Wednesday, February 18, 2009

Fixing LCD Monitor

Few weeks ago, my sister-in-law asked me to fix her LCD monitor, which became dark, very dark when turned on. It's a 19" Westinghouse model L1975NW. I took the back off, and notice the board has few components which responsible to drive the back-light of an LCD screen. After tracing out the circuit, and identify failed components (a surface mounted fuse) I went ahead order parts at Mouser Electronics. Even though only the fuse is definitely failed, I also order new FET & capacitor, just because I have no way to test them. While waiting for the parts to arrive, I removed the FET, capacitor & the surface mounted fuse. Few days later the parts arrived, I soldered them on the board and very happy that the monitor is now fixed. If there are anyone interested, I'll post the part lists & locations of them on the board.

Here is the picture of the power board, with the FETs circled. Unfortunately, I did not take the picture of the other side, where the surface-mounted fuse resided. After removed these components & replaced with new ones, the monitor works again. BTW, when I order the FETs, I also ordered the clip on heat-sinks for them, I believe that these FETs were driven so hard & so with the heat sinks they will certainly help prolong the life of the new FETs.

Here are the list of parts that I ordered:
  1. Qty of 2, FETs
  2. Qty of 2, TO-220 heat sinks
  3. Qty of 1, fuse
Removal of the FETs was not that bad, but soldering the surface mounted fuse was a bit difficult. My eyes aren't as good as they used to be, so I need a magnify glass to perform this task.

Also, correction: I also ordered the capacitors, however I did not replace them, for I believed replacing the FETs & fuse would be sufficed, and indeed they do. So, after replaced the FETs & fuse, I put them back together and the monitor is revived.

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