KB2LJJ Radio Mods Database
Contents
1. 3 4 inch are two rows of diodes 14 diodes in the right column and 7 diodes in the left column For Icom 746 Radios with the diodes in the 1 2 6 7 9 11 and 14 positions remove numbers 6 and 7 leaving the other 5 in place Mod complete top of page Separating the Tx and Rx lines eparating the Tx and Rx lines on 2 meters in the IC746 could not be easier Put the rig on the bench with the front panel facing towards you and turn upside down with the front panel still facing towards you Remove the bottom cover At back left there is a 5 inch sguare metal screening plate held in place by four screws remove it You will see a miniature co ax plug and cocked labeled VRX Simply unplug tuck the original plug out of the way and plug in a new plug attached to a length of miniature coax which can neatly leave the rig through the hole on the back panel that contains an earth bolt Now you have your separate receive input You could cut off and re use the miniature co ax plug but I preferred to contact my local Icom dealer and buy a new one a couple of dollars the Icom description is PLUG TMP P01X A1 Min Coax IC 125 top of page Power mod for the IC 746 Remove bottom cover Find the voice module plug in Right behind it you will see 4 pots R993 144 mhz power adj R991 50 mhz power adj R989 HF bands power adj R990 AM power adj You can tweak these to up the power suggest on hf doing it on 40 meters you can get clo2. Author Rick Pemble pemble O ix netcom com This is a message from usenet alt ham radio There is the interface This one shows a 5 radio hookup just use the one jackif that is all you want The inductors are all RFI suppressors you can skip them if you want L1 L2 L3 L4 as well as C5 The important parts are the five 22uF electrolytic the Max232 IC and the 7805 regulator Easy to build works fine cheers Rick W4RP OM ICOM TRANSCEIVER i FR 22uF 16v 9S J1 Ct 22pF16V X 16 RSS nno RES ceva Ul H 24 LA 3 md 2 22 F16v H J2 ae 3 22yF16V J3 CI V 3 i C4 22yF 16 bi J4 RS 232C CI V 4 TO COMPUTER J5 CI V5 Tod J Knapp wrote in message gt I m looking to build a CI V unit for my ICOM 746 Although I m not really gt looking forward to giving ICOM 100 or more for a computer to radio gt feature I d sure enjoy th xperience building such a unit gt gt CI V allows your computer to communicate with your ICOM radio gt gt Does such a WORKABLE schematic exist Has anyone tried it gt gt Please advise gt gt Tod N9ZWY http www kb21jj com data icom ic 746 htm 5 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database IC 746 USA models All Band TX Modification Author Lyndel N7LT n7lt arrl net This information is to help clear the confusion about the ICOM IC 746 modification for out of amateur band transmissions There are a couple of different mods floating aroun
3. F band using RF probe should have very small sig on pin 1 and very large gt 6volts DC on the RF probe when applied to pin 5 When chip fails pin 5 goes to very near 0 millivolts on the RF probe C 746 MMIC IC 151 O IRF UNIT FAILURE ILLS ALL TX HF VHF uPD1678 icom number is 1110001890 lists about 10 bucks or less Changing this chip requires proficiency in surface mount desoldering and anti static protection measures vier Bill KOZL ICOM IC 746 Electronic Keyer Speed Modification http www kb21jj com data icom ic 746 htm 10 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database Hans Glista WAILWS hglista erols com Purpose The built in IC 746 electronic keyer speed is adjustable over the range of 6 to 60 wpm Most amateur radio operators never operate Morse code approaching 60 wpm I usually operate in the 15 to 25 wpm range and found that setting the keyer speed in this range is very touchy because the speed changes greatly with only a slight rotation of the Key Speed knob This modification limits the maximum keyer speed to about 32 wpm making the adjustment of the keyer speed easier Modification Solder a 1 5k ohm resistor across C8 of the S LOGIC Unit PCB If a maximum keyer speed other than 32 wpm is desired increase the resistor value for a higher maximum speed or lower it for a lower maximum speed Procedure 1 Remove the top cover 12 black screws and 2 chrome handle screws 2 Remove the bottom cove
4. KB2LJJ Radio Mods Database www r6 ru4montesecchieta it IZSCCV Modifications for the Icom IC 746 IC 746 out of range TX RX IC 746 Modification Extended RX TX for IC 746 Separating the Tx and Rx lines Power mod for the IC 746 Solutions for chip blowing with mPC IC 746 out of range TX RX n IC746DW JPG you can see the open bottom side from the transceiver and you will see a red marked area too This marked area you can see again and bigger in the picture IC746SMD JPG Now something about IC746SMD JPG There are some green frames This are diodes which must be on this place There are some red frames This are diodes which you have to remove Where no frame is there is no diode in my transceiver After removing the red marked diodes you should can RX 60 khz 60 MHz and 118 Mhz 176 MHz TX 100 khz 60 MHz and 118 Mhz 176 MHz http www kb21jj com data icom ic 746 htm 1 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database ENNAN KAT KAT YTY IYITIIKTKTAIN IC 746 Modification Remove the twelve screws holding on the bottom cover With the Radio laying flat on it s top remove the bottom cover Turn the radio so that the front panel is to your left and the antenna connectors are to your right Locate the IC labeled ICOM HD6433042SF About 3 4 of an inch to the right is a vertical row of diodes The left hand column of diodes has 7 diodes 14 possible spaces The right hand row is full with 14
5. d 2 and for PSK31 very weak signals Some week ago I found in a Ham fair an FL100 CW filter for the IC746 at a bargain price and in the last days it happened to me to have some time to devote to our hobby and so I installed the 9 Mhz IF filter for 500Hz FL100 on the IC746 for pactor 1 and 2 and psk31 as I am used to I followed the instruction on page 78 of the ICOM user manual After returning all the covers on I went to page 60 of the instruction manual to select the installed filter for the 9MHz 1 position I selected the FL100 Then I went on page 42 for filter program mode setting as suggested on the page 60 Note on the top of page 42 at the beginning of the chapter 5 11 1st paragraph Optional filters omissis Filters can be independently selected for each operating mode And so I went to program mode setting and pushed the filter button for 2 seconds and then chosed to program the CW and the SSB Narrow for 9M on 500Hz and 455k for 2 4 k but surprise the FL100 was not available on SSB I suspiciously read carefully the manual and find nothing on selecting filters depending from mode chosen or relation between filter type and or bandpass sensing nothing So I went to the usual dirty trick way to gamble with the filter program mode setting I told the IC746 that the installed filter was an SSB Narrow 1 9kHz one the FL223 type All OK hi Dit ssc Then I went again on the procedure of page 42 and
6. d for the IC 746 For USA models the following information is the ONLY mod for the IC 746 I verified this with my contacts at ICOM They verified that this was the ONLY modification for the IC 746 USA model and that there were NO others I then performed the modification and the radio transmits from about 100KHZ to 60MHZ and 118MHZ to 176MMZ so be careful with this mod Read the following instructions all the way through before performing this mod Perform this modification ONLY if you feel capable of soldering VERY small surface mount diodes Do this totally at your own risk Turn the radio upside down and position the front panel to your right The main tuning knob will be to your lower right and the microphone connector to your upper right This will orientate the radio in the proper direction to read the parts layout identification silk screening Note the IC part numbers will be UPSIDE DOWN Remove the twelve screws from the sides and bottom securing the bottom cover Locate the Circuit board with the Optional IF filters The filters will be in the upper left hand corner of the circuit board Look to the lower middle of the circuit board for silk screening that reads Option UT 102 almost the center of the radio Immediately to the right of the Option UT 102 silk screening you will see two columns 14 positions in each column of VERY small surface mount diodes in a tight configuration I ll call them diode positions 1 14 This colu
7. diodes Remove the diode in the 6th space from the top in the left hand column DO NOT remove anything from the right hand column This should get you TX from about 100KHZ to 60MHZ and 118MHZ to 176MMZ Do this totally at your own risk Never ever transmit out of the ham bands or your privileges John Schmitz NS8E Additional information After having put a forward reading watt meter on my 746 i have found that there is NO loss of power due to this mod It is still putting out the full 100 watts when you have a good match 5 100 on SSB and FM and 2 40 on AM I have also discovered that the TX was NOT opened up above 54MHz to 60MHz the top end of the 6 meter band switch on the 746 The only effect i have noticed is that sometimes while using the built in antenna tuner in manual tune the LCD display sometimes blinks or lights up with all functions showing or sometimes disappears below the line Also the band edge beep function option no longer works because with wide open TX there are no more band edges One must be careful to stay within their operator band privileges These are the only adverse effects i have noticed with Mr http www kb2ljj com data icom ic 746 htm 2 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database Schmitz mod top of page Extended RX TX for IC 746 Open the bottom cover of the IC 746 Place radio on surface upside down with front to your left Find chip label HD6433042SFB24 To the right of this chip
8. his helps IC 746 modulation on AM Author vs420mike66 O aol com If you want more crisper and louder modulation on AM turn radio upside down and remove cover at the top right hand corner of radio you will see a variable that says AM mod Clockwise increases mod and counter clockwise decreases mod You might want to use another radio on the same frequency so you can hear results The radio that you are listening with needs no ant screwed in to it being that you are only listening I have done this and mine has loud crisp modulation Remember no compression on AM you will find that it will muffle you on AM Do at your own risk 738 http www kb21jj com data icom ic 746 htm 7 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database IC 746 Backlight Author vs420mike66 O aol com Here you go guys here is the repair mod for the backlight Remove top and bottom cover Remove the 4 screws holing on the face 2 on left and 2 on right of face holding it to chassis There s 1 ribbon cable connecting the face to main unit just pull strait out Remove knobs just by pulling them off VFO just pulls off also Unplug all ribbon cables on back of face number them with a permanent marker if you think you might mix them up There is 5 screws holding the top circuit board in take them out and lift up board be careful and feed 2 of the ribbon cables through the board On the back side of this board there are 2 steel boxes
9. mn should have diodes in EVERY position 1 14 The next column to the right is diode positions 15 28 This column should have diodes in positions 15 18 20 22 23 27 and 28 as shown below lt Remove this diode only Diode 23 is VERY small and has a small Y on top of it Use the finest pair of tweezers you have to remove diode 23 ONLY Make sure you remove diode 23 only and NO other diodes Make sure you have NO solder bridges as the diode pads are VERY small Use a clear piece of tape and tape the diode to one of the metal covered cans near the columns in the same orientation you removed it This way you ll have your diode to reinstall if you ever feel you need to and you ll know the orientation of the diode http www kb21jj com data icom ic 746 htm 6 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database This completes the TX modification Replace the cover and screws TX should be from about 100KHZ to 60MHZ and 118MHZ to 176MMZ Do this totally at your own risk Never transmit out of the ham bands or your privileges 73 Lyndel N7LT 01 15 02 03 04 18 05 06 20 07 08 22 09 23 lt Remove this diode only 10 11 X 12 X 13 27 14 28 the above was taken from the American post the diodes marked with an X are found in the European models and should be removed too i rang Icom U K and also had it verified by a friend who did the mod hope t
10. on the board Take the top off of the biggest one You will see a small square transistor with the B1201 on it This is the problem transistor that s been giving backlight problems This transistor has no way of cooling laying flat on the board remove this at your own risk You have to have a small tip iron and a good set of eyes and steady hands The center leg on the transistor is cut off this is the ground leg and the top of the trans is soldered to the board Heat the top of the transistor and lift it and it will come loose then unsolder the legs and lift Remember which way it came out Take the new trans and don t cut the center leg off the center leg needs to be soldered where the top of the transistor was soldered And the other 2 where they were from the start leaving the part standing up instead of laying flat on the board Now push the transistors side against the metal box and put some heat sink compound around the transistor and between the part and box now it can keep cool Thats it put the top back on and put the unit back together Replacement part s are NTE2525 or 2SA1244 or 2SB1201 good luck and take your time Works well http www kb21jj com data icom ic 746 htm 8 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database IC746 Using 500Hz filters on SSB for Dig Modes Author I2JJR Augusto i2jjr hotmail Hi there I ran usually my old TS440S AT with 500Hz IF filters on USB mode for the Pactor lev 1 an
11. r 6 black screws Remove the front panel assembly 4 flathead screws disconnect ribbon cable W18 that connects the S LOGIC Unit PCB on the front panel assembly to the MAIN Unit PCB on the chassis by pulling it out of its socket J1334 on the MAIN Unit PCB Solder a 1 5k ohm resistor across C8 of the S LOGIC Unit PCB C8 is located next to pin 1 of J601 See photograph for location red arrow I used a size 0603 surface mount resistor A leaded resistor may alternatively be used Reassemble in reverse order of disassembly ICOM IC 746 Electronic Keyer Speed Modification http www kb2ljj com data icom ic 746 htm 11 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database
12. rt from this test and related trick to get the 500Hz band pass for USB digital RX I would not suggest as necessary to buy and install such filters on the IC746 with the PtcII controller you may work very well on PACTOR psk31 rtty and other 500Hz band pass modes on the IC746 do not use the DSP and or NB NR sometimes good some others no The same applies for the SoundBlaster software programs like Digipan or others the normal band pass is more than adeguate and you may taylor it using the twin band pass tuning I recommend the narrow filters on TS440sat and alike more I suggest on them to replace also the 455kHz filters with other http www kb21jj com data icom ic 746 htm 9 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database that have better performances IN RAD has some good ones and the old good TS440S will copy nicely and happily very low level digital signals I hope this notes will be useful for some reader I will appreciate any feedback on this matter Thanks and 73 de I2JJR Augusto IC 746 Loss of tx power all bands Author Bill KOZL bbtech1 comcast net DC to LIGHT op amp uPD1678 actually a MMIC located on the RF unit bottom side of radio rear left remove shield cover will shut down ALL tx on ALL bands when it fails I have replaced three of them so far MMIC is the 11678 actually a uPD1678 Input is pin 1 lower right and output is pin 5 upper left pin on the SMD chip Check in FM mode any H
13. se to180 watts on 40 75 meters about 125 to 150 on 20 10 The pots are very small be careful not to use something to big the are all metal pots http www kb21jj com data icom ic 746 htm 3 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database Change resistor R157 from 10 Ohm to 47 Ohm close to this chip c2 03 18 265 RI 390 0 1 r ae E SN 5 un N gt Monitor Audio Output Too Low Author heloxx hotmail com The monitor function on the IC 746 tends to have low output compared to receiver AF volume therefore in order to listen to yourself you have to increase the volume When the PTT is released back to receive mode the AF setting nearly blows your speaker or your headphones If the monitor audio output is too low on your ICOM 746 you can add 4 7K resistor in parallel with R1087 This brings up the gain of IC1082 to a more reasonable level that can still be controlled by the monitor level function but with plenty more gain Technical Notes http www kb21jj com data icom ic 746 htm 4 di 12 23 08 2009 22 42 45 KB2LJJ Radio Mods Database These SMDs are located in the Main Board You will probably need a service manual to locate these parts on the main board Adding modifications to these very small parts requires some skill and a good magnifier together with the appropriate tools A 1 8 Watt resistor will be suitable for this modification but still require some precision Schematic for ICOM CI V Option
14. set the SSB N filter mode for 9M 1 9 kHz hi and 455k at 2 4kHz It runs OK having now band pass of 500Hz on SSB N mode available for Pactor lev1 and lev 2 and PSK31 On the TS440SAT I had to correct for the IF filter frequency moving the IF band pass slightly clockwise to fit it for the selected tone pair 1200 1400 Hz or 1400 1600 Hz and the same had to be done on the IC746 selecting as usual USB I had to tune the outer larger one of the twin band pass tuning about 90 degrees clockwise This proved to be quite a god setting for operation on USB Pactor level 1 and 2 using high tones I tested some lower tone pair compatible with the CW band pass but take care of the CW Pitch setting it should be tuned fully clockwise or you ll get no audio out and tested with 400 600Hz 500 700Hz and 600 800 Hz but although the PtcII controller I use is very versatile on this respect my ears are not and so being used to by ear search and pre tuning and then spectra fine tuning I endly went back to the usual 1500 Hz center freguency I got 1500 Hz as I am also using pactor level3 before it I was using 1300 Hz center Here people using other controllers like KAM or alike have to adjust their band pass tuning depending on the tones freguencies they use Actually I have not yet the FL52A 500Hz 455kHz filter if I ll find it at bargain price I ll buy it and test it I saw by now that having 2 4 kHz band pass on 455 kHz works I have to say that apa
Download Pdf Manuals
Related Search