What was found
(CAN) CHANGED (DISTANCE MEASURING EQUIPMENT) DME FREQUENCY AND IT WASN`T SHOWING A READOUT. T\AS THEY LOOKED THE READOUT APPEARED THEN NOTICED PART OF READ OUT FLASHED VERY BRIGHT AND THE REST VANISHED. ALMOST IMMEDIATELY, CO-PILOT STATED THEY COULD SMELL ELECTRICAL SMOKE. PILOT LOOKED AT DME AGAIN AND COULD SEE SMOKE STARTING TO BILLOW OUT. IMMEDIATLY TURNED OFF UNIT, BUT SMOKE DID NOT STOP. TURNED OFF THE AVIONICS MASTER WHILE COPLIOT LOCATED CB AND TURNED AVIONICS BACK ON. SMOKE STOPPED. DEFERRED IAW MEL 34-14 PLACARD INSTALLED.