As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING BOARDING SEVERAL CIRCUIT BREAKERS POPPED AND MULTIPLE AMBER LIGHTS ON OVERHEAD ILLUMINATED; SMOKE FILLED THE COCKPIT; ORDERED A/C EVACUATED; POWERED A/C DOWN. REPLACED APU GENERAL CONTROL UNIT DUE TO FAILURE IAW MM 24-21-81; CHANGED APU GENERAL BREAKER PRECAUTIONARY, FOR SIGN IF HIGH TEMP IAW AWA CARD A8M24001.