New LCD Readout for Kenwood TM-721A
             
             
     I just replaced the LCD readout on the TM-721A and thought you may be
interested in my experience.  The replacement is easy and gives the desired
result: the readout is easy to read in high ambient light.  The TM-621A can be
upgraded with the same unit.

     I ordered the unit from Kenwood amateur equipment division parts
department which you can call at (213) 639-7140 (639-4200 and 639-9000 are 
alternate phone numbers I have seen on the PBBS board) and order part number
B38033705, or just ask for the LCD conversion for the TM-721A.  The price is
$37 plus California state tax and S&H, which came to $43.50.  They will take
credit card charge over the phone.

     What you get is the complete LCD display unit with its two IC drivers. On
the schematic that comes with your radio you can identify the subassembly as 
the one labeled "LCD ASS'Y" which is connected to the control unit by an 8-
conductor ribbon cable, which you must unsolder to free to old unit and 
resolder for the new one.  The LCD subunit is attached to the control unit
assembly by bent tabs which are easily undone. The ribbon cable comes with a
small section of pressure-sensitive adhesive to help position it for
soldering.  Complete step-by-step instructions come with the unit.
Installation requires a small soldering iron and is not difficult. 

     The results are quite good: there is no functional difference in the way
the radio operates.  I suspect that the new LCD is electrically identical to
the old.  If you have modified your radio to operate as a cross-band repeater,
you retain that function.  The display consists of black digits on a milky-
white background.  The incandescent lamps behind it operate as before, and I 
find that even in the "dim" mode that the legibility is good in low light. In
bright sunlight, the back illumination is no longer relevant, and the
readability is very good.  Since bright lamp operation is not really required,
they should last forever.

     The old unit is not destroyed upon removal.  You can return to the old
readout at any time (which is prettier as it is in color). Kenwood is to be
congratulated for recognizing the problem with a large installed base of TM-
721A's and making this field fix available.

     While you have your radio open, you may want to activate the cross-band
repeater function.  Lay the CPU board down so the two ribbon cables come off
to the north.  A little northeast of the lithium cell, just east of the bare
copper landing at the top of the board is chip resistor R121.  Carefully
remove it (you will probably break it).  Now, you can put your radio in the
cross-band repeater mode by hitting "f" "ABC".  The mode is indicated by three
decimal points in both main and subband frequency readouts and a signal heard 
on either band is retransmitted on the other.  A three minute timer is in
effect, which may be turned off by removing R122 (not tested).  Return to 
normal operation by again hitting "f" "ABC".  During repeater operation, all
other functions are locked out.  Of course, the TM-721A does not auto-
identify, so it must be under direct operator control.

John, W6BM @ W6PW, in Berkeley