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

[Tomas Talaat]

Can i test the PSU by connecting it ( through molex cabel ) to Fan hub only without connecting the Motherboard or NOT ?

 

[Ralston18]

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

 

[Lutfij]

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.

 

[Tomas Talaat]

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 )

 

[Misgar]

Can i test the PSU by connecting it ( through molex cabel ) to Fan hub only without connecting the Motherboard or NOT ?

Back in the 20th Century, I used to connect a significant load to desktop PC power supplies, e.g. 12V 60W headlight bulbs, on the 12V, 5V and 3.3V rails. These days, I just connect the ATX PSU to an old (sacrificial) motherboard if I have any doubts.

I bought a cheap digital "tester" which plugs into the 24-way PSU lead and gives a digital readout of the voltages on all the rails, but I've only used in on some old second-hand Corsair 850W PSUs gifted to me.

I suspect it's OK to "test" a modern ATX PSU with a fan hub, but I wouldn't recommend it, especially if the fan hub is nothing more than a splitter. At the very least, connect 2 or 3 fans to the hub to provide a small load. On it's own, without any fans connected, a fan hub is unlikely to consume more than a few tens of mA, or a few 100mA if it has a digital display.

Alternatively, connect a 3.5in hard disk to load both the +12V and +5V rails. Even here, most hard disks consume less than 8W of power when idle, so it's not taxing the PSU to any degree.

With a brand new, good quality PSU, I just connect it to the new motherboard and switch on. My 7950X and many earlier builds survived this procedure unscathed.

This article dating back 8 years describes some of the reasons why old switched mode PSUs might not be happy when powered up with zero load. This probably refers to AT PSUs manufacturered in the 1990s and early 2000s.

https://electronics.stackexchange.c...g-a-switched-mode-power-supply-without-a-load

"Most switched mode power supplies are regulated. So as the load is reduced the controller will reduce the pulse width and hence the duty cycle in an attempt to maintain the output voltage.

However as the load is further reduced the pulse width reaches the minimum that the controller can achieve. What happens with very small or zero loads depends on the design of the controller.

1. The controller may maintain the minimum pulse width and duty cycle and allow the output voltage to increase until something goes up in smoke.
2. The controller may maintain the minimum pulse width and duty cycleallow the output voltage to increase until an overvoltage protection circuit is triggered and shuts down the supply until reset.
3. The controller may maintain the minimum pulse width and duty cycle until a self-resetting overvoltage protection is triggered causing wild swings in output voltage as the supply repeatedly shuts down and starts back up.
4. The controller may increase the time between pulses. This allows overall voltage regulation to be maintained down to zero load but it means that the frequency of the output ripple depends on load. This can lead to noise problems both electrical and audible.

My experience is that most modern power supplies fall into category 4 but older designs (which are sometimes still sold) often fell into categories 2 or 3.!"

If your PSU is a $20 pile of junk, I can understand your reticence, but if you've paid at least $100 for an A-tier PSU with a 10-year warranty, you can probably risk connecting it without any "testing".

Remember a "paper clip" test isn't a proper test. You need to put a PSU through its paces with programmable electronic loads, as performed by hardware reviewers on Tom's, if you want to check a PSU's maximum output power, ripple voltages and protection features,