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HV probes, & flyback measuring.

Discussion in 'Electronic Repair' started by Dani, Mar 31, 2007.

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  1. Dani

    Dani Guest

    What do you guys use for HV Probes? A stand alone unit, or a DMM ad on
    unit? Also, I'm looking at getting a Circuit-Test LCR meter Model #
    DLM-240, or something equivilent.Ranges are: Capacitance to 2000uF,
    Inductance to 200 H, Resistance to 20M Ohm

    Is this good enough to measure bad flyback windings? What do you guys
    use? Thanks, Dani.
  2. Wild Bill

    Wild Bill Guest

    There are lots of good HV probe styles available. I kinda like a probe with
    a built-in analog meter, just because it is simple to use, and doesn't
    require a separate meter, although I have and use the types that plug into a
    DMM too.

    See the FAQ section about flyback/IHVT testing. One important test is an
    inductor ringer, which can check for shorted turns.
    There are several tests/checks to be done to analyze the quality of
    flybacks. Some Sencore testers have a variable horizontal drive signal that
    can be used to drive the primary of the transformer (out-of-circuit), for a
    relative output test.

  3. Jerry G.

    Jerry G. Guest

    In our shop we prefer using a stand alone instrument for measuring the
    CRT high voltage.

    We are now finding that investing in to anything to do with servicing
    CRT equipment is becoming more limited and less feasable as time goes
    on. The cost of the flat panel TV sets and monitors are dropping
    every month. At the same time, manufactures are not interested in
    having the burden of having parts distributions for the CRT models.

    As for the LCD and plasma devices, these are mostly serviced at the
    modular level. For servicing, they usualy require dedicated tools and
    service information.
  4. James Sweet

    James Sweet Guest

    I use a Fluke HV probe that plugs into my multimeter. I think it's rated
  5. Jim Yanik

    Jim Yanik Guest

    More likely 50KV.
  6. James Sweet

    James Sweet Guest

    Just checked and it's 40KV, at any rate it goes higher than I've ever
    had to measure.
  7. Jim Yanik

    Jim Yanik Guest

    let's hope you don't encounter any CRT anodes at 40KV.....unless you're
    wearing your lead undershorts! ;-)
  8. James Sweet

    James Sweet Guest

    From the look of the thing I suspect it could safely go much higher.
    Not to say one should routinely abuse something, but Fluke is well known
    for using conservative ratings with lots of safety margin.
  9. Jim Yanik

    Jim Yanik Guest

    I was thinking of X-ray generation at voltages above ~25KV,not the safety
    of the probe.
  10. James Sweet

    James Sweet Guest

    I've come across TVs and monitors with 35KV anodes, mostly projection or
    very high resolution.

    I saw on a website once they were trying to generate xrays with a CRT,
    even up as high as 60KV or so there was not a measurable amount due to
    the leaded glass. A few rectifier tubes though did generate enough xrays
    to take a few pictures.
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