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Toshiba Qosmio X305-Q701 AC power adapter problem

Discussion in 'Laptops' started by Aaron, Mar 20, 2009.

  1. Aaron

    Aaron Guest

    While using my Toshiba Qosmio X305-Q701 the other night my display went
    from 'running on AC' bright, to 'running on battery' not so bright.

    It does run on battery; I had shut down the computer, then restarted it
    on battery long enough to copy some needed files, then re-shutdown.

    Research in this newsgroup and on the internet shows that I either have
    a dead adapter or a loose internal power connection.

    Using a multimeter I checked the voltage at the tip of the DC plug. The
    rated voltage is 19 VDC, but I only get a 160 mV. The strange thing is,
    I get 160 mV *consistently* and repeatably. If I got zero volts I could
    easily say "dead brick".

    Is it possible that the adapter puts out 160 mV until it senses it is
    plugged in to a real load, then jacks up to 19 V? Or is it just a dumb
    brick that should be putting out 19 volts regardless of it being plugged in?

    Any other suggestions for home diagnostics I could try before taking it
    in for repairs would also be welcome.
    Aaron, Mar 20, 2009
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  2. Aaron

    BillW50 Guest

    In Aaron typed on Fri, 20 Mar 2009 00:26:15 GMT:
    It could be a smart brick and waiting for a load. But since your laptop
    doesn't see the brick either, it is a pretty good bet it died. And since
    they are pretty cheap anyway, it is about as cheap as you are going to
    get to find out the answer. Sorry I can't tell you more unless you want
    to disassemble the laptop. Or cut into the cord to measure the voltage
    under load.
    BillW50, Mar 20, 2009
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  3. Re: "Research in this newsgroup and on the internet shows that I either
    have a dead adapter or a loose internal power connection."

    There are other possibilities, but by far those are the most likely.
    But not the only ones.

    Re: "Is it possible that the adapter puts out 160 mV until it senses it
    is plugged in to a real load, then jacks up to 19 V?"

    That is possible, depending on the design of the power supply (AC
    adapter). But I think it's unlikely, I think it's more likely that you
    have a bad adapter. It would be best to test the adapter with at least
    a bit of load. Get a 180 ohm resistor and put that across the adapter
    output, then measure the voltage across the resistor. [You could also
    use a 12 volt light bulb (car lamps are 12 volts, just get an interior
    or instrument panel bulb (not a headlight)); it will burn out fairly
    quickly, and it will be VERY bright, but it will probably not burn out
    instantly. If it doesn't light AT ALL, then the adapter is dead.] A
    180 watt resistor will draw about 2 watts (so get a 2 watt resistor) and
    will get kind of warm.
    Barry Watzman, Mar 20, 2009
  4. Aaron

    Aaron Guest

    While using my Toshiba Qosmio X305-Q701 the other night my display
    Barry also suggested testing under, load with a resistor or auto lamp,
    so you both are thinking on he same line. Sounds like a trip to Radio
    Shack is in order.

    Many thanks.
    Aaron, Mar 20, 2009
  5. Aaron

    Aaron Guest

    Re: "Is it possible that the adapter puts out 160 mV until it senses it
    Testing under load is something I can manage. :)
    Now for a trip to Radio Shack, or Auto Zone.

    Many thanks; I'll post to let you know how it works out.
    Aaron, Mar 20, 2009
  6. Aaron

    BillW50 Guest

    In Aaron typed on Fri, 20 Mar 2009 06:07:04 GMT:
    The kicker of course, if it is a smart adapter... it may not fire up
    with just any load. As some of them need to be told from the load who is
    connected. Meaning am I connected to a Toshiba model that I am safe to
    run with? Of course, a lamp or the wrong laptop won't answer or answer
    incorrectly. So that may tell you nothing.

    Also Barry must be talking about a 180 ohm resistor @ 2 watts instead of
    a 180 watt resistor. As resistors in that wattage isn't really called
    resistors anymore. As they are commonly known as heaters instead. ;-)
    BillW50, Mar 20, 2009
  7. I did say 180 watt resistor in one place when I meant 180 ohm (I said
    180 ohm, correctly, in the first instance).

    MOST (almost all) Toshiba laptops use "dumb" AC adapters with just
    coaxial barrel 2-wire connectors. But there are a few exceptions.

    Barry Watzman, Mar 20, 2009
  8. Aaron

    Larry Guest

    Many switching power supplies used to charge batteries are looking for some
    level of battery voltage before they will turn on. Simply hooking them to
    a resistor does not provide this "Hey, my battery needs charging so power
    me." message. So, the switcher thinks the battery is kaput and doesn't
    power up as it may cause a fire in Li-Ion batteries. It's a fire safety
    issue. We've all seen what can happen to craptops that don't have this
    safety feature.
    Larry, Mar 20, 2009
  9. Aaron

    BillW50 Guest

    In Larry typed on Fri, 20 Mar 2009 16:55:13 +0000:
    Greetings Larry! Yes this is so true. Although Aaron stated that the LCD
    backlight dimmed to battery power status while on AC. And all
    indications was it was on battery power. And even ran it off of battery

    So while the no charge could be a low battery causing the safety
    circuits to refuse to charge the battery. But the laptop switching over
    from mains to battery doesn't sound like the battery. Plus running off
    of battery power alone doesn't sound like a low battery either. Although
    Aaron could prove it by removing the battery and seeing if it will fire
    up. It just might, chances are slim I would think. But still possible.
    BillW50, Mar 20, 2009
  10. NO laptop supply works that way, however. [One proof of that is that I
    don't recall ever having seen a laptop that would not work with
    batteries entirely removed, although there may have been a few at one
    point or another).

    All laptops have a fairly complex and sophisticated switching power
    supply inside the laptop, usually on the motherboard. It supplies all
    of the power for the laptop, including in most cases charging the
    batteries. The external AC adapter is just an input to that supply.
    Barry Watzman, Mar 21, 2009
  11. Aaron

    Aaron Guest

    Using info from posts here and from my...ahem...user's guide, I removed
    the battery for a while (overnight) then plugged in on AC power without
    the battery. To my surprise the little red AC light came on, which it
    most definitely did not do before. I gently wiggled and twisted the plug
    at the computer to see i there might be loose connections inside, no
    change. I unplugged the AC, put the battery in, re-attached AC and let
    the battery charge while running errands. It has been working fine ever

    I thank all respondents who assisted, but now I am totally confused as
    to what the problem was.
    Aaron, Mar 23, 2009
  12. Aaron

    BillW50 Guest

    In Aaron typed onn Mon, 23 Mar 2009 01:43:32 GMT:
    Greetings Aaron! That is completely understandable! As you are dealing
    with digital electronics. And in the simplest terms, digital electronics
    is nothing more than just a series of zillions of electronical switches.
    And pretty amazingly, they all work all according to plan 99.999% of the
    time. Although once in a blue moon, a stray electron, a gamma ray, a
    ghost, a fubar, or something else unexplainable causes the near
    impossible to happen. One darn switch gets toggled to the wrong

    When this happens, one just needs to just reboot and the problem
    disappears. Although there are two kinds of reboots. One is a warm
    reboot which most people know about. And the other is a cold reboot (the
    master of all reboots). Which requires all traveling electrons to stop
    moving about and all circuits to be neutralized so that all of the
    electronic switches can be reset. By removing all power (including the
    main battery) performs this cold reboot. And you fixed it by performing
    a cold reboot. Congratulations! ;-)
    BillW50, Mar 23, 2009
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