What was found
WHEN CENTERLINE WAS EXTENDED ON APU, THE RIGHT SOURCE OFF LIGHT ILLUMINATED. FOLLOWED QRH PROCEDURES. UNABLE TO GET APU GENERATOR TO POWER RIGHT SIDE. IAW AMM 24-21-00-501, 700-803 AND 700-802 VERIFIED POWER TRANSFERS SYSTEMS TO BE WORKING, BETWEEN NR 1 IDG AND APU. NR 2 IDG IS INOPERATIVE. VERIFIED OIL LEVELS IN THE NR 1 IDG AND APU. RAN TESTS ON POWER BUS TRANSFER PER AMM 22-11-00, ON BPCU IAW AMM 24-21-21, ON APU GCU IAW AMM 24-21-81 AND DFCS SYSTEM TEST IAW AMM 21-11-00. THE AIRCRAFT WAS GROUNDED.