What was found
(CAN) CREW REPORTED THAT THEY HAD AN ATC NR 1 AND NR 2 FAILURE. CREW ALSO REPORTED TCAS FAILURE. DUE MEL RESTRICTIONS FOR DUAL ATC FAILURE, ACFT WAS UNABLE TO CONTINUE FLIGHT AND DIVERTED. MAINTENANCE CARRIED-OUT TROUBLESHOOTING, THEY FOUND TCAS COMPUTER AT FAULT, CAUSING ATC 1 AND ATC 2 FAIL LIGHT TO ILLUMINATE. REPLACED TCAS COMPUTER AND CARRIED-OUT TCAS OPS TEST IAW AMM 34-45-00-710-801 WITH NO FAULT FOUND. PERFORMED ATC 1 AND ATC 2 OPS TEST IAW AMM TASK 34-53-00-710-801, FOUND BOTH ATC 1 AND ATC 2 SYS SERVICEABLE. TCAS COMPUTER REPLACED, PN: 066-50000-2221, SN: 3897, TSI 3.