As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN FLIGHT UNABLE TO XMIT ON EITHER HF. RETUNED NUMEROUS TIMES, MADE CONTACT W/SFO AIRINC AND 2 GOOD SELCALS. DURING FLIGHT HOURS IN, RETRIED HF 2 & HF1 RECEIVE BUT ONLY HF 2 XMITTED INTERMITTENTLY. GROUNDED - YES. CYCLED POWER TO BOTH HF'S #1 HF OPS RESTORED, TEST OK NO FAULTS REFERENCE B737-800 FIM 23-10 TASKS 801 AND 806. NUMBER 2 HF FAILED OPS CHECK. REMOVED AND REPLACED #2 HF RT AND CHECKS OK REFERENCE B737-800 AMM 23-11-21.