What was found
FLT 351 - HNL-JON - DURING THE VERIFICATION PHASE OF FLIGHT AND CHECKING THE HF RADIO SYSTEM, THE NR 1 HF HAD NO TUNE AND THE TRANSMIT WAS INOPERATIVE. RETURNED TO HNL FOR AN OVERWEIGHT LANDING, VERY LOW SINK RATE. REPLACED NR 1 HF TRANSCEIVER (P/N 6223371001). OPS CHECK ON GROUND WITH SFO AND SELCAL CHECK OK. VERIFICATION FLIGHT REQUIRED. PERFORMED OVERWEIGHT LANDING INSPECTION IAW FORM M-121. NO DEFECTS NOTED IN PHASE 1 STEP 2A. OK FOR SERVICE. SUBSEQUENTLY, THE HF COUPLER WAS REPLACED (P/N 792-6140-001) AND VERIFIED AS THE CAUSE. AIRCRAFT RETURNED TO SERVICE. (M)