but a close look at the LCD shows a very faint white light on the screen and the power LED does not glow. The cover was a little easier to remove than other models. As usual, whenever the motherboard and power board are exposed, there are bald capacitors, dark areas, loose connectors, etc. I would call. But these display panels looked perfect. The next step was to separate the power board / inverter from the mainboard. The energy was on the power plate and I could hear a soft “soft” sound. When I measured a 12-volt line with the best multimeter, the drop was around 7-8 volts, which is very unusual. Actually, this is good news for us because we know what to do next.
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Now we can use a 12V auto brake light bulb to test
the part causing the low voltage output problem. If the LCD is designed to operate on 18 or 24 volts, you can use a light bulb from a larger trailer. A faulty element on the primary or secondary side can cause the output voltage to drop. Removing the fuse as shown in the picture and connecting the lamp between the supply line and cold ground can find out which part is causing the problem. You can use this method, but you should verify that the secondary filter capacitors, TL431 adjustable microswitch regulator, optical dielectric, and components surrounding the optical isolator are working before using the bulb. Do you work
When the bulb is turned on, it still does not light up and the sound can still be heard. This indicates that the primary side has a problem and we can leave the inverter / high voltage area and focus on finding faults in the primary section.
It’s really time to test your basic electronics skills because now you know where the wrong is and you need to use your skills to find exactly bad content. There wasn’t a lot of stuff on the primary side and you can easily check them all in less than 20 minutes. After checking all the ingredients, I was surprised that they were all tested properly. The switching mode will cycle the primary direction of the converter 8 times, indicating that this is fine, and the uc3842b PWM Power IC will not work even when powered! Solving such a problem was a huge challenge because I was 100% sure the cause of the problem was the first party but still you could not find the culprit.
Since I have checked all the components and cannot pinpoint the fault,
all I can do is replace semiconductor devices such as diodes, SRR, Fairy, and transistors. Below full operating voltage when I experienced a semiconductor component failure. I changed the semiconductor components one by one and changed it every time I changed it to see if the power bulb was on. Guess what, you won’t believe I just lost it – the poor quality 2N7000! The moment I switch this fetus and energy, the lamp lights up instantly. I couldn’t believe it was the embryonic error that caused all output voltages to drop! I am so glad I finally fixed this problem and who knows, this could be a common bug for Dell’s E151Fpb LCD Monitor. So please note all LCD repairs.
I started retesting the wrong bowl 2N7000 with my analog meter and peak electronic atlas component analyzer, the result is still the same as I tested it fine! Like the return transformer, the best test equipment to test oil and other components, at full working voltage, frequency, signal, etc. What I learned from here is whether all questionable ingredients are well tested. The only way to reveal the truth is by directly replacing parts. We hope you enjoy this article and more! I wish you the best repairs!
