As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 1731 JFK-BDA, AIR RETURN TO JFK DUE TO HF INOP. HF RADIO VERY GARBLED AND UNREADABLE TRANSMIT FUNCTIONS. READABLE ON THE OTHER END (HIGH FREQUENCY (HF) COMMUNICATION SYS). REMOVED AND REPLACED CONTROL I/O MODULE IN MAU NR 1 CARD 6 IAW AMM 31-41-05. PERFORMED OPS TEST OF HF SYSTEM, OPS CHECK GOOD.