As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI AC VOLT/FREQ SELECTOR SWITCH ON OVHD PANEL STARTED TO SMOKE. WHEN RIGHT SELECTED VOLTS/FREQS READ ZERO WITH ENGINE RUNNING. SELECTED LEFT SMOKE STOPPED. RTB. FOUND VOLTMETER/AMMETER SELECT SWITCH BURNED AND SHORTED. REPLACED SAME. ALL OK. ACFT OK FOR SERVICE.