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A Few Tips To Follow Before Repairing Samsung Lcd Monitor
One of the common problems with the Samsung 153v LCD is the display blur. If you approach the screen and observe the monitor in a dark environment, you can actually see the monitor, but it is dim. If you press the front panel button, the on-screen display (OSD) will appear, which proves that the motherboard, driver board, and LCD panel are working. The problem is with the inverter board. The function of the inverter board is to generate an alternating current through the DC voltage to drive the lights on the top and bottom of the LCD. If there is a problem with the inverter board, it will not light the lamp and only the blurred display will be visible.
I still remember that when I first encountered such a problem a long time ago, I could not solve this problem because of lack of information. I did call my maintenance friend to ask for a solution, but no one could give me an answer. Even if you browse "Samsung 153V LCD Blur Monitor Fix" on the Internet, you won't find it. For this reason, I must do my own research to find the answer. I never give up. Winston Churchill once said "Forever, never, never give up." I only post solutions to my loyal members or subscribers - thanks for your support.
Let's start now! Once the lid and the inner aluminum shell were opened, I saw two raised filter capacitors on the secondary side of the switching power supply. Values are 470 and 1000 microfarads at 25 volts. I saw that the other four electrolytic capacitors on the inverter board had changed color, which is a value of 47 microfarads and 25 volts. Using the ESR meter to view the entire board, another capacitor fault (220 uf, 25 volts) was found, close to the fuse (3 amp). Since this capacitor is on the same line as the fuse, I guess the fuse may also give way. Really, checking the fuse with an ohmmeter shows that it has an open circuit.
Now, the real problem that many electronic maintenance personnel deal with with this model is that after replacing all of the above components, the LCD monitor still won't work - still dim! First of all, you must ask yourself why the fuse blows? May be due to a defective capacitor or a short circuit in the fuse circuit? The closest circuit to the fuse is a startup circuit consisting of a pair of NPN and PNP digital transistors (4k7 + 4k7 resistors built into the transistors). Some other designs of LCDs use a combination of C945 and A733 in the startup circuit. By the way, the part numbers of the Samsung 153V startup circuit transistor are A6J (PNP digital transistor) and A8J (NPN digital transistor) as shown in the figure.
Sometimes only these transistors have the problem of causing the fuse to blow (short circuit), but in the above case, both digital transistors can be tested normally. Since both transistors are active, the concentration must now be in the four ICs driving the high voltage transformer because 12 volts is supplied to each of these ICs. There are many part numbers for these four ics, and the most common one used by manufacturers is 4532m. Some boards use the AD4E10 and BBD3N13 part numbers. It is currently difficult to obtain a data sheet or technical specification for this number from a web search.
Do you know what these ICs are inside? It is actually a pair of P-channel and N-channel MOSFETs built in. Do you know it can be tested with meters? Yes, if you use the Peak Atlas component analyzer, it will prompt you for the result. The result is an N-channel FET located at pin 1 (source), pin 2 (gate), and pins 7 and 8 (drain and two pins are internally connected together). For P-channel FETs, pin 3 (source), pin 4 (gate) and pins 5 and 6 (drain and two pins are internally connected). From the above test, I found that two of them are short-circuited. Replace the two short-circuited ICs with capacitors and fuses to restore the LCD display!
There is one more thing I want to share with this model. The inverter PWM IC BIT1305 is very powerful and has few problems.
For more details, visit http://www.ukwiderepair.co.uk
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