Sycmaster 204T works great for 20 seconds then screen blanks

You have bad caps in your monitor

How to fix a blank screen in 60 seconds: Fix Sanei N10 blank screen in 60 seconds

It sounds to me that you have the resolution on the wrong setting. Go a a clear space on your desktop, right click, and select properties. When that opens go to the settings tab and change the screen resolution to 1600 X 1200. This is the native setting for the monitor. If that doesn't fix the problem continue changing the screen resolution until you get one that works.

Best bet is to take it back to where you bought it, and get a replacement.

The power supply-inverter board is probably at fault. Remove the back cover and locate the standard ac power cord connector. The board that the power input connector is soldered to is your power supply - inverter board. Check the electrolytic capacitors on the board. They probably went bad. A visual inspection is usually enough to find out which ones are bad. They will be either bulging or cracked at the top and leaking fluid. I usually replace all of the capacitors that have the same rating whether they look bad or not. Will save you another repair later. If the caps don't look bad, you can take the board to your local tv repair shop and have the caps checked with a esr tester. It's more accurate and they can be tested with the caps in place. Hope this helps.

Hi,
Please check that all the cables are plugged in firmly on the back of the monitor and on the back of the computer.
However....
It sounds like the back light on the screen is faulty. If this is the case it is definitely a return for repair problem. You should be able to find the warrantly procedure for your area on the samsung website.
Cheers
Dave

Try to replace C110 and C111 in the power supply circuit. These are 820uF caps and are in parallel. I had slow start and a flicker on this same monitor. Replacing the caps fixed it. Good luck, Ryan

This is the way how to examine what's wrong with your LCD monitors. After you turned it on and the screen stopped working, you have to check that if you can see the image on the screen or not by shining a flashlight into the screen, not directly but find the best angle to the screen and take a look very closely. If you can see the icons or any image, there will be a minor problem. This is because of the lamps inside screen. Some of them were broken and it is very easy to replace. If you cannot see anything on the screen, there'll be some problems with inverter board. If you have soldering tool and want to fix it by yourself, check the caps first. It may cause this problem. Some caps might show leaking or burn spot on the board because of too high temp. If you don't have soldering tool, you better go get a technician to do so. Hope this help!! If anything I can help you with, feel free to let me know.
Thank you,

i got the same prob.supposedly its the cap(capacitor) ,the one for the power suppy near the cord input.im getting my shit fixxed.and i will let you know.

I fixed my AL2021 by replacing the output caps on the power board. $4 repair. Pull the thing apart and replace the 1000uF, 680uF and 470uF caps on the end of the power board.