As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT HF RADIO FAILED TO TUNE OR TRANSMIT IN FLIGHT. GROUND TESTED LEFT HF RADIO, OP CHECKED OK. RANG-OUT COAX CABLE FROM M241 AT COUPLER TO LEFT HF TRANSCEIVER M152 READ 1.23 OHMS. JUMPED BETWEEN CENTER CONDUCTOR AND SHIELD. REPLACED LEFT HF COUPLER PER AMM, OP CHECKED GOOD.