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Thread: Thinkpad 755C with dead backlight: Worth replacing? Possible to replace?

  1. #1
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    Default Thinkpad 755C with dead backlight: Worth replacing? Possible to replace?

    I got a pile of 486s from a coworker earlier: Two AT&T Globalysts and a Thinkpad 755C. The former two didn't have any clearing issues, a dead HDD on one globalyst aside, but the Thinkpad's got a dead LCD backlight. Is addressing that a fool's errand or is it worth a shot? Are there any common part numbers i should be on the look out for?
    General Failure Reading Drive C -
    Abort, Retry, Ignore?

  2. #2
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    Principality of Xeon W-2140B the Great State of Central New Jerky
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    I can't remember exactly which model, and it may actually be the 755c, but I have nos complete lcd assemblies. Case plastics and all. 25$ + shipping if interested. I sold 2 or 3 a while back to a very happy customer. I'll look up the relevant model/s.

    Whoops I think these are specific to the 700c. Apologies.

  3. #3
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    Anyone know where the inverter board is? The pertinent IBM Mobile Systems HMM doesn't say a lot on that note.

    EDIT: Inverter's part of the LCD assembly. This bodes well for my hopes that a panel swap will suffice.
    Last edited by MrArgent; May 20th, 2020 at 06:05 PM.
    General Failure Reading Drive C -
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  4. #4

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    Replacing backlights are worth it, They run about 20.00 shipped from ccfl warehouse. If you can't find your model screen, you can email them your specs off your current ccfl and they'll build you one.

  5. #5
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    Some early LCD's can be a PITA to open and replace the backlight. More likely with a dark LCD is a dead inverter and repairing one can be easy of it's just a fuse or a transistor. Check voltage coming to the inverter too, it could be a wiring problem or a fuse on the motherboard. Also, look for the lid closed switch and make sure it is not stuck or defective.
    Crazy old guy with a basement full of Pentium 1 laptops and parts

  6. #6
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    Quote Originally Posted by DeltaDon View Post
    Some early LCD's can be a PITA to open and replace the backlight. More likely with a dark LCD is a dead inverter and repairing one can be easy of it's just a fuse or a transistor. Check voltage coming to the inverter too, it could be a wiring problem or a fuse on the motherboard. Also, look for the lid closed switch and make sure it is not stuck or defective.
    Yeah, the 700C and 755C seem to use the same backlight/inverter board so I'm hoping one of TiPC's spares can help me here.
    General Failure Reading Drive C -
    Abort, Retry, Ignore?

  7. #7
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    If it is a true dark LCD due to inverter/back light problems you should be able to see a VERY dim image on the LCD. An bright light held at an angle to the LCD should somewhat light up some of the image and let you know the LCD and computer are both working and you need to fix or power up the back light. Always remove the main battery when playing around with the LCD wiring since sometimes you can damage the circuits if the battery is installed when connecting or disconnecting the LCD cables.

    Hang onto the old inverter is a new one solves the problem - many good parts on it and they are becoming hard to find these days. Could come in handy in the future.
    Crazy old guy with a basement full of Pentium 1 laptops and parts

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