What was found
AT ABOUT 13000 FT, ON DESCENT, THE NR 2 TRANSFER BUSS ILLUMINATED, RAN CHECKLIST AND STAYED ILLUMINATED. ACFT GROUNDED. ACFT HAS HISTORY IAW LP 11863942, & 11863925 IAW FIM 24-21, 822 & AMM 24-21-00-700-803. OPS TEST FOR AC GENERATION & CONT SYS, TRANSFERRED PWR FROM ALL SOURCES WITH NO DEFICIENCIES NOTED. DUE TO HISTORY, REPLACED THE NR 2 ENGINE GCU IAW AMM 24-21-81-400-801 BPCU REF AMM 24-41-21-400-801 & GENERATOR CONT BREAKER #2 (C802) & BUS TIE BREAKER NR 2 (C805). ALT DEACTIVATION PROCEDURES USED FOR ALL COMPONENTS CHANGED IAW TABLE 3 ITEM #1. ALL DEACTIVATION PROCEDURES REVERSED AFTER. ALL OPS CK'S OK REF AMM 24-21-00-700-803. PERFORMED TEST 4 TIMES. IAW WDM 24-23-21 FOR TROUBLESHOOTING. ADDITIONAL BITE TEST OF BPCU & NR 2 GCU PERFORMED AFTER ENGINE RUNS & PWR XFERS. NO DEFICIENCIES NOTED. IAW FIM 24-21 TASK 801, & AMM 24-41-21-400-801.