Modifications for the ICOM - RogerK

19-07-1998(IC-02) Another band expansion mods for Icom IC-02The following method of modifying the Icom IC02 is an alternate to the IC02.MOD file. This one should give you PL out of bandwithout jumpering 5 VDC to the tone chip. Use 1N914 or equivelent when adding diodes.1. On the logic matrix, remove D402 and D403.2. Add D402, D403 and D404 with the cathode at 4 o'clock and the anode at 12 o'clock.3. Retune the VCO to cover your desired frequency spread. My 02AT did not want to go beyond 163 MHz. I have a friendwhowas able to get his to the low 170s.4. To jump from 140 to 150 or from 150 to 160 (or vice versa) you must "tune across" the boundry, in the same way that youdo for an unmodified 02AT. For example, key in 149.995 and then move up until you are in the 150s. You can then enterany 150 MHz frequency (starting with the MHz).This modification is read 1387 times.top of page19-07-1998(IC-02) For increased receive audio and improved responseSolution: Remove C117. C117 is a .22 uf capacitor. It can be located by first finding the 8 pin IC that is neart the middle of the"Main Unit". Looking immediately above it (above pin 4) untill you see 2 round polarized capacitors. The one on the left is C117.It can be successfully removed by just bending it back and forth untill the leads break. Be carefull to get the right one!This modification is read 1051 times.top of page19-07-1998(IC-02) To increase the memory scan and search scan speedSolution: Install a 100k ohm resistor across R413. To locate R413 Remove the DTMF Board that is attatched to the inside front ofthe radio by removeing the two small screws. You will now have the logic unit exposed. IC401 (which is the postage stamp sizedIC near the middle of the board) is easily visible. Locate the bottom right corner of this device and continue down until you cometo the first micro chip resistor. This is R413. Carefully install a 1/8 Watt or smaller 100K ohm resist or across it.This dramatically increases the scan speed but also raises the "BEEP" tone frequency.This modification is read 1082 times.top of page19-07-1998(IC-02) ICOM HS-10SA VOX for IC-02AT ModsThe ICOM headset VOX model HS-10SA for the IC-O2AT can be a handy unit for mobile use but it has a serious limitation as itcomes from the box. There is no way to turn it off other than unplugging it! This means any conversation with a passenger,cough or sneeze goes out over the air.Fortunately there is any easy remedy. Remove the 3 screws holding on the rear cover and the single screw holding the circuitboard. Carefully lift out the board and locate R23. It is a 4.7K 1/8 W resistor located near the lower edge of the board.One end of it connects to the white lead of the cable to the HT. The other end connects to the collector of Q7. This is the keyingcircuit. In normal operation, Q7 is saturated when the VOX is active. Since the emitter of Q7 is grounded, R23 is effectivelyconnected from the white lead to ground, keying the HT. Carefully unsolder the end of R23 which goes to Q7 and lift this leadout.Drill a 1/4 inch hole in the center of the end of the case and mount a SPDT switch. The switch the author used was a C & K 7207which is a 3 position, center off, SPDT, with one side spring return momentary and the other side latching. This allows themomentary side to be used to key the HT manually, the latching side for the VOX operation, and the center OFF.Now connect the center pole of the switch to the end of R23 which used to go to Q7. Connect the latching side of the switch tothe hole in the board where R23 was (Q7) and the momentary side of the switch to ground (shield of cable to HT). Nowreassemble the unit and test.This modification is read 1015 times.top of page