What was found
(CAN) ON GROUND, DURING GROOMING THE ACFT, THE AC POWER DROPPED OFF. WHEN IT WAS RE-APPLIED, COCKPIT DISPLAYS SHOWED AC SYSTEM IN MAGENTA (NO COMMUNICATION). FOUND THE EXTERNAL AC/DC CONVERTOR CARD LOCATED IN THE AC POWER CENTER HAD A BURNED TRACE. THE MICROPROCESSOR CARD LOCATED ABOVE THE AC/DC CONVERTER CARD HAD A SMALL AMOUNT OF SOOT BUT NO VISIBLE DAMAGE. THE PRIMARY LOGIC CARD WAS SOOTY AND , WHEN THE SOOT WAS WASHED OFF, A SMALL AREA ABOUT 3 SQUARE INCHES WAS DISCOLORED. AC POWER CENTER REPLACED TO DISPATCH THE ACFT.