LCD screen backlight off

Q: The backlight on my LCD screen (laptop, TV, computer monitor, etc) is not working. Can I fix it myself cheaper than it would cost me to have it done by someone else?

A: If you like and are able to fix things yourself, then you can save lots of money by fixing the backlight yourself. I have done it recently on a 19" Dell LCD TV/computer monitor. If you have positively determined that it is the backlight (screen is black but everything else is working), the easy but somewhat costly option is to replace the whole backlight board (if it comes as a separate board). However, if you can solder, you can visually inspect the backlight board. If there are no visible signs of electronic failure, the next step is to check the surface-mount (SMD) fuses on the board (it might help that fuses should be marked as F on the board legend). The backlight board outputs hight voltage, so be very careful. Unplug the power supply from the TV/monitor completely and wait a few minutes for all high voltage capacitors to discharge. Unplug all wires from the backlight board. Find the SMD fuses and use your meter's continuity feature to check them. Also, I tested the fuses by soldering wires to (physically) bigger fuses of the same current rating, and making the backlight to work. Then, I ordered replacement SMD fuses from an electronics distributor, and soldered them in instead of the old fuses, and make the backlight to work. Several tips:

1) It will be hard to find the actual current rating of the old SMD fuses. I did not have a schematic or part number, so I guessed that the backlight will use about 75% of the current that the whole TV/monitor uses.

2) To find the exact replacement SMD part, you will also need to know the case specification. I used a caliper to measure the old SMD fuses, and then looked up the package size on Wikipedia. I then used Digi-Key's filtering utility to look for SMD fuses with that package specification, approximate current rating and the like.

3) Below are the pictures if the particular board that I worked with. The fuses are clearly visible near the center white connector. They are also labeled F1 and F2:



˅˅˅ Additional valuable information is available at one of the links below: ˅˅˅

 

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Page last modified 19-Feb-17 18:52:14 EST
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