Question Can I turn the Power supply on with connecting only Fan hub to it ?

My immediate response is no.

Much more needs to be known.

Is there a specific problem with the PSU or build?

= = = =

Update your post to include full system hardware specs and OS information.

And include more details about what is being connected to what?

References, photographs, etc. would help.

Details matter.

PSU: make, model, wattage, age, condition (original to build, new, refurbished used)?

To test PSU:

https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158
 
You merely need to jump a green wire with any black wire on the 24pin connection/harness, it's called a paper clip test but you should know that the test is flawed. Why? You may ask. It's because the test doesn't tell you how much power the PSU can effectively output, all it does is make the fan on the PSU spin up.

Why are you even bothering with testing a PSU? Might want to mention your full system's specs as my colleague above has asked for and if you're investing in a second hand PSU, please rethink that decision.

Moved thread from Cases section to Power Supplies section.
 
My immediate response is no.

Much more needs to be known.

Update your post to include full system hardware specs and OS information.

And more details about what is being connected to what?

References, photographs, etc. would help.

Details matter.
I am Building New PC
So i need to Test PSU and Case fans only before installing The remaining components
PSU ( MSI A650 BN ) and Case ( Xigamtek Cubi with 7 fans on Fan hub work through molex cabel )