Why is the blacklight not working after screen replacement?

I have a Toshiba R950 with a faulty LED blacklight. The screen is very dark and you can see text when you use a strong light. So it is a blacklight problem. I have ordered a screen from china, with a higher resolution, but same 40 pin and almost the same screen model number. The blacklight was working, but the screen was green and blurry. I swapped the china screen with the old one, the old one has still no blacklight. After swapping once again, the china screen also has no blacklight anymore! I have ordered the same screen as the original from the Netherlands, but it has also no blacklight. So I have 3 screens with no blacklight. What can be the problem? I think it is maybe the invertor, but that is mounted on the screen, so I don't know.

Thank you in advance.

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@kevinb1012 it is possible that the screen with the " almost the same screen model number" has shorted out your backlight circuitry. Since it is an LED backlight there is no separate inverter. The driver and converter for the LED's are all part of the motherboard. You would need a schematic and layout for your specific motherboard. Take a good look at all the components on your board and see if you notice any obvious damage. Sometimes it helps if you post some images of both sides of the board with your question. Use this guide Adding images to an existing question for that. Even within the same model you may have variations on the motherboard. You need to identify that first. Bigger issue here is that you are dealing with a Toshiba. That company is as paranoid and secretive as Apple, maybe even more. Finding any schematic etc. is almost impossible.

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THe problem was the fuse on the motherboard. There were about 5 fuses on the motherboard, after testing with a multimeter, I concluded one was broken. I puta small wire above it, because these fuses are very difficult to get. The original screen is now working too! That's strange, because how can a fuse by itself get broken. But anyways it is working now. Thank you for your help.

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@kevinb1012 "possible that the screen with the " almost the same screen model number" has shorted out your backlight circuitry. " most likely the reason why "how can a fuse by itself get broken." Great that you got it fixed and best of luck to you!

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