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Icom IC-725 (IC 725 IC725) MARS modifications
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DISCLAIMER:
This modification allows the radio to transmit outside of the designated
Amateur freq. Transmitting where you are not licensed to do so is
unlawful!
Disassemble radio following instructions on page 24 of Instruction
manual, steps 1 - 7, or as follows:
NOTE:
All instructions with the radio's front panel facing you unless
otherwise specified!
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Remove all black screws from top & bottom covers and remove both covers.
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Remove the 2 flat head screws that hold the PA unit to the front unit.
(top front of radio - Not the screws that are in the plastic front panel.)
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Remove the 2 screws that hold the PA unit to the rear panel.
(Looking at the rear of the radio, 1 is above the ext. speaker jack &
1 is above to ACC(1) jack.)
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Unplug the 2 plugs from J11 & J12.
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D
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Disconnect the large black connector on the left side of radio.
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Slide up and out, the TUNER CONTROL SOCKET from it's holder in the rear
panel.
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Remove the tape from the right side of the PA unit.
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Swing the PA unit up to the left and lay over flat.
located to the left side, rear of the board, next to J4.
You may have to remove J4 to allow access to D-5.
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Reassembly is As if you were opening a book! You now have the PLL unit exposed.
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Cut Diode D-5 from the PLL unit.
D-5 is loca reverse of above.
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The radio will now transmit from 1.5 MHz to 33 Mhz. (It will transmit
even lower but the power output drops off and I don't know if doing so
will damage the transmitter.
ENABLE PREAMP Bve bottom cover.
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Locate Q12 on Main Unit. 1/3 way from left side of board.
Q12 is the transistor that bypasses the preamp below 1.5 MHz
to avoid overload when listening to AM Broadcast Stations.
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Clip the lead of Q12 closest the front of the radio.
That's it, the preamp will now work below 1.5 MHz!
ENABLE NOISE BLANKER IN ALL MODES
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Remove bottom cover.
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Locate R44 on Main Unit (100 ohm 1/4 watt resistor).
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Lift the side of R44 closest the front of the radio.
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Solder a piece of wire to the end of R44 that you lifted.
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Solder the other end of the wire to W54 which is located near the left
side of IC15.
This will supply a constant 8 Volts lly the 8 Volts is only present
when in CW or SSB Modes, disabling the noise blanker in AM & FM modes.
I have done all of the above mods to my own 725 and they work great!
These mods should also work with the IC-726.
I'll let everyone know for sure when I get one!
Preamp and Noise Blanker Modifications courtesy of N1FCJ
P.S.
If you have any good modifications for any radios, please pass them
along to me. I am starting a database of modifications for various
radios and I'm happy to pass along info to anyone who needs it.
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