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No Trace Leader Oscilloscope

Discussion in 'Electronic Repair' started by Angelo Andriola, Sep 14, 2003.

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  1. I've got a Leader 1060 60Mhz analogue 'scope with no trace on the screen.
    The power LED comes on and the Illumination for the screen works. Any ideas
    on what could be the cause of this fault. It was working fine 4 days ago.
    Any help appreciated.
     
  2. Failure in any one of the circuits inclusive of the video and deflection
    amps to the power supplies anad hv circuits. Be advised, if you do not have
    experience diagnosing and repairing these types of test equiptment it may be
    best to have it serviced at a repair depot.
     
  3. Tweetldee

    Tweetldee Guest

    You can get an idea of which major circuit block the problem is in with a
    few voltage measurements. First, a caution about this instrument; there are
    very high voltages running around inside, and they can be lethal (that means
    that they can kill you).
    First, the obvious thing to check is the power supply voltages. Start with
    the AC line fuse. There will probably be test points in the vicinity of the
    power supply. Check these first, and fix any outputs that appear dead or
    show wrong voltages. Also, while you're taking a first look around, make
    sure that the CRT filament is lit up. If it isn't, then the CRT and the
    power transformer are suspect (don't forget to check the power switch).
    I assume that you have no schematic for the unit. That means that you don't
    know which pins on the CRT the deflection plates are connected. Usually,
    they are fed by very well insulated wires that stand out in the open, not
    dressed close to the chassis. Check voltages at the wires coming from the
    vertical amp. These voltages should be very close to the same. They will
    likely be at a high potential (200-400 volts). If they are not very close
    (within a few volts), then the problem is likely in the vertical circuit.
    Do the same check with the horizontal amp. Again, voltages should be pretty
    close. You will have to disable the sweep to make sense of this
    measurement; set the Time/Div switch to X-Y, or whatever function it has
    that disables the sweep.
    If these voltages are OK, see if you can find a test point for the high
    voltage. It should be available as a divided voltage, so you can check it
    with a multimeter. If there is no test point, you will need a high voltage
    probe to check the CRT anode voltage at the HV button. Be very careful
    here. Turn the scope off, connect the HV probe, then turn the scope on.
    After checking, turn the scope off before removing the probe. Obviously, if
    the HV test point, or the HV probe reads 0V, then the problem is in the HV
    section.

    If all of the above show no discrepancies, then the problem may be in the
    sweep circuit. Probably an easy way to check the sweep circuit is by
    setting the sweep time switch to a low sweep speed, such as 1 sec/div. Then
    you can watch the sweep building on your voltmeter.
    Without a schematic, that's about as specific as I can get. You should be
    able to get the service manual from Leader.
    --
    Tweetldee
    Tweetldee at att dot net (Just subsitute the appropriate characters in the
    address)

    Time is what keeps everything from happening all at once.
     
  4. Eric

    Eric Guest

    I has a Leader 1040 40 MHz oscillope has similar problem. End up I need to
    re-solder the entire circuit boards. Is your oscillope made by Goldstar
    under Leader licence? Try to check is there any cold solder joints.


    Good luck


    Eric
     
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