have a LCD monitor but when power on, no lights detected, may I ask what’s the problem?

Have you check the output voltages from the smps? If no output then check all the components in the power side. If there are voltages entering to the mainboard then suspect a bad mainboard especially the MCU

Thank you. You are so nice to help this beginner. I am glad to know that the 3.3 VDC to the main board is correct.

No problem!

You say that ”Once the MCU received the 3.3 volt and the vga signal cable is connected then it will send a on signal to the optoisolator circuit to trigger the main power supply. ”

I have found the return path for the signal to the optoisolator (the blue wire) from the main board to the standby power supply. It should turn on the optoisolator for the path then goes to the main power supply to turn it on. I assume the on signal I am looking for is a 3.3 VDC signal here.

Yes it can be that voltage. As long as the signal is more than 0.7 volt it can be used to trigger any circuit that use semiconductor.

What do you mean by vga signal cable? Is it the wire bundle from the Main Board to the Power Supply or is it an external signal cable, as an antenna or computer line that must be connected to the main board for the MCU to work?

Vga signal cable means the Signals coming out from the computer (RGB, H and V signals) and to the lcd monitor motherboard

I wonder if you could answer me this another doubth about a proyection lcd tv the model is KDF-E42A10

The problem with this lcd is that there are vertical lines in all the screen it could be the panel


Vertical lines is usually the fault of panel and it can’t be repaired

I have a question regarding LG Flatron L1810 LCD monitor.
The monitor was completely dead.
I replace few components in the SMTP power supply and it back to work, with good 5V & 12V output.
Now the LCD turn on - green LED in the panel, the CCFL are on, but there is no display even no OSD menu.
Do you have any idea?

Thanks a lot,


It could be the Mainboard MCU problem. I came across few units of Samsung that have the same problem

LCD

I am still trying to fix the Samsung lcd, I found out that I am getting 13 volt out of the power board,there is 10 wires coming off the power board going to the control board board. Soon as I plug the cable into the control board the 13 volts disappears.for some reason the power does not get to the control board .Is there something blocking the power



HI Richard,

It is either the 13 volt line itself have problem (can’t sustain the demand of load-it can be a bad filter cap) or the control board have something shorted that you need to check it out

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LCD

My Fuji Plus 19″ lcd monitor has run its life…, but now all of a sudden it keeps going black. it will just be working or doing something and the screen will just go black, but the green power light will remain on. the only way to get the picture back is to turn off the screen power, then turn it back on after a few seconds and it will come back on for another 2 seconds or so and goes blank.
I unplugged it all and then reattached it but now when it press the power button the monitor will only show a picture for about 2 seconds and then goes blank. The green power light stays on the whole time and if I turn it on and off it will show the screen again for 2 seconds and then go blank.

It could be the problem of bad filter cap (e-caps) at the smps that you need to use ESR meter to check it or one of the backlight already have problem
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I have a background’in computers and I’d like to learn how to repair LCD monitor/TV, but My question is… Is it really worth it?

Once you know how to repair electronics, you will have many choices of repair field you want to choose. It is not necessary have to be in consumer products electronics repair. It is worth it to equipped yourself for your future.

Is it a good business?

It depends on how you run your business.

I need to know because nowadays one can buy an LCD monitor for as low as $100. In the other hand if you ever need to repair one, just the inverter or back light could cost you $150, so where is the logic here.

Most of the time, the backlight, inverter and power supply circuit can be repaired and the cost is very low. You will make some profit if you constantly get lots of Monitor for repair. As mentioned above, it is not necessary have to make money from this field alone.
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QUESTION

having trouble with some psu’s in smaller lcds like the nec 1550v still learning the basics can you give me any tips i have 3 units that do not power on but the power led flashes green somewhat rapidly and then a fourth that works fine but i have compared nearly everything save a few components im not sure i can test with my multimeter.

ANSWER

Is the output voltages from the SMPS good an stable? If yes then suspect a bad MAINBOARD. If no then suspect either the inverter board components shorted that pulled down the SMPS or the SMPS itself has problem

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