# PSU Fan Pulsing??



## Inked_ (Aug 16, 2017)

Hi guys 

I posted this in another forum but I think it's more suited here.


I have a psu that's fan is pulsing from fast to very fast.

The computer was just doing some document work when it staryed happening so wasn't under any stress. 

I've swapped it out with an old psu and it seems to be running ok.

I stripped down the faulty psu and gave it a good clean but it hasn't made any difference. 

I've not come across this problem before as the problems are usually either fans running at full speed all the time or not coming on at all.

I was thinking it could be a faulty thermal sensor but I don't think that would explain the fan pulsing. 

Has anyone ever seen this before and know what failed in the psu?


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## Masterchiefxx17 (Feb 27, 2010)

Hi and Welcome to TSF!

Please be warned about opening a PSU! It could cause serious harm or even death.

What is the make and model number of the PSU? How old is it?


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## DBCooper (Jun 11, 2010)

Hi there,

Yes, be careful when it comes to opening computer power supplies and their capacitors carry a charge for days or so even though they're unplug. 

Here's one such article where a 16-yr old teenager died from electrocution when he opened up his computer power supply to fix his computer issue.

http://www.dailymail.co.uk/news/art...lahoma-dies-electrocuted-fixing-computer.html


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## Bill_Bright (Dec 17, 2004)

Not to beat a dead horse, but yeah, the PSU is the one component in a computer that can kill (anything that plugs into the wall can kill). And while bleeder resistors/circuits are supposed to degrade the voltages to safe levels quickly, that assumes the PSU is in perfect condition. Degradation can also be hindered if the PSU is quickly unplugged from the wall, thus removing the path to Earth ground. And to that, I am assuming the wall outlet is properly Earthed. 

Note this is why those "Warranty Void if Broken" tags are legal on PSUs (but not legal on computer cases) - there are no "user serviceable parts inside" a PSU. 

As for your pulsing fan, this could be a faulty sensor circuit, or it could be another component that is failing and causing heat to rise and the fan speed to quickly ramp up. This increase in fan speed could then cool down the supply enough to drop the speed, after which the temps rise again and the circle repeats.

The problem, even for qualified technicians, is power supply makers don't publish circuit diagrams or service manuals for their supplies. So unless you can visually see damage, there is little you can do but replace the supply.


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## Corday (Mar 3, 2010)

Must answer question posed in Post #2 for a possible answer.


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## Inked_ (Aug 16, 2017)

Thanks for all the concern and replies.

I know all about the dangers of PSU's and caps and I dabble in electronics.


The power supply in question is a FSP Group Epsilon 80 Plus 1010W.


Although it's getting on a bit now it's actually not been used that long.


It does this "pulsing" from the moment i turn it on and the air thsts blowing out is cold.


Maybe I have a good look at the board.


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## Corday (Mar 3, 2010)

I lean toward a PSU that steps up to the challenge of higher loads. A zillion watts doesn't impress me so anything in the 650-700 range is good enough for a gamer.


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## Inked_ (Aug 16, 2017)

Corday said:


> I lean toward a PSU that steps up to the challenge of higher loads. A zillion watts doesn't impress me so anything in the 650-700 range is good enough for a gamer.



Sorry but am I missing something here or have you posted this in the wrong thread?


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## Corday (Mar 3, 2010)

I'm not always as direct as I might be. Sorry. You already took care of the most common cause of PSU failure, dirt. Although any of the components might have failed, I was really saying it isn't worth saving the unit. You solved the problem and if you want a recommendation for a good permanent replacement, many here can help.


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