Icom 706MkIIG

Everything for ’706 Lovers in One Place.

© 2003-2015 by Harold Melton, KV5R. All Rights Reserved. Rev.04/26/15

Shop for Icom radios here.

2015 Update

I finally located a used main board (the one with the IF filters, processor, etc.) and repaired my 706MkIIG, which failed several years ago. Now it works like new! The used board was $250, but I figured, hey, without it the radio is worthless, but with it, it’s worth about $900 (incl. sep. kit and FL-232), so why not just fix it and get back on HF? And maybe later, sell it (and some other stuff) and get a 7100 or something…

Introduction

Ah, the li’l 706: What can I say? I like it! It performs like big radio, but it’s small. It sounds good, and it’s well made. You can add the remote kit and put the control head and the radio body where ever you want them. They are reasonably easy to expand, calibrate, and connect to a computer.

This series of articles is a handy compilation of most of the mods and stuff I have developed or found on the web for the 706MkIIG, plus a chronicle of the little accessory kits that I have built to enhance my enjoyment of the 706.

2011 Notice: These pages have been divided into several pages for easier searching and linking to specific topics. Feel free to link to any and all pages. All KV5R articles are copyrighted and may NOT be reproduced in any other web site, but may be printed for personal and non-profit use, such as Ham clubs and classrooms, provided that links and attributions remain intact. These articles contains several schematics and kits designed by others. They are fully attributed and I make no claims upon them.

Disclaimer: The author assumes absolutely no responsibility, under any circumstances, for what the reader may do with this information. Building and connecting circuits, and performing adjustments or modifications, may damage your radio, void your warranty, and/or cause it to operate in violation of FCC rules and Type Acceptance, etc, unless you are very careful.

706

Continued…

42 thoughts on “Icom 706MkIIG
  1. icom706mkiig Keyer Paddles: continuous tone instead of dashes?

    Has anyone else got this symptom with the icom 706mkiig and an electronic keyer paddle: the internal generator generates dots for the left paddle but a continuous tone for the right paddle (instead of dashes).

    I can’t imagine that it’s the paddle or cable … could it be a setting in the 706mkiig? Or is it a defect?

    Thanks for any hints!
    73
    Greg

    • Go into the Setup menu and find the cw keyer settings; your’s is set to “bug” — it can be set to straight, bug, or paddle (iambic) mode. I forget exactly what the settings are called but you’ll find it in there.
      73, –kv5r

      • That did the trick, thank you very much! (In quick setting Q4 CW Paddle I now set “n” for normal mode) I somehow misunderstood the manual …
        72, Greg HB9GNA

  2. When You did replace the mainboard, where did You put the old non-functioning board?
    I am desperate of getting one adjustable coil form mainboard (L512 on schematic S.Coil LS522).
    None of the Icoms offices are able to get it to me as this part has been taken out from parts catalogue.
    So maybe we can do a deal with You?

  3. NO AUDEO COMING OUT

    the squelch is counter clock wise and volume is up
    still receive signal on all bands (signal), Mic is unkey
    Transmit is good on all bands I can get into on club’s repeater 2.2 miles
    …good AUDEO
    On 10 and 6 meters i put on FM mode to monitor on my
    scanner as Receiver so i put 706 on dummy load to transmit on
    all bands.
    for 2m & 440 on simplex…good modulation.
    Went on TROUBLESHOOTING chart, Page 57,
    That i did, so I took cover their a 4
    Amp fuses inside check w/ DVM…good fuse
    Put cover back on. I hookup CABLE with rj45
    one and pin 3 audio and ground to Amplified
    speaker, Nothing. I hookup the amplified speaker
    To data jack to check audio coming out by using ext. amplifier
    And I Have audio coming out “sweet”.
    The audio amp in the radio is not.
    Ptt not working,rj45 back and
    audio from Mic not working,rj45
    under control head

  4. Hello! I have a used 706MKII (not G) that has no CW output but does key and have sidetone. SSB and AM work fine, as does receive. Red front TX light does not come on. I have service manual and some troubleshooting knowledge. Could you possibly point me in the right direction? Rig is from estate sale, dont know history but appears unaltered inside.

    Thank You

    Tom Mydosh WA2FWE

    • It won’t transmit cw unless you turn on Break-In (semi or full). BkIn is on one of the F buttons when in cw mode.

  5. My 706MKIIG has developed an issue. Receive is fine. Transmit audio is horribly modulated, all modes (tried FM, AM, SSB). Both VHF/UHF and HF. Tried 2 mics. Hum/Buzz. RF develops full power on all freqs. Can hear modulation via the mic, just not at all clean.

    Before this, the radio had stopped transmitting at all on 2m/70cm but seemed fine on HF. After reading to do a hard reset, I did so and the transmit came back OK, but now the audio was badly modulated – both in HF and VHF/UHF.

    Adding a PL tone won’t bring up a repeater.

    FWIW, about a year+ ago, I recall smelling a burning component smell during XMIT of the 706. I wasn’t sure it was the 706, but stopped transmitting nonetheless. I believe I was on VHF. Rig seemed to operate OK afterwards.

    Opened it up today, examined all the boards. No telltale burned component(s) I could locate. Finals & pre-driver looked OK. Didn’t check bottom of finals / driver board. Filter / relay board looked good, as did CPU board. Radio functions as it should, develops full power on all frequencies. Receive is great. But useless on XMIT all frequencies. Seems like it’s in the audio section. Thoughts?

    Thanks,

    N0TM

    • Tonight, I will check the VCO voltage. I’ve not checked for frequency alignment and I’ve a suspicion it’s off a good bit.

      N0TM

      • Great news. I didn’t get around to checking VCO, but almost sure that’s the issue. I determined that AM and SSB are OK. It’s FM that’s off frequency anywhere from -15 to +15 KHz. So of course it won’t bring up repeaters and sounds like badly modulated audio. Phew. Went from a condition that looked like blown VHF/UHF finals to the twist of a little trimmer in the span of a day. – N0TM

        • And the bad modulated audio on SSB and AM – I do think the rig needs tweaking in that respect. I need some better test equipment (or take the rig to a friend’s). But I did determine the DTMF Icom mic has really low and somewhat muddier response compared to the stock HM103 dynamic mic. I haven’t XMIT’ed much with the rig since I picked it up – and I don’t think anyone had the heart to tell me my audio was so bad. We need to be honest about these things! 🙂

          N0TM

        • My 706 is transmitting 10KHz low when operating FM but the audio sounds fine. What trimmer did you adjust to fix this. I have just started trouble shooting and this could save me much time. I am on HF most of the time but every once in a while I need VHF.

          John WD5IKX

          • See comment #2 here:

            http://forums.qrz.com/index.php?threads/ic-706mkiig-fm-problem.64459/

            “There is a variable capacitor C1022 which needs to be adjusted until the voltage across the varactor is in a normal range. This sets the free run freq. of the PLL oscillator. The voltage at test point CP 1011 needs to be at 1.8 volts at full power transmit in FM mode on 10 meters.”

            There’s a link for the Service Manual there too!

            This issue prompted me to get a decent dummy load (MFJ 300w dry for about $50). The manual wants you to adjust while at max power on 29.6MHz (or thereabouts) in FM. I had to adjust the trimmer I think about 1/4 turn to the left.

    • The 706 has only 1 crystal oscillator (60 MHz) and everything is derived from that by the processor. See my 706 Calibration page.
      If it’s off 10kHz on 2 meters, the master osc is WAAAY off, and you need to get that calibrated before messing with the vco or anything else.
      73, –kv5r

      • Turns out it was just FM, which is what led me to the VCO. Sure enough, following the Service Manual, I adjusted the trimmer about 1/4 turn, which brought the voltage at the appropriate test pad from mere mVs to 1.8v. Voila, FM was back.

        So it seems the rig is 100% now. That said, given the age, I’ve set the power across the board to 5, in the interest of preserving the (original design) finals.

    • Hi Fred
      common fault with the 706 not switching on is the head connector which locates when you mount the head on the radio body. Give both halves a squirt of cleaner and rub with a cotton bud. Should turn on after that.

      Hope this helps
      73s Joe

  6. Hi , I need a PLL board for my icom 706mkg11 tranceiver in order to get the unit working again. Can someone help me. Thanks K2ZIN

  7. Hi,
    My name is Ricky – KM4VAZ and I am located in Kannapolis, NC. One of my hamster friends has an Icom 706 MKII-G which he has owned and operated for years without any flaws. He had it mounted in his vehicle on his dash. Recently it started to lock up after getting warm and he would have to unplug it and plug it back in then it would work fine again for a while then it would lock up again. When I say lock up, I mean the display would freeze, no response from any buttons or switches, could not key up due to no response from the mic, no reception on the speaker. It would just freeze until he removed power and reapplied power then it would work for a little while then do it all over again. Would this be caused by the common fault of the H/V line due to a chemical reaction from the rubber support boots on the bottom of the boards or would this be a sign of an overheating CPU requiring new heatsink compound on the CPU? I work on electronics daily but this one has me stumped. Could you point me in the right direction or explain what may be happening?

    Thank you in advance and God Bless.
    73’s, KM4VAZ

      • The cpu is an 80-pin smt on the bottom of the main board, no heatsink.
        That one will likely need a new main-board, they’re occnly used on ebay for ~$250.

        • Thank you, I will try that. Also, I did check for the open circuit on the H/V line under a rubber boot on the PLL board like most people mention and it is open and the rubber feet on the bottom of that board is hard as a rock. I will take care of that open circuit then reseat every ribbon cable. Hopefully, thats all it is. He says he kept it in his vehicle for years on the dash, I told him that is a no no.

  8. Hi. I need help about Idling current adjustment. I have the service manual of the IC706MK2G but it is not so clear for me. I have some doubts about procedures. I measured 1.5 A idling current at tx with Q2 MIC Gain adjusted to 1 minimum at the beggining of the (step 1). I need to increase this current (0.5 A R162 according to the manual) so, at the end of the (step 1) I have an increased of current of 2.0 A. Is this correct?. Can anyone help me ?

  9. I am using my old ic706mkiig in my emergency go box. I have a Timewave TNC and am running it to my MacBook Pro.

    For packet I use a simple terminal program and it works just fine, it is plugged into the radio’s mini-DIN plug on the back, this has been working just fine.

    Now my dilemma, I have another interface that I want to use with Fldigi because the local ARES uses it with EMBEMS. The interface I have uses the VOX to trigger and to date, I cannot get it to trigger, and I am using a usb/serial adapter and no Civ. I do have it, but never thought about bah

    • If you mean your soundcard interface uses the radio’s vox, it won’t work on the 13-pin aux input, as the 706 audio input on aux jack bypasses the vox circuit and you must use the mic jack as input to use the radio’s vox.

      If your interface has its own vox circuit, it should work; an external vox should ptt via the aux jack.

      Either way, all you need is audio lines; you don’t need a serial port unless you want hardware ptt and/or civ.

      Note that fldigi is the one program that will not civ and ptt on the same port. You could use hardware ptt via your usb-serial adapter, then use a usb-civ adapter for civ if desired. Import usb-civ adapter/cable gadgets are ~$25 on ebay etc; they present to the computer as a virtual serial port, different than the one presented by your usb-serial adapter, and thus will work with fldigi.

      Also check the “hsend-sel” in the setup menu; it determines whether the ptt pin in the aux jack works for hf, v/uhf, or both. I don’t know what it does with the 8-pin data jack’s ptt line. See the 706 User Manual.

      See also the interface page in this series. A couple schematics there might get you going.

      73, –kv5r

  10. Hello,

    Here’s a strange one. Listening to cw there is an intermittent dropping of the tone which sounds like you are listening to cw on am. This is kind of a raspy, hissing sound and not a pleasant cw note at all. Can’t really predict when this will happen but usually in the middle of a cw qso and then it will go back to normal just as un predictably. Other modes seem to be okay. Transmit is good.

    Any hunches, theories or guesses are appreciated. Are parts available for a radio this old. Is this repairable?

    Thanks and 73,

    Ed, W8EO

    • I’m guessing you don’t have another CW op very close-by that’s overloading your receiver? Otherwise, might be a dirty relay contact on filter board; probably gonna need a tech to put it on the bench. I think most parts are still available, but fixing a serious problem is usually a matter of swapping out one of the boards, once the problem is located, since almost all the parts are SMT. They aren’t cheap, $100-$250 per board (used pulls via Ebay).
      73, –kv5r

  11. Dear friend, Need your help…my ic 706 mk2 is completely deaf on all bands and there is no tx power either. I hear the relays click while changing the bands. Best regards vu3npi

    • Only thing I can suggest is, make sure you don’t have a wide/narrow filter selected that isn’t installed. Otherwise, you’re gonna need a radio technician to put it on a bench and test it out. Also make sure they do a full “factory” alignment, per the service manual, after fixing.
      At least your filter relays are clicking! That, and ability to operate the display, means your 8V system, main processor, and master oscillator are working.

  12. Hello..My 706 doesn’t go to full power on some HF frequencies.With a dummy load attached,I get barley any power at all on the upper hf bands.I wired a Signal link USB unit to my radio&found that I hooked up the jumpers on the the signal link incorrectly.Think that might have damaged something.Help me out?Thanks

    • Sounds like a filter board problem. You should hear relays clicking when you change bands; those are the various output bandpass filters clicking in. If not, its trying to push RF thru the wrong filter, hence, very low output.
      But I can’t see how wiring a Signalink wrong would damage the filter switching circuitry, unless the ACC jack has a pin that signals bandswitching (for an amp) and you accidentally put 12v on it and blew something like a pin diode in the filter control circuitry.
      You’re probably gonna need a repair shop.
      73, –kv5r

  13. I need the front detachable panel for the icom 706 mkiig.
    My display on the panel all of a sudden got a burnout and the display is difficult to read.
    Kindly email me on callcyrus@gmail if any one wants to sell the front panel only
    cheers
    Thanks

  14. Anyone know where I can get one of those little knobs for this radio? One popped off in the car and I can’t find it. Thanks much

    • hi
      you can buy the little knobs from icom uk,
      buy the pair as they have a little red mark on them now,
      they are about £1.50 each.
      regards paul

  15. I have the icom 706mk2 and will be using it on 2 meters as my base at the qth. wondering if you could e-mail me a easy step by step of setting up this radio for 2 meters. off set, plls tones, split, memory, scan, ect. i got it to trans. and worked one of our local repeters with a good report. just wondering? tom, kf4csu

  16. Hi!
    I had a bad accident with my ICOM 70MK2G and both potentiometers from front panel need to be replaced! How to get them? On e-Bay I found other things! Pse help!

    • You need to either disassemble the front panel and get the part numbers off the pots, or from the 706mkiig service manual (free online), then contact an Icom service center. But Icom parts are expensive so first try to find OEM equivalents from mouser or some other big parts supplier.

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