Call the ICOM parts department and order a pair of
MA133 diodes (P/N 1790000850). These are the three terminal surface
mount diode packages. It is probably not advisable to substitute
conventional leaded glass diodes here due to size restraints.
¦ ¦ ¦
¦ +-->|----->|--+ ¦
¦ ¦ ¦ ¦
The modification involves removing one surface mount component and
installing two others. The working parts are extremely small and the
mod should not be performed unless you are comfortable with working
while using a loop eyepiece or other magnifying device. This is a
"surgical" operation. Take all the usual precautions with respect to
static electricity, etc.
Remove 5 screws holding back on, and two screws on side of case below
the PTT switch. Gently pry the unit apart.
Inside the unit are two RF "stack" units. The complete RF "stack" is
composed of two enclosed sheet metal boxes sandwiched together, about
1.5" wide, 2" tall and .5" thick. Each RF stack unit (one per band) is
totally self contained, is about .25" thick, and plugs into the
"motherboard" using connectors mounted on one end.
First, remove the stack units. To do this, remove one screw from each
side of the stack. Remove the single screw off the bottom end of the
stack and gently remove the metal spring clip holding the stack
Carefully lift each stack unit out by pulling it back and down. They
should easily unplug from the upper motherboard. Set them aside for
At this time the back side of the front panel is clearly accessible and
the two CPU's are visible side-by-side across the top. Now refer to
the following illustration:
Top of Radio, Back side of Front Panel
-------- -------- |
| | | | |---
| CPU-1 | | CPU-2 | | |
| | | | | P |
-------- -------- | T |
| T |
-------- | |
.<: <-D1 ---------- |
.. | |fuse | | |
D2-> V ---------- |
D3-> V |
V <-D? |
D1, D2 and D3 are locations on the board. Only D2 is installed
at the factory. To perform the mod, you must do the following:
The locations of D1 and D3 are clearly silk screened onto the circuit
board and are easy to locate. Don't attempt to re-use D2. The periods
(..) show the approximate location of the solder pads for the 2-legged
sides of the diodes.
Diode D2 may be removed by carefully heating the leads and prying it up
using a sharp tool. Be very careful since it's easy to lift the solder
One method of installing diodes D1 and D3 is to use a very small drop
of super glue to mount the part, and then use a soldering iron to tack
down the pins.
After the parts are installed, reassemble the radio. Although the
manufacturer recommends that the microprocessor be reset after this
mod, I have found it to be unnecessary. All memories retained their
settings after the mod. Tests using a dummy load and a frequency
counter showed TX ability on UHF from under 400MHz to over 490MHz.
TX on VHF covers from 136MHz to 174MHz.
Now for the added part - multi-digit entry for mhz
After doing the above, REQUIRED!!
select the VHF band as MAIN
push F (above the PTT button) and SET (the 8 button)
then using the ^/SCAN button make the lower right symbol of the band say PL
rotate the right knob to set the display to 1,10, or 100 as desired
1 sets entry to single digits only
10 sets entry to 10's and single digits
100 sets entry to all digits
Now - repeat the above for the UHF band - Note It WILL NOT work unless you do it for
You now have a walkie that requires all the digits (assuming you chose 100) to program