As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PREFLIGHT AFTER BATTERIES AND AVIONICS WERE TURNED ON, F/O NOTED SMOKE COMING OUT OF THE AVIONICS VENT. SMOKE HAD A STRONG ELECTRICAL ODOR. POWER WAS REMOVED FROM ACFT. R & R NR 2 INTEGRATED NAVIGATION UNIT IAW MM 34-51-00. SYS OPS CHECKED GOOD ACFT OK FOR CONTINUED SERVICE.