E151fpb Dell LCD monitor came with the complaint, no power, but on careful attention to the LCD display shows could see a very slight (Blur) white flashes across the screen and the operating LED is not lit. Remove the cover was a bit easy compared with other models. As usual, when the main board and board would be exposed, I would look for any bulged capacitor, darkened room to solve a plug and display boards, etc. But this looks perfectly fine. The next step was to the individualPower / inverter board with the motherboard. Power was applied to the board and I could hear a soft "Chip Chip". If I do 12 volts using a digital multimeter, the reading was about 7 to 8 volts, which was very unusual. In fact, this is good news for us because we see what is the next step that we should know.
Now we found a significant cause 12 volt car brake light bulb for testing on the section of the low-output problem. When running, the LCD monitor designed toat 18 or 24 volts then you could use a light bulb from the big trailer. A faulty component in the primary or secondary side can lead to low output voltage. Remove the backup, as shown in the picture, and connect the lamp between the inlet and the cold ground could tell which section is giving problem. You can use this method, but first you must confirm that the secondary filter capacitor, TL431 adjustable precision shunt regulator ic, MOSFET and components around theOptocoupler is working before you are done with the light bulb use.
When the device is switched on the light bulb still does not light up and hear the sound too. This suggests that the primary problem with the page and we can leave the inverter / voltage range and concentrate to find the errors in the primary section.
This is the time to really test your skill fundamentals of electronics, because you now know what area the fault is, and you only need to use your skills to find thoseexact faulty component. There was not much components in the primary side, and you can easily check, all in less than 20 minutes. After checking all components, I was surprised that all of them tested okay. Primary winding of switching power supplies transformer rings 8 bars, which indicates good and also the uc3842b PWM IC replaces the power will not work yet! It was quite a challenge to resolve this kind of problem where you are hundred percent sure that is the primary siteproblem could not give out the perpetrators.
Since I had checked all the components and could not find the error, the only way that I can do is to replace direct the semiconductor components like diodes, scr, fet, and transistors. Of semiconductor components, I experienced a breakdown on when under full operating voltage. One after another of the semiconductor components, and I replaced the power every time I had changed it to see if the lamp is lit or not. GuessWhat, you would not believe what I just discovered a defective 2N7000 fet! The moments I have fet them and turn the lamp immediately lights replaced. I could not believe that this faulty fet that all causes output to fall! I was so happy that I finally solved the problem and who knows, this could note a common mistake for all E151Fpb Dell LCD monitor, please for all LCD monitor workshop.
I began the defective 2N7000 fet check with my analogueMeter and Peak electronic atlas analyzer and the result is still the same good good! Just like flyback transformer to be tested, the best testing equipment and other components FET actually the device itself, because it runs on full operating voltage, frequency, signal, and etc. What you have just learned from here was that, if all the components well suspect tested to replace the only way to reveal the truth, just the parts. Hope you enjoy this article and more good itemscome every day! I wish you all the best and look forward repair!
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