Kenwood ts830s no drive on 20 meter band

Discussion in '"Boat Anchor" & Classic Equipment' started by M3UZB, Jul 10, 2018.

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  1. AF7XT

    AF7XT Ham Member QRZ Page

    M3UZB likes this.
  2. M3UZB

    M3UZB Ham Member QRZ Page

    Hi Dennis.

    Its begining to look like that this is the procedure I'm going to have to attempt. thank you for the pdf it will be very useful indeed.
    I will take my time with it, luckily for me I do have a lot of patience.

    Thanks again for you're input.
    Best wishes
    Simon.
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    I don't think the problem is your bandswitch . . .

    Something is causing your lack of standing current on 20m, which must be a faulty component.

    As I say, I need to study the circuit diagram when I get time, to figure what this could be .

    Roger G3YRO
     
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  4. M3UZB

    M3UZB Ham Member QRZ Page

    Hi Roger

    if it is a component I would rather wait and see what you come up with. I don't relish the idea of stripping the wafers if I can get away with it. I would rather replace a component. I seriously need to get some test equipment,I absolutely love this transceiver even though she's old and a little decrepit it makes me smile every time I turn it on the warm glow of the beautiful s meter and the slight creak of the tubes as they warm up anyway I'M digressing now.

    Thank you roger
     
  5. AC0OB

    AC0OB Subscriber QRZ Page

    Hi Simon,

    If you have done this already please disregard, but have you replaced the 12BY7A RF driver and cleaned it's socket above and below? I have had some very flaky situations in which the 12BY7A starts to lose gain with increased frequency as it gets gassy.

    I have also found that little dust bunnies at the socket can play havoc as well.


    Phil
     
  6. M3UZB

    M3UZB Ham Member QRZ Page

    Hi Phil

    I have taken the 12by7 out and inspected it by eye on physical appearance it looks new although the sheild is missing that encases it. I have yet to inspect the socket from the underside of the RF board.the socket from above looks clean.

    Tomorrow I will look at the state of the connections to the valve socket solder joints.
    Thank you Phil

    Best wishes
    Simon.
     
  7. G3YRO

    G3YRO Ham Member QRZ Page

    Unlikely to be that . . . if it works on every band except 20m, it's something else.

    Roger G3YRO
     
  8. AC0OB

    AC0OB Subscriber QRZ Page

    What I recommend is you download the service manual and see if you can identify those components that appear to have been replaced.

    We cannot rule out a bungled repair or modification.


    Phil
     
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  9. WR2E

    WR2E Ham Member QRZ Page

    Roger is on to something. Kudos.

    It sounds as if there is cutoff bias still on the tubes only on 20 mtrs for some reason.

    I can't get to my documents, all in storage at this time.

    My first step would be to measure the bias at the tube grids.
     
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  10. G3YRO

    G3YRO Ham Member QRZ Page

    Looking at the circuit diagram, all I can figure is that SOMETHING is preventing the rig going into Transmit mode on 20m.

    So some of the relays will NOT be going over when you press Transmit. (this is why you are not getting any standing current . . . and obviously why you are getting no output)

    As I say, I'm not very familiar with this rig . . . but although it has a VFO, this is part of a PLL system. Normally, if ever the PLL is "Unlocked" (or almost unlocked), most transmitters PREVENT the rig going to Transmit.

    So I'm guessing that the PLL isn't properly locked on 20m . . . and that's why you can't Transmit. (it's obviously working to some extent, or else you wouldn't be Receiving on 20m)

    Therefore I imagine the problem is in the alignment of the PLL / VCO circuits on 20m.

    Hopefully, the Kenwood Guru - Clif KA5IPF - will see this and post his thoughts.

    Roger G3YRO
     
    Last edited: Jul 12, 2018 at 2:04 PM

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