As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF WHILE USING HF1-WE FOUND XMIT FUNCTION ON THAT RADIO DID NOT WORK, WHILE STILL ABLE TO XMIT ON HF2. DF NOTE-BEEP HEARD DURING FREQ CHANGE ON HF1 STILL OCCURRED WHILE PRESSING XMIT ALL BUTTONS, BUT BEEP LASTED AT LEAST 8-10 SECONDS, MUCH LONGER THAN USUAL. GROUNDED-YES. REMOVED AND REPLACED HF NR 1 COUPLER, PER B737-800 AMM 23-11-61. OPERATIONS CHECK NORMAL. ETOPS GROUND VERIFICATION SUCCESSFUL.