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ICOM IC-32AT Out of Band Mod [message #3075] Sun, 08 March 2015 22:23
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Registered: December 2004
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This mod allows the unit to RX-TX outside both ham bands, plus function as a cross-band repeater! BE CAREFUL THAT YOU DON'T INADVERTENTLY TRANSMIT!

DIS-ASSEMBLY

1. Remove the battery.
2. Loosen but do not remove the two screws holding the PTT switch plate.
3. Remove the 4 screws on the back of the radio.
4. Now remove the front of the HT by carefully lifting the bottom edge and then pulling it down so it clears the top of the HT. Be carefull as there is a ribbon cable attached.
5. Unplug the Speaker/Mic plug from the main chassis to allow the front conver to be fully opened.

MODIFICATION (Refer to figure 1.)

1. Remove D907
2. Remove D913
3. Move D912 down to next pad. (D???, bottom location)
4. Add diodes Da and Db (1N914 or Equiv.)

VCO ADJUSTMENT

1. Unplug and remove the PTT/FUNCTION circuit board and lay it aside.
2. Remove the top circuit board by removing the screws located in each corner of the board. These are the ones that are recessed and not the ones on top of the board.
3. Carefully pry up the circuit board until it can be folded out. Plug in the PTT/Function button circuit board cable.
4. Hook up the battery and reset the CPU by holding down the "Function" and "A" buttons and cycling power off and on.
5. On the bottom circuit board are located the two VCO's (refer to figure 2). The left hand VCO is for VHF and the right hand VCO is for UHF. Located just to the left of the UHF VCO is a resistor standing on end. Hook the V. O. M. positive lead to the top of this resistor. The negative lead goes to ground.
6. Under aluminum tape on each VCO is the adjustment point. Normally, the VHF VCO will not require adjustment. The VHF adjustment is L554, the UHF adjustment is C510. Adjust the desired VCO for a +.5vdc reading for the lowest frequency you wish to tune on that band. Don't forget to re-tape the holes on the VCO's.
7. Disconnect the battery and carefully reassemble the radio. DON'T PINCH ANY WIRES!


CROSS-BAND REPEATER COMMANDS
1. Enter one VHF and one UHF frequency into each VFO. (Offsets won't work.)
2. To enable cross-band repeater, hold down "FUNCTION" button and key in, [C] [6] [D]. Then release "FUNCTION" button.
3. To disable cross-band repeater, wait until handheld is in receive only and then hold down "FUNCTION" button and key in, [D] [C]. Then release "FUNCTION" button.


*** Once handheld retransmits a signal from opposite band you cannot disable cross-band function until squelch closes and handheld quits transmitting! ***

Figure 1

.--------------------------------------------------------------------
l                             .     .------------DIODE-Da--------.  l
l                       D915 +-+  ['] D909                       :  l
l                             .     .------------DIODE-Db--------+  l
l                       D916 [ ]  ['] D910                       :  l
l                             .    .                             :  l
l                       D917 +-+  +-+ D911                       :  l
l        .----------------------------------------.              :  l
l        l            .-----------.               l              :  l
l        l          .'             ';             l              :  l
l        l        .'                 ';           l              :  l
l        l        :      BACK OF      :           l              :  l
l        l        :      SPEAKER      :           l  +--+      +-:+ l
l        l        '.                 .'           l  :  :      : ': l D907
l        l          '.             .'             l  +--+      +--+ l
l        l            -------------               l                 l
l        l                                        l  +--+      +--+ l
l        l  Removing this diode results in -----> l  : --REMOVE-- : l D913
l        l  expanded UHF coverage from            l  +--+      +--+ l
'--------'  400 - 479 MHZ.                        l                 l
                                                  l  +--+      +--+ l
                                                  l  :  :      :  : l D908
                                                  l  +--+      +--+ l
                                                  l                 l
                                                  l                 l
                                                  l  +--+      +--+ l
            Removing this diode results in -----> l  : --REMOVE-- : l D912
            enabling the unit as a cross-         l  +--+      +--+ l
            band repeater.                        l                 l
                                                  l  +--+      +--+ l
                                                  l  : --DIODE--- : l D???
                                                  l  +--+      +--+ l
                                                  l                 l
                                                  ------------------'

FIGURE 2

.------------------------------------.
l            .----------.            l
l            :          :            l
l            :          :            l
l            : PA CHIP  :            l
l            :          :            l
l            :          :            l
l            '----------'            l
l   .----. Attach V.O.M.    .----.   l
l   :    : meter lead --> O :    :   l
l   : () :                  : () :   l
l   :    :                  :    :   l
l   :    :                  :    :   l
l   '----'                  '----'   l
l   VHF VCO                 UHF VCO  l
'------------------------------------'
               Bottom


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