April 6, 2011

'Unlock' Modifications for ICOM, Kenwood transceivers

These modifications will "unlock" the transmit function on ham radio transceivers, so that they will transmit OUTSIDE of the amateur radio bands, rather than being restricted to those bands. This of course makes them ideal for use by shortwave pirate radio station operators. (This information was scraped from a website that no longer exists in its former form. I make no claim as to the accuracy of these modifications-- use at your own risk!)

These modifications "unlock" the transmitter sections of these transceivers, turning them into "general coverage" shortwave transmitters on the transmitter side.

Mods for:  Icom 735, 720, 745, 751, 430, 940, 440, 2600 ht

To unlock the transmitter: cut diodes D33 and D34 that are standing on
end near the microprocessor section toward the rear top of the radio.

Transmitter is unlocked by snipping the light blue wire that's at the
very end of the top hatch cover to the left middle side of the

Locate the RF board on the side of the radio and cut the light brown
wire at jack 7., which is going to pin 1. Your transmitter is now

Locate the RF board on the side of the radio and cut the black wire
going to pin 1 of jack 2. Your transmitter is now unlocked. (This
mod also described in _73_, July 1985 p. 12.)

Locate the two diodes standing on end with Teflon covering the top
part of their leads (which at one time were soldered together, broken,
and then resoldered). Simply clip these two leads to unlock the
transmitter, but be sure to reset the microprocessor by pushing the
reset button before the set is capable of transmitting on any
frequency at 150 MHz.

Unplug 3-wire plug on the RF board that mates with socket 10. When
looking at the top front of the radio, it's to the left front side
right beside a larger white plug. You'll need to carefully examine
the circuit board and locate the number 10 with a circle around it to
insure you have the right plug.

Locate IC number 109. Now find diode 130 and cut it for all-band
transmit. If you want just MARS coverage, locate IC 111 and 112, and
snip diode 135 beside it.

West,Gordon: "Kenwood 440 Modifications" _Popular Communica-
tions_, October 1987 p. 62.

Illustration captions:
1. Remove 17 screws holding on the bottom and top covers. The bottom
cover comes off, and the top cover is carefully removed and put next
to the radio. It is till connected via the speaker wire.

2. Gain access to the front of the unit by removing two top side
screws and loosening two bottom side screws. This allows the front
assembly to swing open.

3. Remove the shiny silver control board protection plate. This
requires removing two screws on the top and three screws on the
bottom. Lift the plate out completely.

4. Locate diode D-80 in the bottom left-hand corner. Snip it for
all-band transmit.

5. Now locate D-66 and snip. It adds 10 Hertz readout to your
digital frequency display.

6. Carefully reassemble the control plate using a magnetized tiny
screwdriver to hold the five tiny screws in place. Don't pinch any
wires. Also, close up the front and replace the top and bottom covers
with 17 screws.

7. Connect power. Depress A=B switch and turn on the power
simultaneously. This resets the microprocessor for all-band transmit
and 10 Hz frequency display.

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