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Can You Tell Before Resoldering If Motherboard Is Damaged?

Discussion in 'Laptops' started by mutefan, Dec 18, 2007.

  1. mutefan

    mutefan Guest

    Thanks to posts here, I've read up on resoldering DC jacks in general
    and Lenovo ThinkPad's specifically. I came across a link that said
    that you should prepare yourself for the DC resoldering not to work,
    as the shorts/overheating that probably have been going on way before
    your laptop broke probably damaged the board.

    Is there any way of determining before going through the trouble if
    the board really is damaged?
    mutefan, Dec 18, 2007
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  2. mutefan

    BillW50 Guest

    typed on Mon, 17 Dec 2007 17:59:39 -0800 (PST):
    Being a retired electrical engineer I can safely say that a motherboard
    can be damaged do to poor connections. But do to the supply line, I
    would seriously doubt that would come up a lot. And I like to know where
    you have heard this, so I can research it. What is more likely IMHO is a
    run is broken in a multilayered board. Which would be very hard to fix
    even for a professional without schematics. The last schematics I had
    seen for a computer was for the Commodore line. Which was about 20 years
    BillW50, Dec 18, 2007
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  3. mutefan

    Phil Sherman Guest

    Damage to traces on the top and bottom of the board should be visible.
    Unfortunately, most modern boards are multi-layer boards which have
    additional traces embedded between layers of substrate. If an internal
    trace has been damaged, there's no easy way to detect it.

    I'd still try to repair it. Use high quality repair tools; an AC powered
    vacuum solder remover and a miniature soldering tool designed for
    working on circuit boards to make your repairs. It's easy to overheat a
    circuit board and do more damage when trying to remove components.

    Phil Sherman
    Phil Sherman, Dec 18, 2007
  4. mutefan

    mutefan Guest

    Phil or Bill: Do either of you know where you can find *photographs*
    of laptop "guts?" I took the Thinkpad apart to look at the DC solder;
    and to be honest, the solder at the base of the DC jack looked pretty
    good. (Bill, if you google "DC jack" and "broken laptop," you'll find
    tons of stuff.

    You're right when you say that the modern boards are multi-layer. I
    don't see how it would be possible to repair this particular system
    (Lenovo) even if I could locate the short. I wish there were LOTS
    more photographs of laptop interiors online. Thanks.
    mutefan, Dec 18, 2007
  5. mutefan

    BillW50 Guest

    typed on Tue, 18 Dec 2007 14:34:43 -0800 (PST):
    Most of the best places is on eBay or other sources which sells
    motherboards is what I have found. But they don't tell you much. But it
    Okay thanks!
    That is a tough one. As schematics are not freely available as they were
    once had been. The only big reason for the secrecy AFAK is to keep
    others from repairing them.

    OTOH thinking about your problem. Even though your solder joints looks
    fine. The DC jack itself could be bad. As contact switches and jacks can
    easily go bad do to this. As what are the symptoms? As that could tell
    us a lot.
    BillW50, Dec 19, 2007
  6. mutefan

    mutefan Guest

    You could say that again! The internet is worthless, entirely
    worthless, in the end. The most important things you search for, you
    end up searching forever and not finding it. You'd think I was
    looking for the schematics to the NORAD facility or somehting.
    This gave me a lot to think about. 1) The freezes started when my
    generic AC adapter was "giggled" certain ways. 2) Progressed to
    regular freezes, so that a friend who's a computer consultant thought
    Windows XP was the problem; but all diagnostic were okay. 3) Freezes
    intensified to the point where boot would not/will not occur. 4) I
    tore the laptop apart today, and I'm wondering seriously if dirt as
    well as shorts can destroy a laptop. You'd have think I ate five
    Thanksgiving dinners on the keyboard, there were so many crumbs in
    it. (And I'm not a big one for food and drinks anywhere near the
    laptop.) But the crumb-infestation was positively gnarly. 5) When
    finally uncovered, the DC jack looked fine, but now I'm wondering if
    the generic AC giggle/freeze maybe did something to the contact, not
    the solder joint.

    Thanks again!
    mutefan, Dec 19, 2007
  7. mutefan

    BillW50 Guest

    typed on Tue, 18 Dec 2007 17:19:06 -0800 (PST):
    Actually getting the schematics for NORAD might be easier. ;)
    Oh? I also bought a generic AC adapter. It works fine except it isn't UL
    approved. I thought no problem, what is the big deal? Well guess what?
    Fire it up and most FM and TV signals within the house gets blanked out.
    Luckily I also have the original as well.
    Oh no!
    I have never seen dust and dirt cause a problem. But I have heard this
    from tons of people and I don't doubt it for a second. Although I am an
    excessive hand washer. As I feel the need to wash my hands like once an
    hour. The good news is that I never had a remote control or keyboard
    ever fail on me yet. Even 2 decades later with heavy use. Yet my ex,
    they couldn't last a few months and they were acting up already.

    I personally don't have a problem eating and drinking around my
    computer. Luckily no problems to date. Although if I eat something, I
    feel I can't touch the keyboard (or a remote control) until I wash my
    hands. At least not with the fingers that touched food anyway. I dunno,
    maybe just a coincidence.
    I dunno? It is possible that the generic plug dimensions (which is
    pretty common for generic) isn't exactly the same size as the jack
    dimensions. Which can cause contact problems. I was hoping if you told
    us more, it would zero us in on the problem. Although to be honest, it
    is more confusing as to what the cause is if ever. I really hate this! I
    mean I really wish I was there and can see this in action.
    BillW50, Dec 19, 2007
  8. mutefan

    mutefan Guest

    Bill, this is what a "real" computer repairman told me. (I mean
    "real" as "in person".) I insisted the jack was the right one (from
    among the various generic tips to choose from), but he insisted that
    because an adapter tip powered on the laptop didn't mean it was the
    correct one. Man, I could not figure this out, and still don't
    understand how a contact failure could have fried the board.

    Anyway, I still have it ripped apart. I know it'll never work, which
    is why I...washed it. Yep, could not stand looking at that dust a
    single moment longer. The upside is I finally know what the guts of a
    laptop look like and feel called upon once again to attend some
    computer repair school! FWIW, the repair guy agreed that the people
    who do the actual repairing of laptops at service centers/depots are
    minimum wagers off the street. Nothing wrong with that, but you have
    to ask why folk who manage to find schools that actually teach old-
    fashioned soldering are forced to go into business for themselves.

    So I'm gonna keep sniffing around for a DC jack. Thanks again for the
    useful feedback.
    mutefan, Dec 19, 2007
  9. mutefan

    dg Guest

    One, under-voltage (auto-sensing range was incorrect),
    Two, over-voltage (auto-sensing range was incorrect),
    Three, under-amperage (not feeding enough current to meet demand),
    Four, over-amperage (adapter-tip fits, but creates enough of an
    impedance to slow capacitor-response to amperage demands, thus feeding
    in excessive power; some may dispute this is not possible but I've
    seen it happen in certain circuits),
    Five, the adapter may have not been the right length to create a firm,
    solid seat on the plug, thus applying improper tensions--then over
    time, jiggling results in tiny, tiny shorts or breaks in current flow;
    internal capacitors in the on-board power-converter filter these for a
    while, but eventually the circuitry breaks down,
    Six, similar to five but think bigger--damage happens within the multi-
    layered circuit board, from the jiggling--rather than the power-jack's
    soldering, as is more common.
    "washed it" ? As in, threw in the towel, it's a wash, washed it, or as
    in, soap-and-water washed it? :)
    Well, it's hard to stay in business doing soldering--possible as a
    side-job, but most people just aren't willing to pay professional
    rates for computer repairs, as it can quickly exceed the advertised
    cost of a cheap PC.
    Service-centers, depots, and manufacturers themselves hire the
    cheapest labor available and teach them just enough to do a gets-by
    job on a small portion of a larger task, so that the person does not
    become too generally skilled to be kept in a bottom-of-the-barrel
    payroll position. Read "The Six Sigma Way" and think about it, and
    you'll have a very good idea of how GM and Motorola screwed themselves
    royally by applying it, until they renounced its teachings. (And yes,
    they both did adopt it and failed badly until renouncing it, and yes,
    most of corporate America subscribes to it "because the big-boys do".)
    Good luck!
    dg, Dec 24, 2007
  10. To check if your motherboard is damaged or if the DC jack is at fault,
    try using a lab power supply and set its voltage and current levels to
    what the notebook requires. Then connect the black wire to a ground
    point. Connect the red wire to the positive trace on the motherboard
    behind the DC jack. If the motherboard powers on then the DC jack is
    at fault. If it does not power on, then the motherboard has been

    Notebook Solutions Inc.
    kenneth_finch, Jan 7, 2008
  11. mutefan

    Art Guest

    Ken's advice is easier said than done. Some of the damage occurs where the
    power jacks are soldered to the motherboard. In other words, a working AC
    adapter may provide the proper voltage to the power jack, the power jack may
    be fully intact and operational, but the connection between the power jack &
    the motherboard is deficient. The defect may be too small to see.
    Motherboards generally have insulating coatings right up to the point where
    the power jack leads are soldered to the mother board. There is no
    reliable place to connect the "red wire" to the positive trace on the
    motherboard. The leads coming off the power jack are about 1 mm in
    diameter. You would have to scrape off some of the insulating coating,
    somehow create a secure way to provide an electrical connection for both the
    positive and negative leads of your lab power supply while you test whether
    or not the motherboard powers on. If for a moment you have done something
    silly like reversing the polarity of your power supply, your motherboard may
    give off a puff of the proverbial "black smoke" and then you will know for
    sure that it's damaged. Most laptops must be almost completely disassembled
    to allow access to the positive & negative portions of the power supply on
    the motherboard, and disassembly of a laptop is time-consuming and explains
    the relatively high charges for laptop repair. A few laptops have power
    jacks located on an easily removable daughter board which make power jack
    repair much easier, but most do not. If you take care not to allow static
    electricity to hit the parts you are removing, you have a decent idea of
    where the screws, clips & removable subunits are, and if you are gentle &
    meticulous, taking a laptop apart is not a big deal.
    However, removal of a defective power jack from a motherboard is tricky
    in itself without specialized de-soldering tools. Once the power jack has
    been removed & the holes in the motherboard cleaned, soldering a new power
    jack is fairly easy, but the process leading up to it is not.
    I recently "fixed" my Toshiba M35X-S149 laptop which had a defective
    power jack. I found an adequate guide to disassembly of this model on the
    net. I was positive the power jack was the problem, since it had happened
    twice before, with a new motherboard & then a resoldered power jack repair
    which did not last. My attempts at desoldering weren't of much use until
    I sawed the old power jack into 3 pieces. Then I was able to desolder the
    remaining debris. I simply soldered two new leads of flexible wire direct
    to the motherboard, put a loop in the wires for strain relief, brought the
    wires out the back of the case so that they formed a "dongle", then soldered
    a "chassis-mount" power jack (one that fit my AC adapter) to the ends of
    the wires. To my surprise, the computer booted up, and is still working a
    week later. My work looks like hell. If you dare to go far enough to
    connect test power leads directly to your mother board to see if it is
    damaged, you might as well attach a new pair of power leads as I did.
    I did my repair fully aware that I might fatally damage the motherboard
    in the process, but I was unwilling to have another "professional repair" in
    a machine out of warranty.
    I have read that power jacks for Lenovo laptops are not available.
    Lenovos have very unusual looking power jacks. If you care as much about
    appearance as I do, it would be fairly simply to bypass the Lenovo power
    jack and replace it with a more commonly available power jacks. You would
    have to replace the Lenovo power plug with a plug to match the new power
    To check if your motherboard is damaged or if the DC jack is at fault,
    try using a lab power supply and set its voltage and current levels to
    what the notebook requires. Then connect the black wire to a ground
    point. Connect the red wire to the positive trace on the motherboard
    behind the DC jack. If the motherboard powers on then the DC jack is
    at fault. If it does not power on, then the motherboard has been

    Notebook Solutions Inc.
    Art, Jan 8, 2008
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