Apple Thunderbolt display backlight issue

Hi everyone! I have Apple Thunderbolt 27 display. 2 months ago powercharging stopped working and display began to dim backlight randomly (to appx 30-40%) in 10-30 min after switching on. Reconnecting AC helps, but in 10-20 mins it going to dim again. Last week it has dimmed to ~1% and began to flicker. Reconnecting thunderbolt and AC not helps, it still flicker (i think with ~10-20Hz) with 1% lightness.

I checked 24.5V - it's in normal range (24.8 - 25.05V). USB, camera, sound still working properly. Picture has no visual issues and artefacts (as much as possible to see with 10Hz and 1% lightness backlight).