The 9825 tape drive is very similar (mechanically) to the HP-85
tape drive, so the following link will give you a couple of hints.
http://www.series80.org/Articles/capstan-repair.html
I mainly use the first method (suggested by Katie) and I have had
very good and consistent results.
BTW if you click on the pictures you get larger versions.
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Be VERY carefull when disassembling the drive, do not remove the
screws that hold the top (black) cover to the base of the tape
drive, there are a couple of little parts (plastic balls, I think)
that will run away. The first time I took an HP-85 apart, I spent
a lot of time hunting these damn parts.
Anyway, you should be able to remove the capstan and motor assembly
without taking the rest of the drive apart. You may need to unsolder
the two little tachometer wires (but in some cases they are simply
inserted into the PCB).
Good luck
**vp