As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORT SMOKE IN CABIN DURING CLIMBOUT. CLEARED AFTER SHUTTING OFF PACK 1. SMELL OF SMOKE BEFORE BEFORE PACK 1 OVERLOADED AND SHUT DOWN. AIR RETURNED. FLT 4304. CONTRACT MX FOUND ACM SHAFT/BEARINGS DAMAGED AND PLACED ON MEL. 03/29/19 XJT EWR MX REMOVED & REPLACED AIR CYCLE MACHINE IAW 145 AMM 21-51-03.OPS CHECK GOOD. A/C WAS APPROVED FOR RETURN TO SERVICE.