What was found
AFTER TAKEOFF AT APPROX 2,500 FT, THE LT ENTRY DOOR (L1) DOOR LIGHT CAME ON. ACCOMPLISHED CHECK LIST. THEN HEARD A LOAD NOISE WITH AIRCRAFT PRESS CLIMBING. RETURNED TO SFO. AFTER LANDING, FOUND DOOR LOCKING LUG BROKEN OFF. ACCOMPLISHED DETAILED INSPECTION OFF L1 DOOR MM. REPLACED UPPER AND LOWER AFT LATCH ROLLER CRANKS. ACCOMPLISHED ADJUSTMENT CHECK AND LEAK CHECK OF L1 DOOR. PERFORMED PRESSURE CHECK OF L1 DOOR. PRESSURE CHECK GOOD.