What was found
FLIGHT 8659 ANC TO ADQ, AIR TURN BACK, EMERGENCY DECLARED. DISCREPANCY, APPROXIMATELY 20 MINUTES INTO THE FLIGHT, THE CREW NOTICED A STRONG BURNING ODOR. THERE WAS NO SMOKE PRESENT. THE CREW DECLARED AN EMERGENCY & RETURNED BACK TO ANC, ARRIVING BACK AT THE RAMP WITHOUT FURTHER ISSUES. AFTER EXTENSIVE TROUBLESHOOTING, MX DISCOVERED THAT THE NR 1 RECIRCULATION FAN WAS FAULTING, HAD CEASED & SMELLED BURNT. FAN WAS REPLACED, OPERATIONS CHECKED GOOD & ACFT WAS RETURNED TO SERVICE.