What was found
ON GEAR RETRACTION, RIGHT MAIN GEAR A GREEN LIGHT ILLUMINATED AND STAYED ON FOR FLIGHT. GEAR INTRANSIT A AND B SYSTEM GREEN LIGHTS ALL INDICATED NORMAL ON GEAR EXTENSION. GEAR FAILED TO LOWER MANUALLY FREE FALL GEAR PROCEDURE OK. TRIED LOWERING GEAR BY ELECTRICAL OVERRIDE. DOORS OPENED OK, BUT PROCEDURE FAILED TO LOWER THE GEAR. PERFORMED EXTENSIVE GROUND CHECK, GROUND CK DUPLICATED DISCREPANCY AND ISOLATED TO LANDING GEAR CONTROL BOX. INSTALLED SERVICEABLE LANDING GEAR CONTROL BOX. PERFORMED EXTENSIVE GEAR SWINGS, OPS CHECK GOOD. (P/N 12038594501) (S/N 120040R) ON, (S/N 120282) OFF.