Question PSU clicks about 2 seconds into boot cycle. PC boots normally as always. Only happens once at this point in the boot cycle, never when in use.

[Fastfishy2]

Not much else to say. Brand new RM750x 2021. I assumed it's just the power transient relay or something activating in the boot stage. Basically I can turn my PC on, it's on for a few seconds before the click happens, and really it just boots as normal as it did with my previous PSU (also an RM750x). Only difference here is the click 2-3 seconds after the PC has already powered on.

Yes, all mobo standoffs are in, and in the correct place.

 

[Lafong]

Sounds exactly like relay behavior.

Some PSUs do it; some don't.

I wouldn't worry unless problems develop.

 

[Fastfishy2]

Sounds exactly like relay behavior.

Some PSUs do it; some don't.

I wouldn't worry unless problems develop.

Righto. And is it normal for it to happen a couple seconds after the PC has lit up and fans are running? I'd have thought it'd be immediate.

 

[Lafong]

Been a long time since I had a PSU that had that click, but as I remember it was NOT immediately after I hit the power button....but probably within 2 or 3 seconds.....going purely from memory. Just a simple one time click.

 

[Fastfishy2]

Been a long time since I had a PSU that had that click, but as I remember it was NOT immediately after I hit the power button....but probably within 2 or 3 seconds.....going purely from memory. Just a simple one time click.

yeah that sounds about right.

 

[Misgar]

The click you're hearing is probably coming from the bypass relay and is perfectly normal. i've never heard an ATX relay click, but most of my PCs have numerous fans, drowning out quiet noises.

Higher quality ATX PSUs incorporate a relay to bypass (short out) the NTC thermistor after it has done its job of limiting the large switch on surge current. In the photo below, the relay is the blue box and the green disc behind is the thermistor.

https://www.tomshardware.com/reviews/power-supplies-101,4193-9.html

 

[The Guy From The Thing]

The click you're hearing is probably coming from the bypass relay and is perfectly normal. i've never heard an ATX relay click, but most of my PCs have numerous fans, drowning out quiet noises.

Higher quality ATX PSUs incorporate a relay to bypass (short out) the NTC thermistor after it has done its job of limiting the large switch on surge current. In the photo below, the relay is the blue box and the green disc behind is the thermistor.

https://www.tomshardware.com/reviews/power-supplies-101,4193-9.html

I have a Phanteks Revolt Pro 1000w and yep, it makes a pretty noticeable click when turning on and turning off, although you can hear it a lot more when shutting down the PC, since you don't have all the fans going on at once


worried me at first but I saw that it was normal for the bypass relay to make a click especially on higher quality PSUs; I've had this power supply for about 6 months now, doesn't seem to any issues so yeah, not a problem

 

[Misgar]

I remember the contactors (relays) in a three-phase 25kW DC power supply at work kicking in with an audible thump you could hear across the other side of the room.

 

[Teknoman2]

I have a question regarding that clicking. My Seasonic focus PX-650 was not making that click while i was using the AM4 Asus Prime board. After a switched to the AM5 MSI B-650 tomahawk it started doing it both at start up and shut down. The only time i didn't hear it do the click on shut down, i came back from work to a dead PSU and mobo. Now i'm always on the lookout for the click and i even pull the plug when i shut down the pc just in case.
EDIT i completely forgot the question. is the clicking related to the motherboard? like the board sends a signal to operate the relay or something?

 

[Misgar]

Most good quality ATX PSUs have a relay to bypass the MOV after its done its job of limiting the the switch on current surge (typically 40A to 100A on the AC line input).

It's perfectly normal and nothing to get excited about. Read a few reviews of PSUs on Tom's and you'll soon get the picture.