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Thread: Toshiba T1900C

  1. #11

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    Quote Originally Posted by DankEngihn View Post
    Depends on the multimeter you have.

    They're not electrolytic capacitors, they're SMD tantalum capacitors, which when they fail, fail short.
    ah, I see. Thank you for explaining this out.

    Quote Originally Posted by DankEngihn View Post
    Have you tried powering up the board with nothing else connected? Just the two boards and a charger?
    Yes, all the boot attemps I described here today I did with the two boards only + charger.
    Well, I did have the screen connected as well. I will make one more attempt unplugging the screen
    and see if there is any change in the DC IN led behaviour.

  2. #12

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    Quote Originally Posted by VintageVic View Post
    I cant see any electrolytic caps on the motherboard.
    I'm quite novice with electronics, is it possible to measure ESR with just multimeter ?
    In general, testing capacitors is not a simple task. A multimeter is not normally sufficient on its own. An ESR or capacitance test would be much more definitive. Overall it's way more involved than it might seem on the surface. In some cases, removing the capacitor(s) from the circuit is the only tried and true method and that alone can introduce further issues.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  3. #13

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    It's possible for capacitors on the inverter board of the screen to fail.

    If still nothing, try hooking up a speaker to the parallel port. Some laptops emit beep codes from the parallel port

    EDIT: what power supply are you using? Post a picture of it. The DC led can blink like that if it detects abnormal voltage.

  4. #14

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    Quote Originally Posted by DankEngihn View Post
    It's possible for capacitors on the inverter board of the screen to fail.

    If still nothing, try hooking up a speaker to the parallel port. Some laptops emit beep codes from the parallel port

    EDIT: what power supply are you using? Post a picture of it. The DC led can blink like that if it detects abnormal voltage.
    I unplugged the screen and no change in the DC IN led behaviour (one long + three short blinks repeating).
    p-port.jpg

    from t1900c maintenance manual it is revealed, that I could try to construct LED checker for error code. That is then
    plugged to the printer port. I would need to find out how the pins are connected to the leds, then I might construct one.

    And yes, it is still possible, that all this effort is just due to mismatching psu. That is the one I'm using and it is not original to this laptop.
    Toshiba power connector has marking 18V.
    psu.jpg

  5. #15

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    Try hooking 12 volts up to the battery terminals directly, without the charger.

    It's most likely a bad capacitor on the power board.

    EDIT: Make sure you get the polarity right, or it'll cause more issues.
    Last edited by DankEngihn; January 9th, 2020 at 11:53 AM.

  6. #16

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    Quote Originally Posted by Stone View Post
    In general, testing capacitors is not a simple task. A multimeter is not normally sufficient on its own. An ESR or capacitance test would be much more definitive. Overall it's way more involved than it might seem on the surface. In some cases, removing the capacitor(s) from the circuit is the only tried and true method and that alone can introduce further issues.
    Yeah, I was a bit suspecting, that my simple multimeter is not up to the task to measure ESR.
    I might not be either, heh heh.

    I could just pull out more caps from the board and see if anything changes. But perhaps a short break
    to think what is the best course of action is in order. I do not have new spares at the moment and it probably
    will not work either when all caps are pulled out... I might use scrapped atx power supply, if it has matching capacitors
    for a replacement. New caps are cheap to order from china/ebay, but recently it has taken 6-10 weeks before orders have
    arrived here. I'm not in a hurry, but that is a bit ridiculous .

  7. #17

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    Quote Originally Posted by DankEngihn View Post
    Try hooking 12 volts up to the battery terminals directly, without the charger.

    It's most likely a bad capacitor on the power board.

    EDIT: Make sure you get the polarity right, or it'll cause more issues.
    That might not be a bad idea to try!
    wow... but let me take a moment to figure out how to connect 12V to five contacts .
    There is 0,45 Volts across leads marked with + and - . I mean, those two leads that are
    most far from each others. I guess it might be right place to connect +12 and ground.


    batt.jpg

  8. #18

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    Only connect it to the two on the edge!

    In your picture, the far right is negative, and left is positive!

    The middle 3 are ground!

    DO NOT CONNECT THE THREE MIDDLE CONTACTS TO POWER. YOU WON'T HAVE A GOOD TIME.

    Connect it to the terminals on the motherboard. Not the battery.

  9. #19

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    Quote Originally Posted by DankEngihn View Post
    Only connect it to the two on the edge!

    In your picture, the far right is negative, and left is positive!

    The middle 3 are ground!

    DO NOT CONNECT THE THREE MIDDLE CONTACTS TO POWER. YOU WON'T HAVE A GOOD TIME.

    Connect it to the terminals on the motherboard. Not the battery.
    Right! No worries, I gave it a go, connected +12 to the far left (on motherboard) and ground to far right.
    -> still the same behaviour with the LEDs.

    It was a good try anyway, my shaky gut feeling tells me, that if the motherboard was ok, that 19V psu would
    fit it just fine. And I can always try to use ATX psu 12V on the two terminals later also, just to make sure.

    8.jpg 9.jpg

    I made final attempts to pull the two light blue caps one by one and tested after each pull.
    Still no change. I pulled these two, since someone had experienced that these were also bad.

    But, I think I am going to sleep over this now. It's late here and early wake up for work in the morning.
    Thanks again for all suggestions!

  10. #20

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    One last thing. Did you have the power supply plugged in? If so, remove it, and try again.

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