Actually the DKC-850 works on a MX-100A but I seems to remember
one feature may not work; maybe "Internet radio"?  Yamaha's service
department is at 1-800-854-1569.  I am no longer associated with
Yamaha.

The biggest problem with any electronic player is it's obsolete within
a few years and _no_ parts are available.  The MX100 floppy disk drive
was a standard disk drive at the time.

Don Teach
Shreveport, Louisiana