138 lines
7.4 KiB
Modula-2
138 lines
7.4 KiB
Modula-2
05/20/90
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This document describes the steps in enabling out of band
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transmit to the Kenwood 231A 2 meter transceiver. This
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modification will allow transmit throughout the 136.000 to
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173.995 Mhz range. I do not condone, authorize or any way
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promote illegal out of band communication. More than likely,
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performing this modification will void the warranty, also no
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guarantees are made and you are at your own risk. In other words,
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don't blame me if you kill your radio! Please read all of text
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before deciding or continuing. Also performing either the
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MARS/CAP mod or the full extended transmit mod will erase the
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memories.
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First of all you should be aware that this modification
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disables the automatic ARRL transmit offset feature. Second, if
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you do not feel comfortable taking your radio apart, soldering to
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a surface mount board,or working with very small items, please
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find someone who can help you.
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Ok, now with all that out of the way, here we go. You will
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need:
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a VERY small soldering iron with a tip no larger than about a
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sixteenth of an inch, a phillips screwdriver, a pair of VERY
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small tweezers or forceps, some very thin solder, a 1N914, or
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similiar glass diode (NOTE: if you have a chip diode of similiar
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rating, all the better!), a small box to put all the tiny parts
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in. Also a small vise or circuit board
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holder and a pair of external snap ring pliers are helpful. At
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this time it would be a good idea to write down the memories on a
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piece of paper, as doing the mod erases the memories. Disconnect
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the microphone, power, and antenna.
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MAKE SURE NO POWER IS CONNECTED TO THE RADIO!
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1) Take the radio apart --- Remove the 4 black phillips head
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screws from the top and bottom black metal shields, put them in
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the small box so as not to lose them. Remove the two metal covers
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and put them aside.
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Note: If you just want to mod the radio for MARS/CAP, just remove
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the top cover and clip the GREEN wire just above the VFO,MR,MHZ
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switches, and replace the top cover. This extends transmit about
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3 Mhz on either side of the ham band.
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Place the radio on a pad or soft STATIC free work area. Looking
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at the front of the radio, you will see how the black face plate
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is held in place by 4 little plastic keepers that run over metal
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bumps in the sub-frame. By GENTLY inserting your finger nail and
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pushing each keeper, you will be able to remove the face plate,
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be careful, its plastic. Pull the volume, squelch and frequency
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selector knobs off, the freq. selector is a real bear, but a
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strong steady pull will remove it. Next, using a pair of pliers
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or a set of external snap ring pliers, remove the mic connector
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ring nut from the mic connector, now remove the nut that is on
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the freq. selector. Again put all the parts in the small box.
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Gently remove the LCD assembly from the radio. You will see a
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series of silver springs mounted horizontaly on the back of the
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LCD assembly, these mate with short silver pins on the cpu board.
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Put the LCD assembly aside in a safe STATIC free place. The next
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step is to remove the metal shield that covers the cpu board. Do
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this by removing 4 screws, two are located on the short sides and
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the other two are located on the top and bottom of the radio. Put
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the screws in the small box for safe keeping. Gently remove the
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metal plate from the radio and put it aside. Finally the cpu
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board must be removed. If your radio has the CTCSS encoder
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and/or the DRU voice recorder, you must remove these before
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continuing. Consult the manual and reverse the installation
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procedures to remove them. Be careful when pulling the small
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white multi pin connectors, forceps work the best. There are 3
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screws that hold the cpu board on to the radio frame. Two are
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located to the right of the frequency selector and the third is
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located near the squelch control. Also there are two multi pin
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connectors located at the bottom of the backside of the cpu board
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that connect to the rf portion of the radio. Remove the 3 screws
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making sure not to drop them on the board. (Remember the battery
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backup!) Now using your thumbs at the bottom, and your fore
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fingers at the top of the board, gently disconnect and remove the
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cpu board. Be careful in handling the board as it contains many
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static sensitive components. Always hold the board by the sides
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as to not touch any traces or pin leads. If you have a small
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vise or circuit board holder, place the board in it, solder side
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up, so the row of switches (Call, F, Shift, Tone, Rev, Drs) are
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pointing toword you.
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What needs to be done, is to solder a diode to the pads
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located under the tone switch. (S205) This is D209 on the
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schematic. Note that Kenwood calls the radio with this diode
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installed a -21 version, for use in "other areas". You will
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probobly notice how small and how thinly spaced the pads are, and
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you will be wondering how that BIG diode is going to fit!...
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2) Making the mod --- If you have a chip diode that will fit,
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skip this part. Otherwise, like me, you will have to fabricate
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your own SMT diode. Do this by bending the leads of the diode
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under the body and clipping the remaining lead lengths so that
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space between the leads are equal to the spacing of pads on the
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board. THE DIODE MUST BE POSITIONED SO THAT THE CATHODE IS
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POINTING DOWN, TOWORD THE CPU CHIP. THIS IS VERY IMPORTANT.
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Try making about 5 of these guys, taking each one and visually
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fitting it to the pads. Look at the overall height compared to
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the height of the connectors. Also look at the pad spacing, a
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magnifiying glass works well unless you have eyes like a
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microscope. Once you've selected the best one, tin the leads of
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the diode so just a quick tap of the hot soldering iron will
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"plant" the part on the pads. Now, holding the diode in the
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proper orientation, tack down one lead, (hopefully you didn't
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drink too much coffee this morning!), then, using the tweezers
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orient the other lead and tack it down with the soldering iron.
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You shouldn't need any additional solder, just the solder on the
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pad and the tinning on the diode leads. Using the magnifiying
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glass, FULLY INSPECT THE CONNECTION, making sure there are no
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solder bridges and that the diode is positioned properly with the
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cathode pointing toword the cpu. Once you are satisfied proceed
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with step 3.
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3) Button it up --- Reverse the take down procedure to put the
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radio back together. Attach the cpu board by aligning the
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connectors on the back, press firmly to engage the connectors,
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insert the 3 screws and tighten, remember the radio frame is
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aluminum, so don't strip them out. Attach the metal sub frame
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using the 4 screws. Gently place the LCD sub assembly on top and
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hold it in place so the little springs make contact while you
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attach the microphone connector ring nut and the freq. selector
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nut. Tighten them down. Press the plastic face plate so that
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the little keepers "snap" over the bumps. Re-attach the CTCSS
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and/or DRU if applicable. Replace the top and bottom black covers
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with the four screws. Check the small box and make sure you
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don't have any "spare" parts.
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That's it, just connect power, antenna and the microphone.
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Turning on the power will reset the radio erasing all memories.
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Oh well...
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Good luck and 73,
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Paul Saffren --- N6NHH
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@KI6EH
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