What was found
LEFT HF RADIO TRANSMISSION PROBLEM. LEFT HF RADIO DOES NOT TRANSMIT LOOKING AT TIMELINE OF FAULTS BOTH 23-11071 AND 23-11082 HAVE OCCURED LAST 3 OF 4 FLIGHT LEGS WITH 23-11071 OCCURING MINUTES BEFORE SECOND FAULT SUGGEST LEFT HF COUPLER MAY BE AT FAULT. REF FIM DMC-B787-A-23-10-F1-16A-421A-A LOCKING. REMOVED AND REPLACED LH HF TRANSCEIVER IAW AMM 23-11-05. OPS CHKD IAW AMM 23-11-00-00A-320A-A. OPS CHKD GOOD. PERFORMED DIRECT COMMS TEST WITH NEW YORK COMMS. SUCCESSFULLY TRANSMITTED & RECEIVED COMMS. NO OTHER DEFECTS NOTED.