Could anyone here help me?

Greetings~
Could anyone here help me? I am a bit of newbie to touch electronics. The circuit which is based on LM2596 is given below,please have a see.

This is a circuit change voltage from 12V to 4V. The P-MOS is the MOFSET of AO340.
I don’t know why it’s useless.
I have measured it. The source electrode–12.26V, grid electrode–11.89V,drain electrode–0.145V.

Was MOS broken? Or LM2596? Is it suitable here? Please help me,thanks!

You know. This is not an electronic forum.
Anyway, check if the resistors are inverted on the actual board: if R203 and R204 are inverted.

12.26V * R203 / (R203 + R204) = ~11.86V (Nice voltmeter, I’d say)
Here we have resistors inverted

12V * R204 / (R203 + R204) = ~0,39V
Here we have the voltage as per schematic: correct resistors order

12V * R204 / (20K + R204) = 4V
Here we have the voltage as per schematic: correct resistors order, but with R203 = 20K

Please, let us know.

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