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laptop power issue

Discussion in 'Troubleshooting and Repair' started by riget, Mar 12, 2010.

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  1. riget

    riget

    23
    0
    Mar 12, 2010
    Hi all, first post and I've got a problem with a laptop, a toshiba u300, I hope you can help me with.
    I have little electronics knowledge, but am willing to learn.
    The problem is, the laptop will not turn on unless I remove the power adapter and battery and hold the on button for about 20 seconds, the laptop runs fine then but every time I turn it off it doesn't start again, it's dead, no lights no nothing, I have stripped it down and have found that if I remove the battery and put a voltmeter on a capacitor, it reads 12v then goes quickly down to around 2v, then the laptop will boot.
    The battery has 9 connections, I have found that when the laptop will not boot, 2 connections have 12v all the others have zero, when it will boot, 2 have 12v, 1 has 0.2v, 2 have 3-4v.
    So with my little knowledge it seems static electric stops the laptop from booting, I don't think it's the battery as I also have the problem using just the power adapter.
    I hope you understand my rather long problem and can give me some idea of what can be the cause.
    Thanks
    riget.
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    One thing that can prevent normal boots is if the CMOS battery is run down. It can be in the form of a normal coin battery, a small cell-pack, or a battery-backed Clock/RAM chip.
     
  3. riget

    riget

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    Mar 12, 2010
    Yes I did read that, and it was bad, I fitted another but I still have the same problem.
    Thanks.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,291
    2,727
    Jan 21, 2010
    Sorry, can you explain that again. It sounds like you have to remove boththe power adapter *and* the battery to start the laptop.

    That would leave it with no power source at all.

    Presumably you insert either the battery or the power adapter again before you try to turn it on (which one or is it both?).

    How does the machine shut down? Do you shut it down, or does it initiate its own shutdown due to low power, hibernate, or just stop as the power fails?
     
  5. riget

    riget

    23
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    Mar 12, 2010
    I have to remove the adapter and battery so there is no power source, hold the on button or touch a capacitor with a voltmeter, then either replace the battery or adapter and start the laptop.
    I shut it down, it runs fine and the battery charges ok, it can run on battery only or adapter only, or on both as normal.

    Thanks
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,291
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    Jan 21, 2010
    Interesting.

    When you say
    do you mean any capacitor, or a specific capacitor. Is the multimeter on a voltage or current setting? are you connecting across the capacitor?
     
  7. riget

    riget

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    Mar 12, 2010
    I was just checking around with the voltmeter on 20v dc, an area around the power socket where the largest capacitor was, had battery 12v or adapter19v voltage, it's anywhere in this area, the voltmeter is connected to an earth area of the board, if no power is connected then when I touch with the + of the voltmeter a chip(capacitor) I not sure of all the items, then that's when the voltage drops and the laptop will boot.
     
  8. riget

    riget

    23
    0
    Mar 12, 2010
    In the pic you can see the battery connection to the lower right, above that is the memory chip, then to the left is the main power socket(white ablong) then to the left and down is the largest capacitor(about 10mmx10mm)silver/black, the capacitor above and to the left silver/purple, does not have any volts, the little chips around the silver/black capacitor, that look like capacitors?(I'm not sure) the brown one's, have the same voltage, and if I touch any of these without the power connected then it drops from 12v to 2v quickly.

    Now I'm a mechanic so my knowledge is limited, but it seems something is storing the volts that stop the laptop from booting, even connecting a voltmeter allows it to work,
    If I could solder a mini voltmeter to one of these chips and to earth I think it would work, is there such a thing?

    [​IMG]
     
  9. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Sorry, but the picture is not clear enough to tell much.

    What happens if you shut down, remove the battery and external power, do NOT touch any capacitors, let it sit for 15 minutes, then connect the battery and/or the power and turn it on? Does it power up then?

    I would also like to repeat Steve's question: Does the machine shut down on its own or do you do a Windows shutdown? If it a shutdown or a hibernate?

    ---55p
     
    Last edited: Mar 13, 2010
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,291
    2,727
    Jan 21, 2010
    That's kinda fuzzy. Can you try to get a better picture. Even if you have to get a little further away to get it in focus. Ideally we should be able to read the writing on the components.

    It's really hard to tell what things are, but the big round silver things with the coloured segment are electrolytic capacitors. The things with three or more leads are semiconductors of some type (they are usually black). The rectangular black things with leads at either end are likely to be resistors or diodes. The yellow coloured things with connections at each end are likely to be ceramic capacitors (if small and thin) or tantalum capacitors (if larger and blocky).

    Of course there are exceptions since electronic components are not coded by body shape or colour :)

    Reading your description, it does sound like you have identified capacitors.

    A voltmeter is really (to the circuit being measured) a high value resistance, so I guess you could connect a high value resistor across one of those capacitors.

    The question though is will that resistor disrupt the normal operation of the circuit, and why is it needed.

    It is not possible to determine exactly what this part of the circuit is doing, but it's probably a voltage regulator. I would expect to find an inductor there somewhere.

    Until you can get a better picture though, anything else is just crystal ball gazing.

    edit: Yeah, as 55p says, but if leaving it 15 minutes doesn't help, try leaving it 24 hours with the battery and charger disconnected.
     
  11. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Can you be sure that you fitted it correctly? Are you sure that you installed the new battery and did not accidentally install the old battery and throw away the new one? Is the new battery the correct model and correct voltage?

    Here's what could be happening.

    All your problems were because the battery was dead.

    You thought you replaced the battery, but in reality you did not.

    The symptoms continue because you really did not do anything.

    A dead or incorrect battery would explain everything.

    ---55p
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,291
    2,727
    Jan 21, 2010
    I've not met a laptop that would fail to operate when connected to the charger, but with the battery removed.

    I *think* it has been mentioned that the laptop does not work in this configuration, but I'm prepared to be contradicted.
     
  13. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    If locating the real fault turns out impossible I guess you could band-aid the situation by soldering in a high-value resistor to imitate the voltmeter action.
     
  14. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    One other data point request: When you get the laptop to boot by discharging the cap, does the laptop retain the correct date and time?

    ---55p
     
  15. riget

    riget

    23
    0
    Mar 12, 2010
    I'll answer all questions best I can, and try to get a better pic later.
    I turn the laptop off, it does not shut down by itself, when it's running it's fine.
    If I leave it with the battery and charger disconnected for 15 mins it will not boot, if I leave it for 24 hrs it will not boot, maybe a bit longer and it will boot.
    The new bios battery is fine and giving 3v as normal, I've not checked if it keeps time and date, as I've not been connecting the keyboard.
    Thinking about fitting a resistor, it wont work because the capacitors have battery voltage 12v, when the laptops turned off, I have to remove the battery for the voltmeter to discharge the voltage.

    Another thing is why does the battery have 9 connections? It must talk! to the laptop, could the battery be faulty?

    Thanks for all the help.
     
  16. riget

    riget

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    Mar 12, 2010
  17. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    The 9 pins include 2 each of power and ground and 2 for SMBUS. I am not sure what the remaining 3 are. There may be a thermister and a present signal, or 3 each of power and ground and a present. The SMBUS is for the battery to talk to the laptop. If you have the battery out of the system, then it is no longer talking and should not cause a problem.

    Can you please confirm that it is shutdown and not hibernate. Assuming that it is shutdown.....

    Something does not add up. The capacitor you are shorting is an aluminum cap, likely a cheap one. It can not retain its charge for 24 hours, let alone 15 minutes. If the battery and the power are disconnected, where is it getting its power?

    Can you please confirm that the voltage across the cap is still 12V 15 minutes after it has been removed from all power and battery pack?

    Can you please confirm that you are measuring the voltage across the cap and not accidentally shorting anything?

    Without going into a lecture about how Intel chipsets do power state management, there are basically signals that come of the ICH that control the power switches that put the motherboard into the G3 state. If the signal or the MOSFET is bad, it is possible that things do not shut down in order and the power state controller gets completely hung up. What you are accidently doing is shorting the CMOS battery to ground, which resets the power state machine and order is restored to the universe.

    That is why it would be good to know if the date is being reset.

    ---55p
     
  18. riget

    riget

    23
    0
    Mar 12, 2010
    The battery has 2 power and 2 earth, these are the outside 2 either side.
    It's the middle 5 I don't know, I'll say what they give, left to right,
    when the laptop will boot, 3v, 3v, 2v, 0.2v, 0v
    when it wont boot, 0v, 0v, 0v, 0,2v, 0v

    I can confirm it shuts down, it doesn't hibernate,sleep, doze off, it shuts down.

    The voltage across the cap is 12v, it is also 12v at several points around it, the 3 yellow/brown chips, and some of the black chips, it doesn't matter where I put the voltmeter when the battery is removed, I get the same result, so they must all be linked and possibly none are responsable for the fault?

    Can it be that the battery should discharge the voltage(if that's what's suppose to happen) and it's not doing it? It charges and runs the laptop fine, but maybe it does more than I think.

    Sorry if what I say doesn't make much sense, but I'm not that electronic minded, if it was a car I'd fix it with a hammer lol.
    Thanks.
     
  19. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    The two pins that are 3V are the SMBUS pins. They have a 3V pull-up when they are active. When the system is asleep, the pull-up voltage is removed and they go to 0V.

    The middle pin is likely a thermister. The 0.2V is sense and 0V is ground. The battery voltages all look normal.

    What I simply can not understand is how you could get 12V when the battery and power are disconnected. And how this 12V maintains its voltage long after power is removed. There has to be another power source. Is there any possibility that there is another battery in the system somewhere? Another battery besides the tiny CMOS battery.

    I am out for the rest of the day so I will have to put this off till tomorrow. Everyone else is welcome to take a crack at this.

    ---55p
     
  20. riget

    riget

    23
    0
    Mar 12, 2010
    I hadn't touched the laptop all day, it's been left with no battery in it, I just went to boot it and it wouldn't, it has no other power apart from the 3v bios battery.
    Reading up on capacitors it seems they can hold voltage for months or even longer.
    I'm not sure it's 12v after a day or more, I've only been checking while I've been working on it, maybe it drops but the laptop still doesn't boot unless I hold the on button for several seconds.
    Thanks.
     
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