Modifications for the ICOM - RogerK

MODIFICATION (Refer to figure 1.)1. Remove D9072. Remove D913.3. Move D912 down to next pad. (D???, bottom location)4. Add diodes Da and Db (1N914 or Equiv.).VCO ADJUSTMENT1. 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 arerecessed 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 handVCO 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 thetop 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 VHFadjustment is L554, the UHF adjustment is C510. Adjust the desired VCO for a +.5vdc reading for the lowest frequency youwish to tune on that band. Don't forget to retape the holes on the VCO's.7. Disconnect the battery and carefully reassemble the radio. DON'T PINCH ANY WIRES!CROSSBAND REPEATER COMMANDS1. Enter one VHF and one UHF frequency into each VFO. (Offsets won't work.)2. To enable crossband repeater, hold down "FUNCTION" buttom and key in, [C] [6] [D]. Then release "FUNCTION" button.3. To disable crossband 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 crossband function untill squelch closes andhandheld quits transmitting! ***Figure 1.--------------------------------------------------------------------l . .------------DIODE-Da--------. ll D915 +-+ ['] D909 : ll . .------------DIODE-Db--------+ ll D916 [ ] ['] D910 : ll . . : ll D917 +-+ +-+ D911 : ll .----------------------------------------. : ll l .-----------. l : ll l .' '; l : ll l .' '; l : ll l : BACK OF : l : ll l : SPEAKER : l +--+ +-:+ ll l '. .' l : : : ': l D907l l '. .' l +--+ +--+ ll l ------------- l ll l l +--+ +--+ ll l Removing this diode results in -----> l : --REMOVE-- : l D913l l expanded UHF coverage from l +--+ +--+ l'--------' 400 - 479 MHZ. l ll +--+ +--+ ll : : : : l D908l +--+ +--+ llllll +--+ +--+ lRemoving this diode results in -----> l : --REMOVE-- : l D912enabling the unit as a cross- l +--+ +--+ lband repeater. l ll +--+ +--+ ll : --DIODE--- : l D???l +--+ +--+ lll------------------'FIGURE 2