I use a power supply for nextion work. In the datasheet, the operating voltage is maxed 7V also typical voltage at 5V. but my nextion not working at 5v. My nextion, starts working at 8.5V. It seems to provide maximum efficiency when it comes to about 10V. when I decrease voltage nextion is not closing, just the brightness decrease and the screen is blacking
That 3V3 regulator on the board must be getting hot?
yes, it’s getting hot.
Have you considered measuring the output of the on-board 3V3 regulator with 5V confirmed on the input?
If it’s dropping regulation (ie; < 3V3) it’s obviously out of spec and you can replace the regulator.
They run warm (depends on back lighting level, of course), but they should not be “hot”.