I put the power cable in the socket, turn on the TV, flash the power 5x led and here comes the image. I leave it on for a while, I try to turn the TV off by pressing the power key, the TV turns off but when I try to turn the TV on again it doesn't turn on. Ai only turns on after removing the power cord from the outlet and plugging it in, it works. Another symptom that the customer complains about is that when the TV is off for a long time, when turning on the image it becomes a little clear and normalizes after a certain time.
It gives the impression of being a source problem, that when it is cold the TV presents the problem and normalizes after it heats up.

Check the power supply and main board.

I made some measurements and noticed that the first instant I turn the TV on, the voltage on the C9110 electrolytic capacitor that powers the LED bars reaches around 250v. Then I turn off the TV by the power button. When I turn the TV on again, the standby led flashes about 5X and the image does not come, at this moment the voltage over the same capacitor now does not exceed 145V.

Disconnect the cable connecting main and the power supply and turn it on.
If the backlight does not appear, then change the LEDs or repair the power supply.

I took a closer look at the source plate and missed a component on the source plate. This component may be the cause of the TV defect. The missing component is DQ857 (KDS184) in line DRV_OCP1 and DRV_OCP2

I'm thinking that another technician removed this double diode so that the television would at least turn on, now after I put this diode back on, the TV now blinks every 3 seconds without the image appearing or turning on the LEDs

Unplug the power supply from the main board and turn on the TV.
If the backlight appears and all the power supply voltages are normal, then repair or change the main board.

СКАЧАТЬ Samsung bn44-00472a PSLF800A03S схема блока питания : BN44-00472A.pdf
СКАЧАТЬ Samsung+UN40D5003BF : Samsung+UN40D5003BF.pdf
СКАЧАТЬ сервис мануал на английском Samsung UA26D4003BM шасси U61D U61E : сервис мануал на английском Samsung UA26D4003BM шасси U61D U61E.pdf

после установки двойного диода (DQ857) я включил телевизор, светодиод на передней панели мигал 1 раз каждые 2 секунды или около того, изображение не возвращалось (темный экран). Я заметил, что проволочная сетка разъема CNL802 была ослаблена, возможно, именно это вызвало этот признак мигания светодиода панели. При пайке провода и включении телевизора я заметил, что теперь телевизор включается и выключается нормально, но изображение не появляется (экран остается темным).

Unplug the power supply from the main board and turn on the TV.
If the backlight appears and all the power supply voltages are normal, then repair or change the main board.