PSU buzz/hum even when switched off

[Wim]

I recently replaced some components in my PC and as plugged my PSU back in I noticed it made a noticeable hum/buzzing noise. I would usually assume this was just coil whine, but it makes this noise even when the PSU is switched off at the back where the cable attaches. I thought coil whine usually only happened when that switch was on?

I've disconnected all my other hardware from the PSU and the buzz still continues. 

Could this be a sign of a more serious malfunction or just normal coil whine? I really don't want to risk blowing the PSU given I was one of the lucky few who managed to get a 3080 on launch day...

Model is SilverStone Strider Gold S ST75F-GS V3 750W 80+ Gold Fully Modular

[manikyath]

15 minutes ago, Wim said:

but it makes this noise even when the PSU is switched off at the back

technically.. this can only happen if there's a bee stuck in your PSU.

[Wim]

2 minutes ago, manikyath said:

technically.. this can only happen if there's a bee stuck in your PSU.

Lol, It's still plugged in and switched on at the wall socket. Just the I/O switch on the actual PSU is switched off.

[MadAnt250]

24 minutes ago, Wim said:

but it makes this noise even when the PSU is switched off at the back where the cable attaches

So you get buzzing even when there is no power?

Maybe Bees?

Maybe a bad circuit from the wall?

Maybe Bees?

8 minutes ago, manikyath said:

technically.. this can only happen if there's a bee stuck in your PSU.

Beat me to it.

[manikyath]

1 minute ago, Wim said:

Lol, It's still plugged in and switched on at the wall socket. Just the I/O switch on the actual PSU is switched off.

if the switch on the back of the psu is off, it should be completely without power.. unless there's something seriously wrong in your house wiring...

[Wim]

3 minutes ago, MadAnt250 said:

So you get buzzing even when there is no power?

Maybe a bad circuit from the wall?

 

3 minutes ago, manikyath said:

if the switch on the back of the psu is off, it should be completely without power.. unless there's something seriously wrong in your house wiring...

Yea, just to be clear the buzzing stops if it's switched off at the wall. I've tested it on multiple different outlets/power cables and the buzzing still happens and there is no buzzing from my partners PC so I'm pretty sure the outlet/house wiring isn't the problem 

[MadAnt250]

3 minutes ago, Wim said:

Yea, just to be clear the buzzing stops if it's switched off at the wall. I've tested it on multiple different outlets/power cables and the buzzing still happens and there is no buzzing from my partners PC so I'm pretty sure the outlet/house wiring isn't the problem 

Maybe a bad circuit in the PSU.

[seon123]

I'm guessing that it's just coil whine from 5Vsb. It will still have power for a bit after you cut power to it, until it has drained the main bulk capacitor.

[Wim]

48 minutes ago, seon123 said:

I'm guessing that it's just coil whine from 5Vsb. It will still have power for a bit after you cut power to it, until it has drained the main bulk capacitor.

Yea but then why does it stop as soon as I turn off the PSU at the wall outlet? Shouldn't it just keep going regardless?

[Guest]

17 minutes ago, Wim said:

Yea but then why does it stop as soon as I turn off the PSU at the wall outlet? Shouldn't it just keep going regardless?

Wait a minute......

 

Switched off at the wall and it stops, plugged in and off and it keeps buzzing?

 

So, the switch on that particular PSU is after the X/Y caps.  It also only cuts the hot and not the neutral. So they're still energized and prone to buzz if the mains are noisy.

 

 

[Wim]

18 minutes ago, jonnyGURU said:

Wait a minute......

 

Switched off at the wall and it stops, plugged in and off and it keeps buzzing?

 

So, the switch on that particular PSU is after the X/Y caps.  So they're still energized and prone to buzz.

 

Yea that's correct.

Wall outlet off = no buzz 
Wall outlet on + PSU off = buzz

Thanks, sounds like this is just normal noise and not "I'm about to murder your nice graphics card" noise. Big relief.

Edited February 26, 2021 by Wim