As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RT FMC OVERHEATED SHORTLY AFTER DEPARTURE. A HOT PLASTIC SMELL WAS VERY EVIDENT IN THE COCKPIT. CAPT ELECTED TO RETURN TO IAD. RT FMC HMCDU OVERHEATED, HOT PLASTIC SMELL WAS VERY EVIDENT IN THE COCKPIT. RT HMCDU BECAME INOPERATIVE AND WAS VERY HOT TO TOUCH. REPLACED THE RIGHT HMCDU. SHOP FINDINGS: BURNED TRACE ON THE I/O CARD A5. SHOP REPORTED PREVIOUS HMCDU'S WITH OVERHEATED CARD A5.