As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO TRANSMIT OR RECEIVE ON HF 1, THE RADIO WORKED FOR 3 TRANSMISSIONS NORMALLY. AFTER THAT, WHEN THE SECONDARY FREQUENCY WAS SELECTED THE "TUNING TONE" ON THE RADIO SOUNDED FOR LONGER THAN USUAL, APPROXIMATELY 5 SECONDS. HF 1 NEVER WORKED AGAIN. HF 2 OPERATED NORMALLY. ACFT GROUNDED. REMOVED AND REPLACED THE NR 1 HF COUPLER, IAW AMM 23-11-61-400-801. ACCOMPLISHED HF 1 OPS TEST STEP I. INSTALLATION TEST, IAW AMM 23-11-61-400-801. SYSTEM CHECKED NORMAL.