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Thread: laptop problems / power issues

  1. #1
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    laptop problems / power issues

    I had an old laptop that i gutted and everything was working fine with an external monitor. I tried extending the lcd (with cat 5 wires) and hooking that up to the back. Now the laptop doesn't even power up. I have a multimeter (?) but i have no idea what to look for to figure out whats wrong. I am hoping its something i can pinpoint but i don't know how. So my question is, where on the motherboard do i use the multimeter to try to figure out whats wrong. sorry if its a dumb questions. im a newbie at all this.

    thanks.

  2. #2
    Maximum Bitrate Yuriy's Avatar
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    Well, that depends entirely on your laptop's model.
    Tell me, what do you mean by not working?
    Do the fans/hard drive make noise? Any leds lit/flashing? Any sound through the speakers?

    Here is the most likely solution to your problem:

    Cause: you extended the wires going from the LCD inverter to LCD backlight.
    Why not? -the signal coming from the LCD inverter gets weaker when the wires get long.
    Solution: instead of extending the INVERTER<>LCD cable, try extending LAPTOP<>INVERTER cables, this way it will work no matter how long you extend it. The key is to keep the INVERTER<>LCD cables (two of them) as short as possible. Just slap the inverter board to the back of your LCD and forget it

    With that said, I am pretty sure that your laptop works great, only you don't see anything on the screen since your backlight doesn't work. As soon as you do what I said above you will see everything perfectly
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  3. #3
    MySQL Error jcdillin's Avatar
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    Also depends on how far you have extended the lines, lcd signal doesnt like traveling more than 10 feet without shielding, I would also disconnect the lcd from the laptop and try to make sure it works with a external monitor again.

  4. #4
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    addendum

    Thanks guys,
    but that isn't the problem. Something went haywire with the laptop it self, no leds, no noise, no nothing anymore. I might have fried the motherboard is my worry. Just want to figure out how I can verify this or diagnose the problem.

    Another thing was that, the lcd that i extended had 20 pins on the lcd end and 21 on the motherboard. how do i figure out how to wire that?

    thanks guys.

    Its an old 14.1 inch compaq 1700 presario.

  5. #5
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    Sorry to be so annoying, but i just needed to bump this because i am about to buy another motherboard from ebay but i needed help from you guys first.
    sorry.
    thanks again.

  6. #6
    MySQL Error jcdillin's Avatar
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    Does the laptop power on with the lcd and the inverter disconnected?

  7. #7
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    not anymore. no.

  8. #8
    MySQL Error jcdillin's Avatar
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    And you pulled the battery and the power cord and let it rest for a couple minutes?

  9. #9
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    yeah

    i was using the docking station as the original power source and I have it stripped down to just the motherboard. There is power coming out of the docking station, i believe. but even after letting it rest it doesn't start up.

  10. #10
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    One thing to check on the board is a fuse. Most modern laptops have polyfuses (hence the waiting after you do something stupid then trying again)

    but sometimes they still have fuses. It might look like a resistor soldered to the board, when I replaced one once it was green I think.

    Set your multimeter to continuity mode and look at everything that looks 'fuse like' to make sure it conducts. If you find something like this that doesn't conduct, and you're fairly sure it should, you could try shorting it out temporarily to see if you can get the laptop to power up.

    If it does, then you've found your culprit. I resuccerected a Pentium board like this once (blew the keyboard fuse)... I was dodgy and replaced the fuse with a piece of wire... DON'T do this, unless you're sure you'll never do something stupid again

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