What was found
AFTER T/O, GEAR SELECTED UP, ALL 3 GEAR UNSAFE LIGHTS ILLUMINATED, GEAR DOOR LIGHTS DID NOT ILLUMINATE, GEAR HANDLE STAYED ILLUMINATED. F/A'S REPORTED BOTH MAIN GEAR WERE DOWN. RETURNED TO THE FIELD AND ACCOMPLISHED A UNEVENTFUL LANDING. FERRIED FOR REPAIRS. DUPLICATED PROBLEM ON JACKS. ADJUSTED NOSE WHEEL CTR PROX SENSOR IAW AMM 32-61-06-830-801. ALSO ADJUSTED NOSE WHEEL CTR PROX SENSOR IAW AMMM TASK 32-61-06-830-801, OPS CHECK GOOD. PERFORMED OPS TEST OF THE MLG PRIMARY EXTENSION AND RETRACTION IAW AMM TASK 32-31-00-710-801. OPS CHECK GOOD, ACFT OK TO CONTINUE SERVICE.