

                 <<< ICOM IC-228E/IC-228H >>>

FREQUENCY COVERAGE MODIFICATION 144 - 146MHz => 138 - 174MHz
 
                   April 9th 1990 by OH3NWP
 
===================================================================
 
Follow steps one after another CAREFULLY.
 
 1) Turn power OFF and disconnect the power cable from the trans-
    ceiver.
 
 2) Remove 2 screws from the top cover and open it.
 
 3) Remove 2 screws from the bottom cover and open it slowly.
    Disconnect speaker connector from RX UNIT's connector J3.
 
 4) Remove 4 screws from the front panel (2 on left and 2 on right
    side).
 
 5) Turn front panel opened slowly.
 
 6) To expand RX frequency coverage cut diode D19, that is located
    on top edge of the EF UNIT (hidden side of the front panel).
 
 7) If you don't need expanded TX coverage, jump to step 13.
 
 8) Disconnect the gray double cable coming from EF UNIT to RX UNIT
    plug connector J6. You will get free space for solder iron.
 
 9) Disconnect (soldered) '+'-end of the memory backup lithium
    battery and carefully swing the battery to upright position.
    Battery is fixed on EF UNIT with a sticker.
 
10) Find the microprocessor. It's located in the middle of the
    PC board. Find a component place for diode D7, that is located  
    about 10 mm left of the 5th pin in the left edge of the
    microprocessor:
 
                                            _I__I__I__I__I__
                                          --I
                                          --I
                      PIN_1               --I   micro-
    diode D7 =>       o                   --I   processor
                    o   o        (5th pin)--I
               in this place. In USA/Asia model IC-228A there is a surface
   
12) Add a diode between PIN_2 (anode) and PIN_1 (cathode).
    USE NARROW SOLDER IRON TO AVOID SHORT CIRCUITS ! ! !
    In eur13) OK, the modification has been done. Now foll15) Reset the microprocessor. Press SQL/MONITOR and LOCK buttons
    for RX is 138 - 174MHz, and if diode D7 added, TX coverage is
    the same.
 
That's it.
 
<<< 73's de Jussi/OH3NWP/OH7DC >>>
