What was found
PIT - FLT 158 - AFTER TAKEOFF, AIRCRAFT WOULD NOT PRESSURIZE. RIGHT PACK SHOWED ZERO PSI. MANUAL AND AUTO SYSTEM DID NOT OPERATE. FLIGHT RETURNED TO FIELD AT PIT AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE FOUND THE RIGHT ENGINE BLEED VALVE CIRCUIT BREAKER POPPED AND THE RIGHT ENGINE HIGH STAGE PNEUMATIC SYSTEM REGULATOR AT FAULT. REMOVED AND REPLACED REGULATOR AND RESET CIRCUIT BREAKER. RUNUP, PRESSURIZATION AND BLEED CHECK NORMAL. RIGHT PACK 20 PSI AT IDLE AND LEFT PACK 20 PSI AT IDLE. (M)