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Kenwood TS-940S

Discussion in 'General Technical Questions and Answers' started by GM0PHW, Feb 2, 2009.

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  1. GM0PHW

    GM0PHW Premium Subscriber QRZ Page

    Got a TS-940S and I am experiencing intermitant problems, sometimes when it is first switched on there are no lights or LED's but if you turn the tuning dial, it all lights up but not as it should, the lights, frequency and LED's, come on but are very eratic, i.e. frequency display does not read correctly and it sometime goes into transmit without the mic being keyed for a short period, then it appears to settle down and is normal again, had a few QSO's with excellent reports but wondered if anyone else has had similar experiences.

    Many Thanks,
  2. W9GB

    W9GB Ham Member QRZ Page

    This is a great radio, and was a long time DX contester favorite, but does requrie a bit of TLC.
    There are a handful of top Kenwood service technicians -- that will repair these for handicapped amateurs -- or those with no techncial/repair backgrounds.

    Jeff King ZL4AI / DU7 has assembled all of the service / repair notes for this fine radio.

    The Yahoo Group: Amateur Repairs --
    currently has a current discussion on TS-940 repairs.

    This radio has a large number of plug/connectors from the PC boards to the wiring harness. Over the years these connections can become intermittent.

    In addition, the TS-940 AVR board (voltage regulation for circuits within the radio) .. can become problematic (failed components, resistors opening, capacitors drying out). Remember that this radio (1980s vintage) is over 20 years now......

    Last edited: Feb 3, 2009
  3. G0GQK

    G0GQK Ham Member QRZ Page

    That helpful reply wasn't much use to someone living in Scotland ! I believe there is a TS 940 group on Yahoo, have a look on Google and you will probably find it. If you do need to have a repair or service job, I know its a long way from your home but Castle Electronics near Welshpool is a very fine radio engineer.

  4. W9GB

    W9GB Ham Member QRZ Page

    I would not insult a Scotsman with such a statement :D
    The answer applies to any TS-940 owner!
    Jeff King, ZL4AI is from the South Island of New Zealand ..

    TS-940 Group on Yahoo Groups -- 220 members

    Kenwood Communications UK, has the following network of Amateur Radio Repair Agents in the UK.

    Waters & Stanton
    22 Main Road Hockley
    SS5 4QS
    Tel: 01702 206835
    Fax: 01702 205843

    Castle Electronics
    Pool Road
    Llanfair Caereinion
    Welshpool, Powys
    SY21 0HN
    Tel no: 01938 810778

    Nevada Electronics
    Unit 1 Fitzherbert Spur
    PO6 1TT
    Tel: 02392 313090
    Fax: 02392 313091

    Martin Lynch & Sons
    Outline House
    Guildford Street
    KT16 9AS
    Tel: 0845 2300 599
    Fax: 01932 567 222

    Acoustic Services LTD
    66 Place Farm Way
    Monks Rosborough
    Princes Risborough
    HP27 9JY
    Tel no: 01844 347600
    Opening hours: Monday to Friday 9.00 to 6.30
    Last edited: Feb 3, 2009
  5. KX2E

    KX2E Ham Member QRZ Page

    I acquired a 940 abt 9 yrs ago with a similar problem. To my recollection, all I did was pull the multi pin connectors (very carefully) in the digital unit, very sparingly applied some caig cramolin blue or gold, and re-seated them. The unit has worked w/o trouble ever since. The previous owner was a smoker and that may have attributed to the problem but in my experience these type(s) of connectors and their plating become problematic. At least this is a simple procedure that at worst, if all goes well, will only take up a little time. Take your time and keep track of everything.
  6. GM0PHW

    GM0PHW Premium Subscriber QRZ Page


    Thanks for all your replies, I will try the fix that KX2E mentioned to see if this works Ok, if not I will try all the others. I will let you know how i get on.

    Any other advice is also welcome.

  7. 3A2MD

    3A2MD Ham Member QRZ Page

    TS 940 S cannot transmit SSB

    I just got a TS 940 S from my cousin SK , no problem in CW, but in SSB I cannot transmit, have you an idea WHY ?
    3A2MD Laura
    Last edited: Mar 8, 2009
  8. G0GQK

    G0GQK Ham Member QRZ Page


    Same suggestion for you, go to the Yahoo 940 group and they will be able to give you advice.

    Re my comment about being not helpful to someone in Scotland. Its no use giving people US information if they live 3,000 miles away !

  9. WB4KZI

    WB4KZI Premium Subscriber QRZ Page

    No Kenwood support for TS-940s anymore

    My 10 year old (I bought it new) Kenwood TS-940s went "south" this morning. It stopped transmitting in the middle of a DX contact and I knew by the familiar "smell" that something had cooked! Sure enough, when I removed the RF output board cover, I saw transistor Q2 was burned. I called Kenwood East and Kenwood West to try to see if I could send it to them to get it repaired. They both said that they did not support the radio anymore and didn't have parts for it and couldn't repair it. I could probably repair it myself if I can find the parts. I couldn't asked for a better radio but I think Kenwood's repair policy stinks! I will try to find a third party repair shop to repair it if I can't. I'd rather someone familiar with the radio repair it, and preferably a Kenwood repair center. But it "ain't gonna happen". I've always been a "Kenwood man" but will think twice about buying anything else from them and I suggest you do the same!:mad:
  10. W9GB

    W9GB Ham Member QRZ Page

    The radio is over 20 years old. You will not find many Detroit Big 3 auto manufacturers supplying adequate repair services for an automobile that old -- these days!
    Some of the parts used in this radio are no longer available from OEM mfg. (obsolescence)
    I would suggest a phone call to Clif Holland at Avvid [since you are in the USA].

    John at LPC Wireless is another option (I have not used his services)

    The Automatic Voltage Regulation (AVR) board is a KNOWN Problem with this radio.
    This is covered in the earlier links from Jeff King, ZL4AI
    When it fails -- it takes out these expensive RF power transistors.
    Section 2 of his extensive repair notes:
    Kenwood can not control their suppliers (and neither can Yaesu, Icom, Motorola, etc.).
    For example, the later TS-850 is another great radio --- BUT the Japanese mfg. of 2 highly integrated ICs is stopping production of that specific part!! It happens far more often than you are likely aware -- sometimes in the middle of a popular production run -- hence Rev B or Rev 2 comes out -- or the model stops after the factory parts inventory is exhausted!
    Your statement just shows a lack of knowledge -- that this has been the current operational
    constraints for the last 15 years. You stop vertical integration approaches (where you make all the parts) to save money (but raise your dependence and risk!) -- you are then dependent on these other OEM mfg. for your overall production of the system/unit.

    Kenwood has been quite GOOD at giving dealers, distributors and amateurs
    advance notice of these End of Life (EOL) / Service announcements -- whenever it can.

    Last edited: Jan 13, 2010
  11. VE7ZN

    VE7ZN Ham Member QRZ Page

    Do you still have the '940? Are you willing to sell it?
  12. KA8RAW

    KA8RAW Ham Member QRZ Page

    The TS-940s is a great radio, but because of its age, they are starting to develop problems. I had to repair mine, soon after I purchased it, and I recently repaired another one that had a couple of bad caps.
    I have also saw battery leakage in a few of them too, so if you are going to service it, battery replacement would be a good idea.

    KZI, it is possible that a bad cap or something caused the failure of Q2, so check the circuit before just replacing the bad transistor.

    Laura, does the radio have modulation in the other modes (AM/FM)?
    If not, try another microphone first.

    As KX2E has indicated, there are many issues with those darn molex connectors, and bad solder connections galore.

    I love the TS-940S so much, I wrote some nice computer interface software last year, it's totally free, you can find out about it here:
    Of course you will need to have the Piexx interface board, or Kenwood's interface board to use it.
    Last edited: Feb 7, 2010
  13. DJ7KH

    DJ7KH Ham Member QRZ Page

  14. KX0Z

    KX0Z Ham Member QRZ Page

    However there are people in the US that might see the information so it is usefull to them, hence not a wasted post..
  15. W4HLR

    W4HLR Ham Member QRZ Page

    TS 940s power supply

    I am needing a power supply for the 940s board number is x43-1500-00. The serial number on this rig is 9090159. If you can help please email me . Thanks in advance if ya can help. Howard
  16. N8YX

    N8YX Ham Member QRZ Page

    To the OP:

    The symptoms you describe are typical of a PLL Board failure.

    It is located underneath the Digital A board's bottom shield; top side of the radio.

    Remove the Digital A and PLL boards; you'll need to disconnect the headers from the latter but can swing the former away without having to remove anything. You will find a ~1"x1" piece of black foam stuck to the foil side of the PLL board. Carefully remove all traces of the foam and resolder all of the connections which were covered by it. Then mount the PLL board and plug all of its harness connectors back into their receptacles. Lastly, check to see if the synthesizer will now lock. Adjustments may be required, and since the synthesizer is a 5-loop design a 100MHz 'scope and the service manual procedures MUST be utilized.

    This "foam failure" is somewhat common and is well documented on various TS-940 sites. The foam (a VCO microphonic damper) becomes hygroscopic as it ages and will cause oxidation of the underlying solder connections...leading to circuit failures.
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