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 FAILED SEL CALL CHECK ALSO. GROUNDED - YES. AFTER CONSULT WITH PREVIOUS PILOT, FOUND CB COMM HF 1 OPEN. CLOSED AND CYCLED CB REF B737-900 AMM 20-60-01. OPS NORMAL. PERFORMED HF COMM SYS TRANS B737-900 FIM 23-11 TASK 806 OPS CHK GOOD, HF 1 TRANSMITTED FINE. VERIFICATION FLIGHT SATISFACTORY.