What was found
DURING CLIMB CREW HEARD A LOW INTERMITTENT NOISE FOLLOWED BY A LIGHT SMOKE ENTERING THE COCKPIT THROUGH THE CEILING VENTS. CREW TURNED OFF PACKS & SMOKE DISSIPATED. CREW DECLARED AN EMER & RETURNED WITHOUT INCIDENT. INSPECTED & PERFORMED ENG RUN AT DIFFERENT POWER SETTINGS DURING NR 1 PACK OPERATIONS. CONFIRMED RUMBLING OF NR 1 PACK & SEIZED ALL OTHER SYSTEMS. OPERATIONS CHECKED NORMAL IAW MM 72-00-00 21-51-00 REF ITEM NR 2 OF NR 1 PACK MEL. R & R LT ACM IAW AMM 21-51-03. OPERATIONS TESTED LT PACK SYS, CHECKED OK IAW AMM 21-20-00.