What was found
IN ARM POSITION NO EMER LIGHTS WORK AT ALL. IN ON POSITION ALL LIGHTS WORK EXCEPT THE UNDER SEAT LIGHT AT SEAT 10 AND THE LOWER MAIN CABIN DOOR LIGHTS BOTH FORE AND AFT. SUSPECTED NUMBER 1 PACK FAILURE. PERFORMED THE CHARGING PROCEDURE ONCE YESTERDAY WITH SUCCESS. PERFORMED IT TWICE TODAY WITH NO SUCCESS. CONFIRMED EMERGENCY BATTERY #1 SUPPLY IS ONLY SHOWING 1.0 DC VOLT. WILL NOT POWER MAIN DOOR EMERGENCY LIGHTING. REMOVED AND REPLACED #1 EMERGENCY POWER SUPPLY P/N CBS28·1 S/N 007096 WITH REPAIRED P/N CBS28·1 S/N 3970M. PERFORMED OPS TEST PASSED. IAW AMM 33-50-06 AND 33-50-00.