What was found
PIT - FLT 385 - EN ROUTE FROM PHL-MSY, AT FL250, THE CABIN ALTITUDE BEGAN TO CLIMB MODERATELY. FLIGHT DESCENED TO 10,000 FEET WHERE CABIN WAS REGAINED. FLIGHT THEN DIVERTED TO PIT AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED AND NO OXYGEN MASKS WERE DEPLOYED. MAINTENANCE ACCOMPLISHED FUNCTIONAL TEST OF CABIN PRESSURE CONTROLLER. CONTROLLER FAILED STEP NR 12 OF TEST FOR LOW VOLTAGE. REMOVED AND REPLACED CABIN PRESSURE CONTROLLER. FUNCTIONAL TESTE AND OPERATIONAL TEST GOOD. (M)