What was found
AFTER DEPART, LOW VOLT IND & SELECTED AUX VOLTAGE REG WITH NO IMPROVEMENT. SEVERAL SELECTIONS WERE MADE BETWEEN MAIN & AUX REG WITH NO IMPROVEMENT. A/C RETURNED TO AIRPORT FOR A LANDING. INVEST REVEALED A SHORT-CIRCUITED BRUSHBLOCK IN RT ALTERNATOR R, WHICH DESTROYED BOTH MAIN & AUX REGULATORS, WHICH PREVENTED FUNCTIONAL LT ALTERNATOR FROM FUNCTIONING. SHORTED BRUSHBLOCK IN THE RT ALTERNATOR REPLACED WITH A FUNCTIONAL BRUSHBLOCK & BOTH REG`S REPLACED WITH NEW UNITS. ENG`S WERE GROUND RUN & VOLT REGULATORS CHECKED AT 28.5 VOLTS, A/C RETURNED TO SERV.