As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT DECK HAS STRONG ELECTRICAL BURNING SMELL. ACFT GROUNDED. FOUND CAPTAIN'S FMCS CONTROL UNIT TO BE THE SOURCE OF ELECTRICAL SMELL. PULLED AND TAGGED 1 C/B. REMOVED AND REPLACED #1 FMCS CDU. RESET 1 C/B. OPS TEST GOOD. SOFTWARE CONFIRMED APPLICABLE. REF B737-800 AMM 34-61-01 AND APIC 34-61-01-03.