As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI OUT, R GEN OFF EICAS MESSAGE APPEARED WITHIN 1-2 SECONDS OF TAKEOFF POWER APPLICATION. A/C ABORTED TAKE OFF (ATO) AND RETURNED TO GATE (BTB). MTX GROUNDED A/C AND TROUBLESHOT. REMOVED AND REPLACED R/H GCU IAW AMM 24-22-02. OPS CHECK GOOD. PERFORMED IDLE RUN AND IDG OPS GOOD WITH .51 LOAD IAW AMM 71-00-00. A/C REMAINS NO ETOPS. RETURNED A/C TO SERVICE.