The complaint for this Samsung SyncMaster 540n monitor was its take a while before the display comes, some times half an hour some times 15 minutes. I have repaired several of these in our shop and they all have the same exact issue with the power supply. If you have a Samsung SyncMaster 540n with the same problem this should help get you back running.
First you need to remove the power cable, signal cable and the stand. To remove the stand you will need to remove the 3 thumbscrews, they are circled in red.
Remove the cover, to remove the cover you will need to use the small flat blade screwdriver. Across the side there are several release tabs, if you insert the screwdriver into the slot, the case will release.
After the plastic cover is removed. You will need to unplug the control panel and the 2 backlight connector, circled in red. The last cable to release is the panel signal cable, circled in blue. After unplug the 3 connector slightly lift up the metal case and unplug the panel signal cable.
To remove the board you need to unscrew the 3 screws circled in red and unplug the signal cable, circled in blue.
Capacitor that need to be replaced are circled in yellow. As you can see in the picture above the caps had very noticeable bulging tops. This caps is the source of the problem, in other cases there 2 or 3 bulging caps so you have to replace them all. Be sure to reinstall the caps with the polarity stripe going the same direction as the old ones come out.
After the replacement of parts. Apply power and you should have a fully functional monitor again.