What was found
(CAN) A/C DEPARTED, AFTER TAKEOFF, CREW EXPERIENCED A COMMUNICATIONS FAILURE. CREW SQUAKED 7600 & RETURNED FOR LANDING. MAINT TROUBLESHOT COMMUNICATIONS SYS. NR 1 COMM FAILED, REPLACED COMM WITH SERVICEABLE VHF UNIT, COMM NR 1 OPERATING NORMAL. AWAITING STRIP REPORT. NR 2 VHF COMM - WIRE CHAFED (NR 2 COMM 'MIC KEY' WIRE) BETWEEN NR 2 VHF COMM & NR 1 AUDIO SELECTOR. CHAFED WIRE GOING TO GROUND. REPAIRED WIRE & CHECKED NR 2 COMM SYS. OPERATING NORMAL. HF - FOUND LOOSE HF PIN IN NR 1 AUDIO SELECTOR, ADJUSTED PIN LOCKING MECHANISM AND RE-INSTALLED. HF STILL HAD TUNING PROBLEM. INSTALLED SERVICEABLE HF REC/EXC AND HF AMP. GROUND TUNING ACCOMPLISHED. D) GROUND CHECKS OF RADIOS CARRIED OUT.