What was found
CTR LANDING GEAR FAIL TO DEPLOY USING ALTERNATE EXTENSION CABLE. BOTH NORMAL AND CONFIG LANDIG GEAR IN DICATION SHOW CTR LANDING GEAR RED. JACKED AND DOWNJACKED ACFT, DISCONNECTED AND RECONNECTED FWD CENTERLINE GEAR DOORS FROM STRUT, FOUND MAIN GEAR INTERLOCK CYLINDER NOT OPERATING, BLED CYLINDER AND OPS CHECKED ALT. GEAR EXTENSION AND MAIN INTERLOCK CYLINDER GOOD IAW MM, 07-11-00-2, 32-31-05-2, 32-32-03-2, 32-39-01-2. ACCOMPLISHED, OP'S CHECK GOOD IAW AMM 32-30-00-5.