So I'm still chasing this problem. I found on ebay a used drive but the p/n is slightly different. It's an ADU 20F 1X D (1991 date), whereas mine is ADU 20F 1X E (1993 date). Would the earlier version likely work? Physically they look the same. My other option is to send mine for rebuild but I can't take the machine out of service for two weeks at the moment.