What was found
DURING FINAL, AUTOPILOT DISENGAGED FOLLOWED BY MASTER CAUTION ELEC SOURCE OFF, NR 1 ENG ILLUMINATED. RAN QRN 6,9 --> STARTED APU GEN SWITCH ON NR 1. CONTINUED NORMAL APPROACH & LANDING. ACFT GROUNDED. INITIAL EVALUATION IDG FAULT ON GCU 28743. SWAPPED NR 1 & 2 GCU, NO HELP. REQUIRED IDG CHANGE DUE TO GCU SWAP REQUIRES BOTH ENGINE RUN TO OPS CHECK GCU. SWAPPED BACK GCU WITH ORIGINAL POSITION. ACCOMPLISHED NR 1 AND NR 2 ENG GCU INSTALL TEST IAW AMM 24-21-81. ALL TESTS PASSED. GROUND RAN BOTH ENGINES AND TRANSFERED POWER BETWEEN APU AND BOTH ENGINES. ALL TESTS PASSED. FOUND NO DEBRIS IN IDG FILTERS IAW AMM 24-11-11. REMOVED AND REPLACED NR 1 ENG IDG, IAW AMM 24-11-11. PERFORMED OP CHECK OF #1 ENG IDG IAW AMM 24-11-00-700-802. OP CHECK PASSED.