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    HP54520A problem, first hints

    My HP54520A scope is breaking down... After a few minutes of activity it burns the mains fuse (4A 250V). Before I open it for a visual inspection, do you have any hind what might be the problem?

    Maybe something with the PSU, when it is heated?
    A leaky PSU electrolytic? (how to check that?)
    Professional engineering is the top, but amateur engineering is more fun.
    It is when you cross the barrier between these two, that things become really fascinating!

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    Re: HP54520A problem, first hints

    Quote Originally Posted by neazoi View Post
    My HP54520A scope is breaking down... After a few minutes of activity it burns the mains fuse (4A 250V). Before I open it for a visual inspection, do you have any hind what might be the problem?

    Maybe something with the PSU, when it is heated?
    A leaky PSU electrolytic? (how to check that?)
    I did a self test on the menu. All self tests are passed ok.
    The problem blows the fuse after a few minutes/tens of minutes so I cannot test anything.
    Any speculations what might cause such a problem?
    I bet it is something with the PSU
    Professional engineering is the top, but amateur engineering is more fun.
    It is when you cross the barrier between these two, that things become really fascinating!



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    Re: HP54520A problem, first hints

    Some HP instruments have a mains input filter that with age can become internally conductive and blow the mains fuse.
    However, when this happens there is normally bad smelling gas coming out of the filter.
    The solution to that problem is to replace the mains filter. I found one at Mouser for my HP signal generator.


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    Re: HP54520A problem, first hints

    Quote Originally Posted by std_match View Post
    Some HP instruments have a mains input filter that with age can become internally conductive and blow the mains fuse.
    However, when this happens there is normally bad smelling gas coming out of the filter.
    The solution to that problem is to replace the mains filter. I found one at Mouser for my HP signal generator.
    I did not notice any smell though. How can I check this filter for being conductive? Disconnect it from the rest of the instrument and check for conductivity between the mains terminals?
    Professional engineering is the top, but amateur engineering is more fun.
    It is when you cross the barrier between these two, that things become really fascinating!



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    Re: HP54520A problem, first hints

    I've seen that in my HP function generator too. The easy check is to temporarily disconnect it and bypass it. They tend to fail under stress and measure fine at low voltage. I would agree with the PSU diagnosis, does that model have a cooling fan and if so, is it free to spin?

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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