As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 2786, PILOT REPORT SMOKE IN COCKPIT AFTER SELECTING PACKS AT 500' AGL. ACFT RETURNED TO FIELD. MTX PLACED NR 1 PACK ON MEL AS PER MEL 21-51-00 CAT C, CONTROL NR 059007 AND WAS RELEASED. NR 1 ACM WAS REMOVED AND REPLACED UPON ACFT'S ARRIVAL INTO CLE, MEL WAS CLEARED AND ACFT WAS RELEASED TO SERVICE.