As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PERFORMED AN AIR TURNBACK DUE TO AN ELECTRICAL BURNING ODOR THROUGHOUT THE ACFT. FOUND CIRCUIT BREAKER POSITION F6, LEFT ADF, WAS TRIPPED. VERIFIED THE ADF RECEIVER AS THE CAUSE. REPLACED THE LT ADF RECEIVER IAW AMM 34-57. INSPECTED ACFT CARGO BIN AND E/E COMPARTMENTS FOR OTHER PROBLEMS, NONE FOUND. ACFT OK FOR SERVICE.