Hi ekrokosz,
If you're unit has a start-up problem, then this is an indication of out-of-regulation in the power supply board. This is caused by leaky/dried electrolytic capacitor in that board. In the first stage of the symptoms, warm-up will make itself stable but it will get worst, time will come that the unit will not power up at all.
Leaky electrolytic capacitor has bulged/dome at the top and can be easily identify by visual inspection. See sample picture below.
Faulty electrolytic capacitor with dome at the top.
Dried electrolytic capacitor has no physical indication of fault. You must have a capacitor checker to determine its condition.
If you don't have necessary tools and test instrument and can't troubleshoot the unit yourself, I would advice you to replace the entire power supply board, this is more convenient because no soldering required. Obtain it from your local Samsung service center or online.
Hope I helped you.
Have a nice day!
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