As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT CRUISE ALTITUDE; PVR-ORD, THE LEFT VOR RECEIVER BUTTON WAS PUSHED TO MANUAL MODE. THE UNIT STARTED TO EMIT A LITTLE SMOKE. THE QRH PROCEDURE WAS FOLLOWED AND THE SYSTEM WAS ISOLATED. BUTTON WAS PULLED OUT AND THE CIRCUIT BREAKER WAS PULLED AND THE SMOKE STOPPED. REMOVED AND REPLACED THE LEFT VOR DME CONTROL PANEL. OPS CHECKED GOOD.