Repair Kenwood TS-820s

Discussion in 'General Technical Questions and Answers' started by KD0KLH, Mar 8, 2010.

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  1. KD0KLH

    KD0KLH Ham Member

    :) For starters I goofed, I bought 2 TS-820s off of ebay,
    just got my Tech Lic and made up a dummy Load for testing.
    Both of them will not TX,I replaced both 100mfd/500dcv capacitors,
    RF driver tube on one of the rigs.I have a service manual & very limited knowledge.

    Using the dummy Load my DVM reads 0dcv.

    Q:In the transmitter section,there is a schematic from the mic to
    the ant. Would it make sense to start checking voltages via the
    chart? I'm thinking of going right to the finals and checking the plate
    voltage 920 (750) and working back towards the mic.
    Another Question: (750) means ?

    I have tested the power transformer,it's fine.

    Maybe I'm asking too many dumb questions!:D Thanks
  2. WB2WIK

    WB2WIK Premium Subscriber

    Two rules:

    1. Never buy a rig you can't try out personally.

    2. The number in parentheses (750) means the "key down" voltage on transmit, as opposed to the "first" number, which means the "standby" voltage (not key-down).

    The TS-820S is a very easy rig to work on.

    I know it inside-out.

    But I'd never buy one without trying it out first. It was designed 35 years ago.
  3. K7SGJ

    K7SGJ Ham Member

    If, by your own admission, you are not familiar with trouble shooting, I would advise you stay away from the tube section. In fact, I would recommend you find someone who can elmer you in SAFE troubleshooting techniques. It takes a long time to become adept at successfully working on electronic equipment. Please, safety first!
  4. KD0KLH

    KD0KLH Ham Member

    If I decide to farm it out for repairs,one has SSB filter & CW filter
    Can I swap them over to the other rig? The one I want to have repaired
    does not have them.
  5. WB2WIK

    WB2WIK Premium Subscriber

    I don't understand the question.

    The rig won't work without the SSB filter...
  6. KD0KLH

    KD0KLH Ham Member

    I wanted to swap the IF board,got the answer "yes" from another ham.
    I have 2 TS-820s and wanted to keep the best looking one.
  7. AF6LJ

    AF6LJ Ham Member

    Chalk it up to a learning experience.
    We all started somewhere. :)
    The important thing is you were attempting to do something you haven't done before and what you learn in the process is valuable.

    New experiences are always a good thing.
  8. KD0KLH

    KD0KLH Ham Member

  9. WB2WIK

    WB2WIK Premium Subscriber

  10. KD0KLH

    KD0KLH Ham Member

    RF isn't DC. DVMs don't work at HF. What are you using to measure the voltage?[/QUOTE]

    My DVM :confused: taken at post of my home made dummy load
    Last edited: Mar 9, 2010
  11. WB2WIK

    WB2WIK Premium Subscriber

    My DVM :confused: taken at post of my home made dummy load

    If you're using a DVM to measure RF voltage, that's a misapplication of the DVM.

    RF is AC, and DVMs are not good into the radio frequency spectrum.

    If you want to measure RF voltage, you need an RF voltmeter.
  12. KD0KLH

    KD0KLH Ham Member

    :D But this is not AC The Dummy load has a built in diode detector.
  13. AF6LJ

    AF6LJ Ham Member

    Just a couple of things.
    when a diode rectifies an ac sine wave you get a DC value that closly resembles the average not the RMS value.
    The diodes by themselves won't give you an accurate reading without a compensation network to adjust for the effects of high frequency RF.
    (trying to keep it simple)

    Even the AC part of your DVM is not so simple. There are circuits that convert the output of the diode ( often an active circuit that uses an op amp not a diode by itself) to a voltage that correlates to the RMS value of the AC voltage.
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