power supply causing network failure? - Debian

This is a discussion on power supply causing network failure? - Debian ; Hi all, I have just bought a new power supply for my HP nx7010 laptop (the old one seems to have a broken wire on the low voltage side meaning it sometimes doesn't actually deliver power... bad). Unfortunately, the new ...

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  1. power supply causing network failure?


    Hi all,

    I have just bought a new power supply for my HP nx7010 laptop (the old one
    seems to have a broken wire on the low voltage side meaning it sometimes
    doesn't actually deliver power... bad).

    Unfortunately, the new power supply doesn't seem to work properly with the
    nx7010.

    The laptop detects that it has been plugged in to a power supply (LEDs change
    as usual on the front of the case) and the battery will charge up. However,
    the built-in network card in the laptop (which uses the 8139cp driver)
    doesn't work properly when connected to this new power supply. With the new
    power supply attached, I consistently have a 15-20% packet loss (making the
    network unusable); on battery or on my old power supply, I have 0% packet
    loss.

    The problem is persistent across reboots and there is absolutely nothing
    appearing in dmesg or any of the other logs to help me work out what is going
    on. I can make the problem go away just by unplugging the new power supply
    either from the laptop or the wall socket, but that's not really an option. I
    don't know whether the ipw2100-based wireless network is also similarly
    affected as I don't have a wireless network where I am at the moment.

    Has anyone ever heard of anything so strange? Any clues for a work-around?

    cheers
    Stuart


    --
    Stuart Prescott www.nanoNANOnano.net


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  2. Re: power supply causing network failure?


    On Aug 21, 2006, at 6:29 AM, Stuart Prescott wrote:

    >
    > Hi all,
    >
    > I have just bought a new power supply for my HP nx7010 laptop (the
    > old one
    > seems to have a broken wire on the low voltage side meaning it
    > sometimes
    > doesn't actually deliver power... bad).
    >
    > Unfortunately, the new power supply doesn't seem to work properly
    > with the
    > nx7010.
    >
    > The laptop detects that it has been plugged in to a power supply
    > (LEDs change
    > as usual on the front of the case) and the battery will charge up.
    > However,
    > the built-in network card in the laptop (which uses the 8139cp driver)
    > doesn't work properly when connected to this new power supply. With
    > the new
    > power supply attached, I consistently have a 15-20% packet loss
    > (making the
    > network unusable); on battery or on my old power supply, I have 0%
    > packet
    > loss.
    >
    > The problem is persistent across reboots and there is absolutely
    > nothing
    > appearing in dmesg or any of the other logs to help me work out
    > what is going
    > on. I can make the problem go away just by unplugging the new power
    > supply
    > either from the laptop or the wall socket, but that's not really an
    > option. I
    > don't know whether the ipw2100-based wireless network is also
    > similarly
    > affected as I don't have a wireless network where I am at the moment.
    >
    > Has anyone ever heard of anything so strange? Any clues for a work-
    > around?


    It sounds like :
    a) Your new power supply has a grounding problem, or a noise problem,
    thus introducing noise onto the Ethernet via the internal power bus.
    b) More likely - your old supply caused damage to the internal power
    filters and/or voltage regulators in your laptop and thus the
    Ethernet chipset is seeing dirty power when connected to your new
    supply.

    Or a combination of the two, or something similar. Additionally some
    switching supplies throw a lot of RF noise, if your Cat 5 cabling is
    acting as an antenna at those frequencies, you could be "struggling
    through the noise" being created by the new supply.

    I'd start with the simplest solution -- return the new supply and get
    a new one. After that, it gets a lot more difficult to do much. If
    you can find one of those Cat 5 cables with big round torroids built
    into each end (Cisco SoHo cheap routers used to ship with them, for
    example) you might try one of those to see if the noise clears up or
    gets markedly better. If not then the expensive fix (having a
    qualified service tech look into the guts of the laptop) awaits,
    probably.

    If you still have the old supply and you find the *right* service
    tech who's actually had more than five minutes of electronics
    training, and isn't just a part-swap monkey, they might be able to
    figure out what damage would be most likely if the manufacturer
    actually gives them any schematics to work from... probably not
    nowadays... everything is "throw-away" or "field-replaceable
    units"... it's not cost-effective to troubleshoot to the component
    level anywhere but a bulk board repair shop anymore.

    --
    Nate Duehr
    nate@natetech.com




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