Monitor comes on,then goes off after a couple of seconds.Checked the circuit board but found no problem,feel that the screen might be faulty,please help.

Hi,
This could indicate some component overheating/damaged. I haven't worked on a monitor like yours, but on several occassions I noticed that the problem was caused by blown capacitors. This can usually be spotted if you inspect the capacitors on the logic board carefully. If they are bulging or you can see black goo "leaking" from them then they need replacing. Other than that, troubleshooting of other components on the logic board is far too complicated to describe here.
Hope this helps,
Raf

Borrow a second computer, e.g., a laptop, and a second monitor.

Does the second monitor work, when connected to your computer?
If not, then it's your computer (probably the video-adapter) that is the problem.

Does your monitor work when connected to the second computer?
If not, then it's your monitor that is the problem.