A LCD monitor was brought to my shop with the problem of blinking stand by LED. It has an external power supply that the customer was not sure if the problem was from the external power supply or the LCD Monitor itself.
I plugged the external power supply to the electrical outlet and measured it with the multi meter and I got 12 volts reading. From experience, I know sometimes, the external power supply will give you the right reading but once you connect it to a load, the 12 volts will disappear.
There is one way to make sure that the external power supply can handle a heavy load. I got a 24 volt light bulb and connected directly to the outlet of the power supply and sure enough, the light was bright and stayed bright for a long time indicating that the external power supply is working fine. This is also an indication that the actual fault is in the LCD screen. So, let the repair begin.
Upon opening the LCD screen I could see a lot of bulged capacitors all across the PC board. I found five capacitors 470uf/25uf volts, four capacitors 220uf/35 volts and two capacitors 10uf/25 volts. That is a total of 11 capacitors in one LCD screen. In my mind, I thought that was an easy fix but in reality, I faced some problem taking the capacitors off the board due to a protective material on the face of the board.
I used a conformal Coating Remover to clean the area and it worked nicely. It took me about 20 minutes to take all the capacitors off and replace them with others. I also made sure that the other capacitors are ok by testing them with the ESR meter and all of them checked ok.
I put the screen back together and plugged the external power in and what a joy it was when I saw a nice picture comes on the screen. Of course, I hooked it up to my laptop and it worked nicely for more than two hours.