As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR RETURN DUE TO EMERGENCY POWER PROBLEM. LOST EMERGENCY POWER AFTER TAKEOFF. VOLTAGE WAS NORMAL. LOST STANDBY HORIZON AND COM 1. MAINTENANCE REMOVED AND REPLACED EMERGENCY POWER SUPPLY (P/N 501-1712-02) (S/N ON 1679) (S/N OFF 4585) PER SAAB AMM 24-35-10-4. OPS CHECK GOOD.