Flickering and NOT flickering on same LED strip

[StefDrums]

dear @blazoncek thanks for your reply.
Ill try to answer as well as I can to all your questions:

@blazoncek

You are not showing what your PSUs look like.

I have 2 PCB with 2 different PSU:

• DevKit is connected to my USB 3.0 PC port
• custom PCB has a 4,6V 5A DC/DC converter

@blazoncek

If you have proper PSU with enough A to power your strip and ESP connect that, not 4.6V but full 5V or even 5.1V.

Yes, I’m sure that both of ther can power up 3 WS2813 LEDs.
When I power up all the 45 LEDs, the works well, except the first that is flickering.
The issue is the same with 5,0V supply and 4,6V supply. Both board have ESP32 powered at 3,3V.
WS2813 works from 3,7V to 5,5V so a 4,6V level for power supply is not critical (and also there is the same issue with 5,0V supply from USB)

@blazoncek

Then use recommended level shifter

SN74LVC2T45 level shifter is one suggested by WLED faq (and also its signal is clear, by the way I checked it with my scope, its a clear plot).

@blazoncek

and if LEDs still flicker disconnect all peripherals from the board and use only ESP, level shifter and LEDs.

already done: with 3 LEDs both works, with 45 LEDs the first LED is flickering

@blazoncek

If it still flickers it may be faulty ESP or faulty LED strip.

I think that it’s rare that 2 different ESP32 could be broken in the same way.
About the LED strip: 3 and 45 came from the same reel. I cutted the 45 removing the 1st LED, now it has 44 and has the same behaviour.

Thanks in advance for your reply, I hope to find the solution!

EDIT:
I also attach a picture of my power supply: from 4,6V up to 5,1V same issue

video: WLED solid orange 45 LEDs strip 5V1 power supply