As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE LINING UP FOR T/O, MASTER WARNING LIGHTS WENT OFF ALONG WITH FMC DISCREET LIGHT AND F/O FMS CDU BLANKED. SHORTLY AFTERWARDS A BURNING ELEC SMELL WAS IN CABIN AND FLIGHT DECK. A/C RTB AND CONTRACT MTC FOUND RT FMS COMPUTER BURNED UP. MTC REMOVED COMPUTER, ALLOWED TO VENT AND COOL DOWN. RE-INSTALLED COMPUTER AND DISPATCHED WITH RT FMC INOP WITH C/B'S PULLED