What was found
APPROXIMATELY 10 MIN INTO FLIGHT, NR 1 COMM WOULD RECEIVE BUT NOT TRANSMIT, NR 2 WAS OK. PERFORMED AN AIR RETURN TO PHX. EVERY FREQ CHANGE (6 DIFF FREQ) TRIED. NR 1 COMM CONTINUED TO BE INOP AFTER LANDING, NR 1 COMM NOW WORKED. PERFORMED BITE CHECK OK OF BOTH NR 1, 2 COM, XCURS AND PSEU. AIR/GROUND BITE CHECKED. REMOVED AND REPLACED RECEIVER PER M/M. NR 1 RADIO OPS CHECKS AS PER MM.