How to adjust brightness for samsung syncmaster SA10 monitor ?

I will admit, have never seen you monitor before. But looked up in Google and found this. Hope this helps.

1 Press and hold the power button for 5 seconds. Then a menu should appear...
2 Press and hold it until it is over AUTO. Then tap the button once.

Let us know if it helps. It would not break your monitor to do the above. But be patient and follow the above simple procedures. This could help others same as you.

press d only botton untill menu pop ups than press d only button it switches to other option when it is on auto leave the button and press it quickli again untill its auto start u done !

From the samsung Answer in "How to adjust the brightness on your LED Monitor", There is written on the LIMITATION
Limitations:
This menu is not available when Samsung Magic Bright is set to Dynamic Contrast.
This menu is not available when Eco Saving Plus is set.
This menu is not available when Eye Saver Mode is enabled.
So with those condition matched, This menu(menu for adjustment) will not be available.

UPDATE WITH SOLUTION:
For windows user samsung is only giving link up to windows 7. For windows 8,10 use magicTune lite instead of magicTune premium.

Link for magicTune lite:
http://www.techplusme.com/software/download-samsung-magictune-widnows-8-1

UPDATED 2021-05-06
Above link is not working so adding new working link
https://magictunelitemain.software.informer.com/1.0/

The Blue and Red drives are missing and the TV needs attention by a qualified service technician.

If your trying to get out from the brightness option. Please follow this steps...
Go and click this manual, then at the left side of the manual look option that says for "Adjusting your monitor" then look for user controls.
I hope it helps you a lot :)

Follow these instructions :

1. Turn on your Samsung monitor (if it isn't already.)
   

2. Press the "AUTO" button on your Samsung monitor. This will run the automatic configuration utility. This will look at your current computer settings and adjust your monitor to best match those. This will take a few seconds. If this has calibrated the monitor to meet your needs, you are finished with the process. If it hasn't, continue to Step 3.
3. Press the "Menu" button on your Samsung computer monitor.
4. Use the arrows and the "Enter" button on the monitor to highlight and select various settings categories.
5. Use the "Brightness" menu on your Samsung monitor to adjust how bright or dark you want the image.
6. Use the "Colors" menu to adjust how prominent certain colors are displayed on your Samsung monitor.
7. Use the "Contrast" menu to adjust the level of black on your Samsung monitor.
8. Select "Save and Exit" to save your changes and exit the Samsung monitor's on Screen menu.

It has Brightness, Contrast, Color adjustments. Here is the user manual:
http://www.retrevo.com/support/Samsung-245BW-Monitors-manual/id/2994ag901/t/2/

Is the auto adjust button stuck?

Your logic board need to service.