Ladislav Lencses, use [https://www.ifixit.com/Device/Samsung_SyncMaster_205BW|this guide] to disassemble your display. Then check the capacitors on the power board. Check for any leakage, bulging etc and see what you find. Capacitors can of course fail without any visual indication as well. So, unless you have a tool like a capacitance meter, you may want to consider to replace the capacitors by using a complete kit [http://www.amazon.com/Repair-Samsung-Monitor-Capacitors-Entire/dp/B0053DAP3Q|like this one.] Hope this helps, good luck.