIL PREFLIGHT TEST. WAITED FOR THE APART TO ARRIVE AND RECEIVED REPAIRED EMERGENCY BATTERY CHARGER P/N: CBS28-1 S/N: 1233M FROM THE CUSTOMER. GAINED ACCESS, REMOVED #1 EMERGENCY BATTERY CHARGER PIN: CBS28-1 S/N: 4188M DUE TO INTERNAL FAILURE, AND INSTALLED REPAIRED EMERGENCY BATTERY CHARGER P/N: CBS28-1 S/N: 1233M IAW AMM 33-50-06. ALLOWED THE BATTERY TO CHARGE AND PERFORMED EMERGENCY LIGHTING OPERATIONAL CHECK IAW AMM 33-50-00, THE EMERGENCY LIGHTING OPERATIONAL CHECK WAS FOUND SATISFACTORY.