As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO TRANSMIT ON HF 1 WHEN TUNING SIDETONE LAST FOR ABOUT 5 SECONDS RECEIVING WORKS AND SELCAL FUNCTIONS NORMALLY. GROUNDED - YES. PERFORMED OPS TEST OF HF COMM SYS IAW B737-800 AMM 23-11-00-710-801 OPS CHECK AND GROUND VERIFICATION SUCCESSFUL.