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Screen replacement headache...

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  • Screen replacement headache...

    I've been trying to fix a laptop (Lenovo R400) for somebody for a few weeks now. It was brought to me as "dead", but in fact turned out to be working fine except there was no output to the laptop's main screen (plugging another monitor in shows everything else is working normally).

    "Should be an easy fix" you're probably thinking, I know I was at first.

    Took it apart to clean it and check all the connections. This is when I spotted something had melted on the motherboard:

    (yes I'm still working on that one I mentioned in the ebay thread weeks ago)

    So I replaced the motherboard. Problem persisted... Then I thought maybe the inverter had died as well? So I replaced that next hoping for a cheap, easy fix. Still doesn't work...

    On closer inspection of the screen with a super bright LED torch I noticed a small crack at the top of the original panel near where everything connects to the back of it... At this point I'm still thinking it's going to be an easy fix... I've replaced a fair few laptop screens in the past, and already have quite a bit of experience with Lenovo systems in particular...

    Now I've replaced the actual panel (with a compatible one the second time around I might add, as the first one I ordered was CCFL instead of LED - whoops) Fixed? Nope... The fan spins, the back light comes on for a few seconds, but still nothing showing on the main screen.

    It's also sometimes randomly shuts down after a few seconds now, I thought that might be battery related but it even happens on charge... Doesn't always do it though. I've stripped everything out looking for any loose screws or anything else that could cause a short... Nada.

    So I've currently got the new motherboard that doesn't have any visible damage (but is 2nd hand off ebay), with the original CPU, one of the original sticks of RAM, the keyboard and the laptop screen plugged in...

    I'm assuming the keyboard supports, touchpad, wireless card, dvd and hdd aren't an integral part of the display (they're currently scattered around my worktop). I should at least be able to get the post/bios up

    What am I missing?

    1. LCD connector cable? Cheap/easy fix, but I've never seen one stop working without showing visible signs of damage... Also with damage to other components being found/fixed I kind of figured the cable would just still work?

    2. Is the "compatible" monitor not actually compatible? It was listed as a fully compatible part, and has all the right connections, though knowing what laptop screens can be like I wouldn't be surprised to find that this was for a slightly different version or something stupid.

    3. Pepsi? Nope. It's not dead. It's been sat on a shelf for a couple of weeks while I've been sourcing parts, but I'm confident I can hook my monitor up to it and still be able to get in to the OS - after I've plugged the hdd back in obviously).

    4. Power issue. The battery is old and tired, and could do with replacing. It only holds it's charge for a few hours when not in use, and about 45 minutes to an hour in use. The melted chip on the original motherboard was a fuse (you can see it is labelled LF10A in the picture above - "Little Fuse 10Amp"), so a power surge could have fried something. Surely though replacing the motherboard for one where that fuse is intact shouldn't yield identical symptoms, and a tired battery shouldn't stop the main screen from working when it's on charge should it?

    5. CPU/GPU. Is it even possible that either can be damaged in such a way that they just can't send info to the main screen but function perfectly normally otherwise? If it's the GPU then it's both of them (one on each mobo), but CPU I can swap over...
    Last edited by FunkY; 17-04-15, 15:56.
    Why did the chicken cross the road?
    To get away from the Canadian poultry farmer with loose trousers.