Sorry...this is something YOU CANNOT DO YOURSELF !

The Otari MTR 90 Capstan brushes are soldered in place.... and it requires a lot of
experience to get them out and to install new ones in the capstan motor...

In fact I do NOT even do this myself...

 
I use Athan Corp. in South San Francisco to do this...    
as George has the motor rebuilding experience required and the parts on hand.
http://www.athan.com/index.cgi

 
Please note that any DC motor - ESPECIALLY OLDER ONES - should NOT be taken apart
EXCEPT by an EXPERT....     If you try and do it yourself
you run the risk of immediatly loosing up to 50 % of the Magnetic Strength
of the motor in seconds if you don't use a specialized magnetic flux
retainer ring - correctly sized to the motor and with the proper specifications,
and know how to use one.     Odds are you will just destroy your motor !!!
So use only a Professional Motor rebuilder with experience on capstan Motors !!!
 
 

Soon I'll be posting picture of a Capstan Motor with worn out brushes...   !!!
which DESTROYED the capstan motor completely.






Really... if you've got a well used MTR 90 - with lots of hours on her -
be smart and keep her in great running condition by getting the capstan brushes
replaced by an experienced Capstan rebuilder ASAP...
Otherwise start looking for an expensive replacement capstan motor !!!!