What was found
HF TRANSMISSION AND RECEPTION ARE INOP, WEAK, GARBLED INTERMITTENT, ETC. AT ALL CREW STATIONS. (1 = L HF, 2 = R HF). LEFT HF WILL NOT TUNE. REPLACED LT HF COMM TRANSCEIVER FOR TROUBLESHOOTING. REMOVED AND REPLACED LT HF COMM TRANSCEIVER. DID NOT FIX PROBLEM. REPLACED TRANSCEIVER AND SWAPPED CONTROL PANELS, NO HELP. NEEDS COUPLER. REPLACED LEFT HF COUPLER ( M241), OPS CKD GOOD.