How to fix lcd monitors with psu problems?

Gabriel barrandeguy, this is a very broad question and most certainly will be difficult to answer. Always remember that any LCD monitor in general has all the same parts. You have your power supply, most of those having the inverter circuitry on the same board, your video board, your LCD panel and your button bars. Then there are those that have a few other things, like speakers, additional USB ports etc. Most common issues that I found, are power supply issues, with capacitor failure being the number one issue. Bad capacitors are most of the time visually identified by a domed top, or even leaking capacitor. As a rule of thumb, I always change all the capacitors. [http://Check here] for a more visual guide. I believe that Samsung has the greatest rate of failure on the power supply. Most monitors do a self test and have the power light blink a certain error code. This will be monitor specific. As a rule of thumb for myself, I found that if the power light is on, and it does not flash in a specific pattern, and the monitor does not have a clearly visible picture, the error is most likely a bad backlight. All the monitors I've worked on have the backlight circuitry on the power supply board. I have only had very few monitors with failed CCFL in the LCD itself. There are many ways of testing a monitor to determine what has failed. To properly troubleshoot a monitor, I try to get the service manual as well as the datasheet for the display panel. A working knowledge of test equipment like, at minimum a multimeter is necessary. I now use a backlight tester, a multimeter and a transistor tester for the MOSFET on a PSU.