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Scope usage

Discussion in 'Electronic Repair' started by [email protected], Apr 2, 2005.

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  1. Guest

    Hi folks;

    Again and again I see people posting here with various problems which
    would send me straight to the scope probe. Does anyone use these things
    anymore or what ? When you got immediate shutdown for example, what I
    do is scope the HOT. Does anyone else do this ?

    They'll disable shutdown, risk blowing the power supply or worse, check
    50 voltages and resistances or so, when all they needed was a scope.

    If you don't have a scope that'll get you to 200V/div, scope the line
    feeding the 200V recifier, or you can just crank the scope down to
    about 5V/div or so and just get the probe near the flyback.

    OK an old Mits RPTV comes in, the one with 2 SMPSes on a board mounted
    to the side (like a vs 4506 etc.)

    Clicks on, clicks off. I put the probe near the fly, nothing, I put it
    near each of the SMPS transformers and one of them is running a very
    short pulse width, pull it, leave it plugged in and quick check for
    shorts on the output lines, none, OK a few caps and an STR-S6301. Fires
    up.

    If I have a good waveform at the fly I go to the vertical, thumb on
    probe and adjust timing until I can see the 60 Hz. Outer yellow and
    green yoke lines, and bet it ain't there, or I could get a bad waveform
    at the fly and then it's time to disconnect the HV, and then the yokes.
    (in that order BTW). If I get a good waveform at the fly and vertical
    is working I go to the 130V line and set the scope to 50V/div. Center
    the trace on a line and watch it like a hawk as you hit the power. You
    can plainly see if it goes up three divisions, at that point it gets an
    SE130. If it levels off at what looks like 130 volts, I'll switch to
    20V/div and make sure. If it is indeed in regulation I go to the ABL
    line.

    After ALL that I MIGHT disable the shutdown if I have nowhere else to
    go. Why don't others do it like this. If you're familiar with that type
    of set, is there a better or faster way ? If so tell us. This is by no
    means the same for every set of course.

    The main thing is, I see scopes just collect dust in shops until I get
    there, sometimes. How many parts have been replaced needlessly ?

    Perhaps alot of techs need a scope class or something ?

    JURB
     
  2. I use a 'scope for almost everything, along with an audio generator and
    digital voltmeter. Of course I'm mainly an audio guy. I don't miss getting
    down on the floor servicing a console in the customers' house, or fighting
    with a new jug because the purity, convergence etc won't "quite" fall in.

    Mark Z.
     
  3. worldcitizen

    worldcitizen Guest

    Thanks for the detailed info. Much appreciated.
    By the way, I use my old Tektronix 547 with a dual trace 1A1 module all
    the time.
     
  4. Ray L. Volts

    Ray L. Volts Guest

    Mine collects dust just because it gets dusty so damn quick around here!
    Seriously, dust off everything and 2 days later new film of dust is present.
    Anyway, I use my Sencore SC61 on many repairs, not only for alignment
    procedures, but, as you suggest, to prevent unnecessary part replacement
    (easter egg hunting), which ultimately also saves time.
    Agree with that. Lots of techs who do use scopes don't use them in such a
    way as to get the most out of their measurements.
     
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