What was found
VTK ILLUMINATED, BOTH FMC DISPLAYS BLANKED FRQUENTLY DURING FLIGHT. ACFT GROUNDED. BITE CHECK OF FMC'S SHOWS PROGRAM FAULT. REF FIM 34-61, TASK 807, APPEARS TO HAVE BEEN INTERMITTENT. REPLACED LT FMC COMPUTER IAW AMM 34-61-02-000-801 AND 34-61-02-400-801. CROSS LOADED ALL SOFTWARE IAW AMM 34-61-00-470-806. PERFORMED SOFTWARE CONFIGURATION CHECK IAW AMM 34-61-00-750-801. SET DRAG FACTOR IAW AMM 34-61-00-800-801. PERFORMED FMC, OPS TEST IAW AMM 34-61-00-710-801, OPS TEST PASSED.