Hp-41C card reader - dead

[AndiGer]

Hi Marco,
Yes the mentioned thread is one of many touching this problem. Often the coupler is named "clutch". HP65/67/97 card readers suffer the same problem.
If you search the museum (best done by google) after "clutch repair" you will find many threads.
Here is a former one where Randy explains the clutch problem resulting in Checksum Error or in Malfunction: https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=131514
Last year Alberto Fenini posted about a repair approach using the inner part of an antenna cable. He put the pics to his iCloud drive. I can't find the thread now. I didn't try this method but thought it is a very good idea.

In my experience the card not running smoothly is the clutch problem. If you try several more cards to run thru the reader often the clutch will slip more and the motor spins at high speed and the card doesn't move at all.

EDIT: To keep the cover off the reader until you are sure it works fine is a good idea :-)