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54520A repair

Discussion in 'Electronic Repair' started by [email protected], Apr 16, 2007.

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  1. Guest

    Hello all,

    I recently purchased a broken 54520A hoping to be able to repair it.
    The seller said that the screen was faulty. However, after the
    oscilloscope arrived, I saw very soon that the problem was not the
    screen but something else.

    When the oscilloscope boots, the fan turns on and all the indicators
    on the front pannel light-on. But it hangs there. No keyboard response
    and nothing displayed on the screen. However, the screen is working,
    as when I turn off the device, sometimes I can see the beam on the
    display and some noise.

    The indicators keep lighted on until you turn the oscilloscope off

    Could anybody help me? Its a great oscilloscope, but it just does
    not work :-(

  2. James Sweet

    James Sweet Guest

    I assume this is a DSO? Start with the simple stuff, check the power
    supply voltages, see if the CPU clock is running, have a look at the
    reset line, that should provide some insight.
  3. Guest

    Yes, its an HP 54520A digitizing oscilloscope.

    I will check if all the voltages are OK. According to the service
    manual I have to search around for a 2 Ohms 25 Watt resistor to load
    the power supply.

    I will post my results here.

  4. Here are aso some experts to find:

  5. Guest


    There may be a lithium cell which is used to maintain the static ram
    where calibration data is stored. In the 5454x series of 'scopes the
    system locks up exactly as you describe when the lithium cell is
    discharged. This seems to happen about 15 years after manufacture.

    The service manual makes no mention of this problem!

    I had a similar problem with my HP 54542A 'scope and another poster
    had this problem with his HP 54540.

    Replacing the lithium cell and running the self-calibration fixed the
    problem for both of us.

    For more information, search this group ( for

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