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Kenwood TS-440S transmit problem

Discussion in 'Radio Circuits, Repair & Performance' started by KJ7CDF, Jul 11, 2019.

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  1. KJ7CDF

    KJ7CDF Ham Member QRZ Page

    Hello, I have had a Kenwood TS-440 for a little while now and it has had problems for some time. When I first got it, It worked just fine with my current setup. I recently acquired an SWR meter and I attempted to diagnose the problem. So far, here is what I found:

    -No Transmit forward power

    -ALC meter is reading zero (Microphone is working)

    -Occasionally puts out up to 20 watts but then goes back to zero (It is quite unreliable in this way)

    -If I increase my voice volume then the effect on forward power is minimal (If anything, I would say up to 1 watt difference)
    - I have tested this to be true on all modes

    -receives fine

    -Mic is working just fine

    I suspect this could have something to do with how the radio is processing the audio but, I do not know. I have tried turning up the mic gain and it still has no effect.

    -Alan, KJ7CDF
  2. KO6WB

    KO6WB Premium Subscriber QRZ Page

    Do you get full power when in the CW mode?
    Have you checked the power supply?

    Just some suggestions.
    Also, you need to try operating into a dummy load and see if that makes any difference.
    If you are getting full power on CW then it's most likely a microphone problem. Try a different and known good working microphone.

    Hope this helps
  3. KJ7CDF

    KJ7CDF Ham Member QRZ Page

    PS is working

    No Power on CW either

    Thank you for the suggestion on the dummy load. I do not own one but, am considering making one for testing.


    -KJ7CDF, Alan
  4. KM4YTW

    KM4YTW Ham Member QRZ Page

    Have you opened it up? I had a ts690sat and a cap started leaking and corroded the tx trace on the board. Kenwoods are known for leaky caps and they will mess up circuitboard trace quickly. Not sure of your skills but a look at the boards would be a good thing. Look for black thru holes and spots on the boards
  5. KA5IPF

    KA5IPF Ham Member QRZ Page

    Have you read and understood the owners manual? If not start there.
  6. KJ7CDF

    KJ7CDF Ham Member QRZ Page

    I have looked at the circuit board, unfortunately, no evidence of malfunction there as far as i can see (I do not have much skill in this type of work but, I will continue to search the boards for leaky capacitors).

    As for the owners manual, I have looked at it but, there does not seem to be anything that would explain the radios behavior. I will read through the whole manual again and see if anything seems familiar.

    One thing to add: The manual was not very clear on the operation of the internal antenna tuner so, I did accidentally end up operating it with no tuner a couple times. I suppose that may have had something to do with the issue as I have read it can mess up the final amplifiers.
  7. KA5IPF

    KA5IPF Ham Member QRZ Page

    Don't look for fixes in the manual, look for how to set it up for different modes and how to use the tuner. It's all in there.
    KS4W likes this.
  8. WA8NVW

    WA8NVW Ham Member QRZ Page

    If you have tried to operated the TS-440SAT transmitter at full power with a high SWR, it is easy to burn the relay contacts on the PA output filter board. If you don't remedy that issue promptly, you will soon fry the PA output transistors, which is a very costly repair.

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