Hello, I am Pete, and I'll be happy to assist with your question today.
It unlikely that the upgrade to Mac OS 10.9 caused the monitor to stop working - it is more likely to have been a coincidence. You can try testing the monitor on a different computer to confirm this.
You could also try disconnecting the screen and turning it on and then try accessing the on-screen menu - you should still be able to see the on-screen menu if the monitor is working correctly.
I did what you suggest. It didn't work. I know the monitor works. It works great on the previous version 10.8.5 (Mountain Lion).
If you did what I suggested and you were unable to access the on-screen menu, then this confirms that the monitor is faulty and the problem is not related to the Mac OS software upgrade.
You can further prove that the monitor is faulty by trying it on another computer with a different OS installed and you will also find that the monitor still does not work.
These old Samsung Syncmaster monitors tend to give up after a couple of years of use due to the cheap parts that were used in manufacturing them, which tend to be unreliable and fail over a relatively short period of time.