Modifications for the ICOM - RogerK

Delete cap. CT14 at pin 6 of IC3 on I.F. Unit.Rearrange the R9V to TR Q22 on I.F. Unit so that it is connected to unswitched "9volts supply.Do a similar mod. To the "9 volt supply to the A.F. unit to overcome surge pulse.Good luck de " RON " GM3SAEBy PA3AXOConnections to acc. Jack on the back of the tansceiver:Pin 3 Keyline (note that 200 mA current capability is required so a dil relay may give problems)Pin 4 af to convertorPin 9 FSK input TTL levelPin 8 groundOn main board:Remove C40/42/43/54 and replace by 0.1 uFReplace C69 by 10 nFOn RF board:Remove C169 and 127 and replace C165 by 0.68 uF when desired the relay to control an external linear amp can bedisconnected to reduce the clicking noisesGood luck and best 73 de Jack PA3AXOThis modification is read 961 times.top of page19-07-1998(IC-725) ICOM IC-725 MARS modificationsDISCLAIMER:This modification allows the radio to transmit outside of the designated Amateur freq. Transmitting where you are not licensed todo so is unlawful!Disassemble radio following instructions on page 24 of Instruction manual, steps 1 - 7, or as follows:NOTE:All instructions with the radio's front panel facing you unless otherwise specified!1. Remove all black screws from top & bottom covers and remove both covers.2. Remove the 2 flat head screws that hold the PA unit to the front unit. (top front of radio - Not the screws that are in theplastic front panel.)3. Remove the 2 screws that hold the PA unit to the rear panel.(Looking at the rear of the radio, 1 is above the ext. speaker jack & 1 is above to ACC(1) jack.)4. Unplug the 2 plugs from J11 & J12.5. D6. Disconnect the large black connector on the left side of radio.7. Slide up and out, the TUNER CONTROL SOCKET from it's holder in the rear panel.8. Remove the tape from the right side of the PA unit.9. Swing the PA unit up to the left and lay over flat.located to the left side, rear of the board, next to J4.You may have to remove J4 to allow access to D-5.10. Reassembly is As if you were opening a book! You now have the PLL unit exposed.11. Cut Diode D-5 from the PLL unit.D-5 is loca reverse of above.12. The radio will now transmit from 1.5 MHz to 33 Mhz. (It will transmit even lower but the power output drops off and I don'tknow if doing so will damage the transmitter.ENABLE PREAMP Bve bottom cover.1. Locate Q12 on Main Unit. 1/3 way from left side of board.Q12 is the transistor that bypasses the preamp below 1.5 MHz to avoid overload when listening to AM Broadcast Stations.2. Clip the lead of Q12 closest the front of the radio.That's it, the preamp will now work below 1.5 MHz! ENABLE NOISE BLANKER IN ALL MODES