We have DSR-80. For future generations, Error Msg 09-821 means "Failed to complete unthreading within the specified time."
Sony tech told me the system timed out due to non-operation of the threading mechanism. Sony said it sounds as if the system is jammed, or the threading motor is bad, or the driver system (frequency generator) is defective. I told the tech that, using Left-Arrow + Menu button > Motor Check > Threading has the message, "TH FG NOT EXIST. FG stands for frequency generator.
Remove the transport, remove the winding motor (two screws) – taking it away from the optical coupler, then see if the motor runs using the Left-Arrow + Menu or from a 9-volt battery. If it does run, the Frequency Generator is bad and the DSR-80 needs to go to Sony. The motor assembly can be purchased as a part. The tech said that sometimes the idler or threading arms can jam under the threading turntable mechanism. Otherwise, the unit has to be sent to Sony for repair.
I hope this helps some. Don't try anything beyond your expertise -- that can get more expensive!
