What was found
AIRCRAFT WAS GROUNDED: PACKS BEGAN TO PULSE WHAT SEEMED LIKE BETWEEN HIGH FLOW AND LOW FLOW, VERY LOUDLY. PULSING CONTINUED AT VARIOUS THRUST SETTINGS. A QUICK PASSING BURNING ELECTRIC SMELL WAS PRESENT, ODOR CLEARED WITHIN 30 SECONDS. MAINTENANCE MESSAGE 36-11040 PRESENT. ACCOMPLISHED FIM 36-11-00-810-812 ENGINE NUMBER 1 PRSOV TORQUE MOTOR SIGNAL IS OUT OF RANGE. REMOVED AND REPLACED ENGINE NUMBER 1 (PRSOV)-PRESSURE REGULATING AND SHUTOFF VALVE. PER AMM 36-11-04 AND RAN TEST. TEST PASSED. ELECTRICAL SMELL NOT PRESENT WITH PACKS RUNNING DURING BOTH APU AND ENGINE BLEED.