What was found
OFF THE GATE TAXI OUT, FIRST OFFICER`S INSTRUMENTS & EHSI, EADI, CTR HYD ELECTRICAL PUMP 2, OVER SPEED & AFT GALLEY POWERS FLICKERS SEVERAL TIMES ABOUT 5 MINUTES, THEN NORMAL. FOUND RT IDG FREQ LOW AT 386 CPS & ABLE TO DUPLICATE ELECTRICAL POWER FLUCTUATIONS. DISCONNECTED IDG & ELECTRICAL, SYS CHECKED GOOD. R & R RT IDG.