Troubleshoot and repair a defective LCD monitor

in repair by DP | 6 comments

Victor took apart a defective LCD monitor and repaired it. The LCD didn’t respond at all to the power button, so chances were good something was off in the power supply. Sure enough there was a bulging cap, replacing it revived the monitor and saved it from the landfill.

Some time ago I was donated a non-working LG L194WT-SF LCD monitor for parts. After a couple of months of collecting dust with it I decided to have a look at it from the inside. Since the monitor has been at a repair shop and was declared beyond repair, I thought I had nothing to lose- best case scenario, I fix the monitor and can use it or give it away in the future, the worst case scenario, I see what components are inside in such a piece of hardware and I might be able to salvage some parts for my projects.

Via Hacked Gadgets.

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Comments

  1. hak8or says:

    Chances are that if the Cap was smaller but as the same capacitance and higher voltage, it has a much higher ESR, in which case it might not work even after changing the cap to a working one.

    Also, hey! Sometimes the LCD’s die out not because of something easy to fix like a dead cap, but instead of a higher failure, like a blown resistor pulling other components with it in my case, a transformer’s insulation breaking down, the PWM ic for the CCFL’s burning out, or sometimes, though very rarely, the logic board going bad. It isn’t always easy! :(

  2. Drone says:

    The title of this post should have the by-line, “Bad Chinese Parts Again!”.

    • Jan says:

      It’s not that the parts are bad, it’s usually poorly designed with the cheapest components in such way, that it will fail soon after the warranty ends. Using caps with poor specs (short life, low capacity, high ESR, low temp rating, etc.) in power supplies is prime example of this. As always, people get what they pay for.

      • hak8or says:

        It is not always a design flaw like capacitors having too low of a voltage rating for their intended application or the application is too demanding for them (too high ripple currents for example).
        I am surprised no one mentioned the “incident” as one of the reason for electrolytic capacitor failures. It is suggested that there was a company thing going on like one company stole from a competing company an incomplete chemical formula for the electrolytic in electrolytic capacitors. Even though the formula was not complete, the other companies stuck with it because it was cheaper than starting from scratch. So, the other companies tried to fill in the gaps resulting in a flawed electrolytic compound that had a higher tendency to fail. The problem with this was that these were major companies, and they produced a huge percentage of electrolytic capacitors. The reason this was not stopped earlier was because no one noticed, the capacitors failed after a while of use. When people did notice that nearly all electrolytic capacitors in their products started to fail, it was too late. Millions of these capacitors with faulty electrolytic were produced, and were included in a vast amount of electronics. It was too expensive to recall all of them and switch the caps, so they left it as is, besides, if the products failed them they would need to buy more electronics.

        Still today we see the effects of this. Old electronics failed due to this problem can be fixed quickly and cheaply by hobbyists. What do you think happened to all the faulty caps that were not already put into products? They were bought off or reclaimed by shady businesses like assemblers and suppliers. Identifying these caps before they failed is not easy or cheap, so chances are that you may have, without realizing, bought some of these failed caps, and put them in your projects. Heck, when companies like Toshiba or Samsung get their parts sourced, chances are that a reasonable amount of those caps are from those times, a ticking time bomb waiting to go poof at some disfortunate consumer.

        So yeah, that is sometimes why electrolytic capacitors fail. Sorry for the long response, I was testing out the keyboard on my touchpad, and needless to say, the findings are not awesome. My thumbs hurt :-(

  3. stephen says:

    Eurostar monitor com tv. modle ES201MTV is power suplly indication available but manualy and remote not come to on mode. need circuit diagrame.

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