As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, WHILE CONDUCTING HF RADIO CHECK, UNABLE TO TRANSMIT ON EITHER HF RADIO. AUDIO COMES IN NORMALLY. BUT HF TRANSMITTER DOESNT SEEM TO ACTIVATE. GROUNDED - YES. REMOVED AND REPLACED #1 HF ANTENNA COUPLER. REMOVED AND REPLACED #2 HF COUPLER PER B737-800 AMM 23-11-61-000-801 AND 23-11-61-400-801. BOTH HF RADIOS OP CHECK GOOD. HF RADIOS ARE NOW OPERATIVE.