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Lcd Monitor Power supply repair

 

 

 

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Troubleshooting tft or lcd monitor switch mode power supply is easier than the crt monitor. It is small and compact and usually have only one output which is 12 vdc from 2 amp to 4 over ampere. Some design of lcd flat panel or flat screen monitor power supply are built into the mainboard while the other are separated as power pack module. The power pack module type is easy to diagnose because you can replace another working unit just to make sure is the power pack that giving problem. Sometimes a shorted component in the main lcd monitor board can cause the power to blink and low power symptom. The best is to swap with a known good unit or using an external dc power supply.

I have a method to show you how to find out if the lcd computer monitor power supply problem or the mainboard. Just connect a car 12 volt rear light bulb to the power pack. If it light brightly the power pack is ok if it blink or dim the power pack have problem. From experience, most of the lcd screen display power supply problem are due to the failure of electrolytic capacitor in the primary and secondary section. Most of the capacitor have a high esr which cause the power supply to produce low output, blink or no power at all. Typical value electrolytic capacitor in the primary side are 47 and 100 micro farad 50 Volt and the secondary side are 1000 to 2200 micro farad 25 volt. Sometimes you can see the capacitor top casing became bulge and the sleeve that covered the capacitor casing turned into darker color.

The power section in some of the lcd screen are still using the UC3842 pwm ic. This type of ic is quite easy to find in the market compare to some power  ic which is very difficult to find such as the TEA4533AP. Another disadvantage of repairing lcd monitor power supply power pack is that the casing sometimes have been totally sealed and you have to carefully open it up otherwise you may easily break the casing.

Lcd repair for monitor or television i believed is quite the same but first you must know the principle. Once you know the principles you will know the rest.