What was found
AIRCRAFT EN ROUTE ENCOUNTERED TWO LARGE VIBRATIONS THROUGHT OUT THE ENTIRE AIRCRAFT, PRESSURE FLOW LIGHT WENT ON WITH CABIN CLIMBING AT 1500 FT PER MINUTE. ANTI-ICE WAS IN THE ON POSITION. APPEARED TO BE COMPRESSOR STALL ON ENGINE NR 1. DECLARED EMERGENCY AND LANDED WITHOUT FURTHER INCIDENT. AIRCRAFT WAS NOT OVERWEIGHT. REPLACED THE PRBS VALVES AND ACCOMPLISHED BLEED LUBE. LEAK AND SYSTEM GROUND CHECKED NORMAL. (M)