HP800 G1 annoying noise when computer turned off (PSU??)

My computer HP800 G1 SFF produces tiny but annoying squeeking noise when computer is in sleep or even when turned off!

When I turn pull out the electricity plug it's silent. I opened computer and
it seems like it's coming from the direction where the PSU (POWER SUPPLY UNIT) is.
Would PSU be very probable cause for the noise?
Could it originate from some other component or fan in computer too?
Here is my computer's description

Do you have any suggestions for a new more silent and pleasant PSU (and possibly powerful too)?

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Get a can of compressed air and give the psu a good blow out from both directions.

While your in there give the rest of the the pc a blow out.

You might want to take the machine outside to do this as a lot of dust may come out

That psu seems to be a propretary thing so it's back to HP for a new one.

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"My favorite" Canned air has saved me a lot of repair time.

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