copied from the Internet:
Newsgroups: rec.radio.amateur.misc
Subject: Kenwood TM-941A UNDOCUMENTED FEATURE

Documentation follows....

This modification is not really a modification, but an
undocumented feature that Kenwood Corporation has no record of.
This modification has not been completely tested, so those who
feel brave enough to try this out are welcome to it, but I am not
responsible for any ill-effects as a result of utilizing this
feature.

What this feature offers to the end-user is an extremely powerful
feature: doubling your memory capacity.  With the Kenwood TM-941A,
the radio has ONE VFO, ONE CALL, and 100 memory positions that are
labelled 00 thru 99.  This feature offers the user another
100 memory positions PER BAND!!!

How to perform this undocumented feature:

1.  Have the radio turned on.
2.  Press F and REV simultaneously.
3.  Memory position A1 will show; this memory position cannot be
    eliminated thru the MR/F function.
4.  Work the VFO in a similar manner that you would with the
    radio in normal mode.
5.  When you save the memory position, take a look around at the
    layout of these memory positions -- the memories are labelled
    hexidecimally; that is, they are labelled AA thru A9,
    B0 thru B9 until you have reached J9.  J9 is the 100th
    position in this alter memory area.
6.  When you are finished, just press the F and the REV buttons
    simultaneously, and you are back in the normal memory area.

As stated before, this feature has been found to be static in
nature; that is, when the power is turned off, the memory
positions are still retained and do not interfer with the
original memory area.  Mind you, this memory feature has not
been completely tested, SO BE EXTRMELY CAREFUL!  I ASSUME NO
LIABILITY FOR FINDING THIS FEATURE SINCE I AM DOING THIS AS A
BENEFIT TO AMATEUR RADIO!

BTW, Kenwood does not have any records and/or any comments
regarding this feature.  I suspect that this feature is for
diagnostic purposes and should be treated as such.
Forewarned is forearmed!

Enjoy and 73!  :-)
-- 
Robert S. Radvanovsky 
Note: I haven't tried or verified this, proceed at your own risk.  WA2ISE

Addendum--

After speaking with Bob KC6ONL, he received another message from a ham
who also has a TM-941A and could not duplicate the keyboard memory mod.
It could be that the mod can only be applied to certain serial numbers
but could not be certain.