As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE PERFORMING EPSU TEST FOR 2 LT/2 RT DOOR SLIDE REPLACEMENT, FOUND "EPSU O/R (12WL)" FAULT OM MCDU TEST. T/S IAW TSM 33-51-00-810-801-A AND FOUND DEU B 300RHZ BAD. REPLACED DEU B 300RHZ IAW AMM 23-73. OPS CHECK NORMAL. OK FOR SERVICE.