What was found
AFTER T/O LT GEAR DOOR AND GEAR UNSAFE LIGHTS WERE FLASHING ON AND OFF FOR ABOUT 20 SEC. THEN ALL LIGHTS WENT OUT. OVERFLEW HLN AND DIVERTED. USED ALTERNATE GEAR EXTENSION FOR LANDING PER FSM. LANDING UNEVENTFUL. FERRIED FOR REPAIRS. INSPECTED MLG ALTERNATE EXTENSION CABLE FOUND TO BE WITHIN LIMITS, DETAILED WORK PERFORMED AND PRIMARY EXTENSION AND RETRACTION LANDING GEAR SYS, OPS CHECK GOOD. REPLACED PSEU AND LT MLG UPLOCK PROX SENSOR. OPS CHECKS GOOD. PERFORMED OPS CHECK FLIGHT WITH NO DISCREPANCIES. RETURNED TO SERVICE.