What was found
AFTER MX REPLACED HF1 IN KOA, OPS CHECK NORMAL BY HEARING TRANSMISSIONS ON HF2. PRIOR TO REACHING GATEWAY FIX, ATTEMPTED NUMEROUS CONTRACT ATTEMPTS W/ AIRINC. COULD HEAR OTHER A/C ON HF1. COULD HEAR OUR TRANSMISSIONS USING HF2. USED HF2 TO ESTABLISH CONTACT W/ AIRINC. THEY CONFIRMED NO TRANSMISSIONS FROM US USING HF1 COULD BE HEARD. WE DID RECEIVE A GEED SELCAL CHECK ON HF1. APPEARS RECEIVING FUNCTIONS WORK BUT NO TRANSMISSION FUNCTIONS BEYOND THE A/C NO WE COULD HEAR US ON HF2. GROUNDED - YES. REMOVED AND REPLACED #1 HF COUPLER REF B737-800 AMM 23-11-61/401. OPERATIONAL CHECK SATISFACTORY. ETOPS GROUND VERIFICATION SUCCESSFUL.