What was found
AT 28,000 FL CRUISE JUST PRIOR TO TOP OF DESCENT THE AIRCRAFT LOST ELECTRICAL POWER WITH ALL GAUGES AND INSTRUMENTS FLAGGED, POWER RETURNED AFTER 3 SECONDS AND AIRCRAFT LANDED UNEVENTFULLY IN PHX. MX COULD NOT DUPLICATE THE PROBLEM, TROUBLESHOT FOR OPEN PHASE CONDITION REF AMM 24-21-00, AND SL-24-118. REMOVED AND REPLACED NR 1 GENERATOR CONTROL UNIT, REMOVED AND REPLACED R4 BUS TRANSFER RELAY NR 2 AND R3 TRANSFER RELAY NR 1 IAW WDM 24-24-01. ENGINE RUN OPERATIONAL TEST WAS GOOD. VENDOR BENCH TEST CONFIRMED FAILURE OF GENERATOR CONTROL UNIT S/N RH1075 WITH TEST FAILURE OF THE BR DROPOUT CIRCUITS, K901 RELAY ARMATURE WAS REPLACED TO REPAIR THE UNIT. UNIT ALSO WAS UPGRADED WITH KIT MODS.