Media Share 9/MEDIASHARE_09.ISO/hamradio/kenwood1.zip/TM231.MOD

Text File | 1990-06-04 | 7KB | 123 lines

                                                         05/20/90
This document describes the steps in enabling out of band transmit
to the Kenwood 231A 2 meter transceiver. This modification will allow
transmit throughout the 136.000 to 173.995 Mhz range.  I do not condone,
authorize or any way promote illegal out of band communication.
More than likely, performing this modification will void the warranty,
also no guarantees are made and you are at your own risk. In other
words, don't blame me if you kill your radio!  Please read all of text
before deciding or continuing.  Also performing either the MARS/CAP
mod or the full extended transmit mod will erase the memories.

   First of all you should be aware that this modification disables the
automatic ARRL transmit offset feature.  Second, if you do not feel
comfortable taking your radio apart, soldering to a surface mount board,
or working with very small items, please find someone who can help you.

   Ok, now with all that out of the way, here we go.  You will need:
a VERY small soldering iron with a tip no larger than about a sixteenth
of an inch, a phillips screwdriver, a pair of VERY small tweezers or
forceps, some very thin solder, a 1N914, or similiar glass diode (NOTE:
if you have a chip diode of similiar rating, all the better!), a small
box to put all the tiny parts in.  Also a small vise or circuit board
holder and a pair of external snap ring pliers are helpful. At this time
it would be a good idea to write down the memories on a piece of paper, as
doing the mod erases the memories.  Disconnect the microphone, power,
and antenna.

          MAKE SURE NO POWER IS CONNECTED TO THE RADIO!

   1) Take the radio apart --- Remove the 4 black phillips head screws
from the top and bottom black metal shields, put them in the small box
so as not to lose them. Remove the two metal covers and put them aside.

Note: If you just want to mod the radio for MARS/CAP, just remove the
top cover and clip the GREEN wire just above the VFO,MR,MHZ switches,
and replace the top cover. This extends transmit about 3 Mhz on either
side of the ham band.

Place the radio on a pad or soft STATIC free work area.  Looking at the
front of the radio, you will see how the black face plate is held in
place by 4 little plastic keepers that run over metal bumps in the sub-
frame.  By GENTLY inserting your finger nail and pushing each keeper,
you will be able to remove the face plate, be careful, its plastic. Pull
the volume, squelch and frequency selector knobs off, the freq. selector
is a real bear, but a strong steady pull will remove it. Next, using a
pair of pliers or a set of external snap ring pliers, remove the mic
connector ring nut from the mic connector, now remove the nut that is on
the freq. selector.  Again put all the parts in the small box.  Gently
remove the LCD assembly from the radio.  You will see a series of silver
springs mounted horizontaly on the back of the LCD assembly, these mate
with short silver pins on the cpu board.  Put the LCD assembly aside in
a safe STATIC free place.  The next step is to remove the metal shield
that covers the cpu board.  Do this by removing 4 screws, two are located
on the short sides and the other two are located on the top and bottom of
the radio. Put the screws in the small box for safe keeping.  Gently
remove the metal plate from the radio and put it aside.  Finally the cpu
board must be removed.  If your radio has the CTCSS encoder and/or the
DRU voice recorder, you must remove these before continuing.  Consult
the manual and reverse the installation procedures to remove them.  Be
careful when pulling the small white multi pin connectors, forceps work
the best.  There are 3 screws that hold the cpu board on to the radio
frame. Two are located to the right of the frequency selector and the
third is located near the squelch control.  Also there are two multi pin
connectors located at the bottom of the backside of the cpu board that
connect to the rf portion of the radio.  Remove the 3 screws making sure
not to drop them on the board.  (Remember the battery backup!)  Now using
your thumbs at the bottom, and your fore fingers at the top of the board,
gently disconnect and remove the cpu board.  Be careful in handling the
board as it contains many static sensitive components.  Always hold the
board by the sides as to not touch any traces or pin leads.  If you have
a small vise or circuit board holder, place the board in it, solder side
up, so the row of switches (Call, F, Shift, Tone, Rev, Drs) are pointing
toword you.

    What needs to be done, is to solder a diode to the pads located under
the tone switch. (S205)  This is D209 on the schematic.  Note that Kenwood
calls the radio with this diode installed a -21 version, for use in
"other areas". You will probobly notice how small and how thinly spaced
the pads are, and you will be wondering how that BIG diode is going to
fit!...

   2) Making the mod --- If you have a chip diode that will fit, skip this
part.  Otherwise, like me, you will have to fabricate your own SMT diode.
Do this by bending the leads of the diode under the body and clipping the
remaining lead lengths so that space between the leads are equal to the
spacing of pads on the board. THE DIODE MUST BE POSITIONED SO THAT THE
CATHODE IS POINTING DOWN, TOWORD THE CPU CHIP.   THIS IS VERY IMPORTANT.
  Try making about 5 of these guys, taking each one and visually fitting
it to the pads.  Look at the overall height compared to the height of
the connectors.  Also look at the pad spacing, a magnifiying glass works
well unless you have eyes like a microscope.  Once you've selected the
best one, tin the leads of the diode so just a quick tap of the hot
soldering iron will "plant" the part on the pads. Now, holding the diode
in the proper orientation, tack down one lead, (hopefully you didn't
drink too much coffee this morning!), then, using the tweezers orient the
other lead and tack it down with the soldering iron.  You shouldn't need
any additional solder, just the solder on the pad and the tinning on the
diode leads.  Using the magnifiying glass, FULLY INSPECT THE CONNECTION,
making sure there are no solder bridges and that the diode is positioned
properly with the cathode pointing toword the cpu. Once you are satisfied
proceed with step 3.


  3) Button it up --- Reverse the take down procedure to put the radio
back together.  Attach the cpu board by aligning the connectors on the
back, press firmly to engage the connectors, insert the 3 screws and
tighten, remember the radio frame is aluminum, so don't strip them out.
Attach the metal sub frame using the 4 screws.  Gently place the LCD
sub assembly on top and hold it in place so the little springs make contact
while you attach the microphone connector ring nut and the freq. selector
nut.  Tighten them down.  Press the plastic face plate so that the little
keepers "snap" over the bumps.  Re-attach the CTCSS and/or DRU if applicable.
Replace the top and bottom black covers with the four screws.  Check the
small box and make sure you don't have any "spare" parts.

  That's it, just connect power, antenna and the microphone.  Turning on
the power will reset the radio erasing all memories.  Oh well...

                         Good luck and 73,

                       Paul Saffren --- N6NHH
                       @KI6EH