SKR2 - Board won't start with 24v but starts with USB

[Landif]

I brought a new SKR2 rev B with 5x tmc2226.
I connected the board directly via USB and configured, installed new firmware, etc... After that, I replaced my old board with this SRK2 but the board refuses to start on direct power mode (24V). I even replaced the two 10A fuses with brand new ones in the hope that was a simple fuse issue but no luck...
The board continues to start normally with a USB connection and jumper set to USB power but the TMCs won't start that way...
This is a hardware failure or am I missing something?

I created a vídeo showing the board's behavior.

Thanks

Edited April 26, 2022 by Landif
added board name to the title

[BTT Tony]

Hi ，
Thanks for your information.

Please test the continuity of the fuse at the motherboard

[Landif]

All fuses have been tested and they are good.

With Github's community, I have done some debugging and there is something wrong with the board.

You can follow the full discussion here:
https://github.com/bigtreetech/SKR-2/issues/144

 

[BTT Tony]

Hi ，
Apologize  for the late reply.

The terminal of the power port itself has a part of the resistance, it will divide a part of the voltage.

Please check the 3.3v,5v mosfet with the multimeter .if as the picture. 

Does the motherbaord update the firmware successfully?

Does the display work fine with skr 2 motherboard?

 

[Landif]

I measured voltages on the MOSFET:

In vdd mode (jumper top + mid):
5v mosfet = no power
3.3v mosfet = no power

In USB mode (jumper mid + botton) and USB connected:
5v mosfet = 5v
3.3v mosfet = 3.3v

In USB mode the board boots, the board lights on and I can flash firmware normally. I don't use display, so I don't know if it works. I can flash Klipper, in USB mode, and access the board normally. Then, in VDD mode, the board won't start. I flashed Marlin from the official repo to test but the board still with no power in VDD mode.

Note: I successfully measured 12v between DCIN pins and both sides of the fuses nearby.

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