As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB SPARKS AND SMOKE EMITTED FROM THE AREA OF THE NR 1 START SWITCH. LOW IGNITION CB POPPED AT WHICH TIME THE SPARKS AND SMOKE CEASED. FLIGHT CREW RETURNED TO THE DEPARTURE AIRPORT FOR AN UNEVENTFUL LANDING. REPLACED SWITCH DUE TO ARCING ON CASE AND REPAIRED WIRING. INSPECTED OTHER AIRCRAFT IN FLEET NO OTHER CHAFED WIRES FOUND IN VICINITY OF THE START SWITCHES.