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random use of different notebook transformers

Discussion in 'Electronic Repair' started by JWBH, Mar 15, 2007.

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  1. JWBH

    JWBH Guest

    My young son's friend came around to our house the other evening with his
    notebook pc. The friend's battery started running low, so my son took the
    transformer from my wife's laptop and plugged it into his friends computer.

    I was horrified that he hadn't checked the voltage the amperage or the
    polarity. He knows more than me about computers, but was he right to not
    check these things or does a few volts, the polarity or the likely
    difference in amperage between notebook computers not matter much.
    grateful for other opinions on this. thanks.
  2. It matters a lot.
    The wrong voltage or polarity could potentially destroy the laptop, the
    power supply or both. The wrong size plug could damage the plug or the
    Using an adapter with the correct voltage, plug and polarity but not
    enough current probably would not work well or has a chance of
    overheating the power supply as it tries to provide more current than it
    is designed to.
    In all or most modern laptops, the power supply is integrated on the
    motherboard so the cost of repairing the damage could be very high.
  3. I just cut and strip the end of an extension cord and put the wires in
    whatever holes look convenient.

    Obviously you know the answer.
  4. mike

    mike Guest

    It's reckless to use the wrong adapter. Will probably work over a big
    range of voltages, but it's generally a BAD idea.

    But did you check your assumptions before jumping to conclusions?
    It's possible that he's done that a bunch of times with that adapter
    and lapotp. If you check it once, probably don't need to do it again.
    Maybe what you judge as reckless might just be a good memory ;-)
    Yeah...what am I thinking...
  5. Humorous post ... although you might not have intended that. Old farts are
    often dismayed when their old-time logic and knowledge crashes and burns in
    front of the kids that they raised. It's OK BTW; they are more tolerant.
  6. PeeCee

    PeeCee Guest


    With respect I have not seen a Laptop/Notebook with the 'Power Supply'
    integrated on the motherboard since the days of 486's (Toshiba for example)
    'Power Supply' being the components that convert the AC mains from the wall
    socket to the DC voltage required to run the Laptop / Charge it's battery.
    These days universally an 'external' power brick or 'transformer' as
    described by the OP.

    Quite agree with your first two points though.

  7. WhzzKdd

    WhzzKdd Guest

    I believe the point he was trying to make isn't the power transformer and
    ac/dc conversion being on the motherboard of the laptop, but with the
    charging circuits, and the voltage converters/regulators, etc., being
    integrated internally in the laptop. I've seen a number of adapters with
    multiple voltage outputs, but more and more I see these single voltage
    barrel plug connectors with 19V or whatever. Knowing that the components in
    the PC actually run primarily on 5 and 12 volts, the conversion is being
    done in the laptop. Mess that up, and you've got an expensive repair.
  8. WhzzKdd

    WhzzKdd Guest

    Love it! That would be quite the light show, eh?
  9. mike

    mike Guest

    I once bought a power brick at a swapmeet. Put it on the voltmeter.
    Measured zero CD volts, but it shocked the pee out of me.
    Turns out someone had tied the AC mains to the output and put a postit
    note inside saying, "F...You!". Glad I tested it first.
    I know who sold it to me, but he's much bigger than I am ;-(
  10. WhzzKdd

    WhzzKdd Guest

    Yow! I think I'd be pretty pissed <g>
  11. James Sweet

    James Sweet Guest

    Yikes, I'd think that would be a criminal offense, someone could be killed.
  12. At some time in 1962, some Japanese EE designed the first piece of
    crap with one of those tubular jacks.

    If he would have thought ahead, he would have realized the huge
    problem he was creating.

    It seems nobody went to the trouble of coming up with some sane
    standard for these connectors, so we ended up with idential-looking
    connectors, some with AC, some with DC, of either polarity, and
    unfathomable amperage. I have a weed-whacker charger that puts out
    1.5 volts, and a HP printer brick that puts out 37 volts. Madness.

    You may be able to luck-out, as most laptops have very flexible power
    supplies,a s they haev to be able to run off batteries, charged or
    almost discharged. So most laptops can tolerate a modicum of voltage
    ranges. Many even have a diode or four to protect against reverse

    But in general it's best to make mismatching difficult to impossible.
    Like putting green paint on the connector and on the laptop socket.
    And blue on the printer and printer cord. And so on, all the way
    through your modems, routers, bridges, usb hubs, weather stations,
    radios, boomboxes, and whatnots.
  13. Robb

    Robb Guest

    1962! hah.

    I had a 1960 five -or- six-transistor radio with an optional external
    power cord/wire/plug-in device thingy. Matched perfectly with the
    input of an immersion coffee re-heater, but that only worked once. :/
    Should we have our right legs tattooed "right" and the same for our
  14. A friend had to go in for an operation on her foot. She and another friend
    wrote on the other foot in felt pen, "WRONG FOOT".

    Guess which one they operated on?

    USA: "We have the finest xxxxxxxxxx in the world"!

    Yeah, right.
  15. WhzzKdd

    WhzzKdd Guest

    Yeah, but can't you just /smell/ "lawsuit"? <g>

    Bet they got the correct foot fixed for free, plus some extra pocket cash.
  16. WhzzKdd

    WhzzKdd Guest

    Don't you be color coding MY whatnots! <g>

    Okay - I know what you mean, and totally agree. While there have been a good
    number of altered barrel connectors (different OD, different post ID, some
    color coding, etc.) it's still way too haphazard.

    Truth is, in a pinch, I've used some pretty weird connector combinations
    myself...whatever was in the junk box at the time ;)
  17. Have a friend who bought a pickup truck with his part of the settlement.
    Have no idea what the lawyers bought. His knees weren't labeled though. IIRC
    he let the same doctor do the correct knee. At least he knew he had good
    malpractice insurance.
  18. Guest

    Guest Guest

    with so many proprietary stuff around, u lucky u didnt have to buy another
    replacement laptop!
  19. WhzzKdd

    WhzzKdd Guest

    Tested and proven <g>! Still...I'd be a little concerned...
  20. Hi!
    There's not a "whole" line voltage to DC power supply in a modern laptop,
    but there is very often a power supply known as a "DC-DC converter" that
    takes the single voltage from the power adapter and provides all the
    different voltages the computer will need. This supply usually also has the
    majority of the battery charging circuitry on it.

    Some (very few) laptops actually have power bricks that put out more than
    one voltage. I haven't seen any recent ones, though.

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