Is it dangerous to change the fan on a PSU?

[Nick644622]

It is when a SMPSU is on that it is dangerous. It ups the voltage into the thousands at high frequencies & is prone to explode, hence the metal box. If it is powered up it should be encased in it's box or full protection worn including a full face mask.

 

[ElectroBlaster]

Well afaik the caps are there to store electricity, the transformer just takes the input and converts it?

Also I never work on anything thats plugged in, always remove power leads.

 

[Energize]

Capacitors charge up by moving tons of electrons from one plate (making it positivley charged) to another plate (making it negativley charged), this can create a very high potential difference (230v in this case) causing electrons to move through your body to the positivley charged plate when you close the circuit.

A pc psu uses a step down transformer which is simply two coils of wire wrapped around an iron core, the coil of wire on one side has a current passing through it from the mains, which causes an electomagnetic field to be induced in the iron, which then generates a much lower voltage in the other coil of wire and a much higher current, which is supplied to the output terminals. Hence why a pc can output 50A through the 12v rails despite the mains being only 13A and the output being such a low voltage. It does not store charge.

 

[thegoonden]

A length of wire storing charge?
That's a new one on me I must say.

Any shock you get from a transformer will be a kick-back from a smoothing capacitor.

 

[thegoonden]

I am puzzled as to why that should be ?

If you mean the bit about the caps doing no harm, it's because the caps on the LV side of the transformer probably do not have enough kick to breach (DRY) human skin's natural insulation.
High Voltage ones (not that you see them much in PC PSU's there's usually almost nothing on the HV side of the coil), WILL shock you and you WILL be sorry....they can spasm your muscles hard enough to throw you rather further than the world long jump record.



If you mean the bit about the transformer storing power....I dunno, he must have got that from a Godzilla movie or something.

 

[Servo]

If in doubt about changing the fan in a psu, do what I do, let the wife change it!

 

[PCZ]

It's quite safe IF you follow the precautions

Do the work while someone else is about, so they can call an ambulance if required.

If you need to ask how don't do it.

 

[Munky1080]

VOLTAGE WONT KILL YOU

Didn't Tesla prove it by putting very low amperage through his own body at something silly like 20,000 volts?

 

[pingwing]

Shall we all go back to GCSE physics to learn how electricity works, especially i as all of this sounds sort of right but i was more interested in half the girls in my science class. Probably the best idea is just to leave the psu in a corner for a week and then do it, i dissmantled a really old, cheap and non branded 300w psu just to see what was inside and curiosity didnt kill the cat (and tie lead weights to its feet and throw it in the river), aka i was fine. My mate was terrified that i didnt know i could have killed my self but meh just wait for it to discharge and dont poke anything with something metal and it will be fine....

 

["andy"]

Also, PSU's are controlled electronically by the motherboard. turning it off at the mains/unplugging it and then pressing the power button will do NOTHING. it WILL NOT discharge the caps inside.

since you like capitals... WRONG. well on my old cheapo (competitor PSU) it did

you cold unplug the psu and ten mins later press the power button. the charge in the caps would spin up the fans for a few seconds. i could then prod around inside with a scredriver for as much as i wanted. well i never got shocked

anyway you dont even need a motherboard to power up a PSU so i cant see how what your saying could ever be right ???

maybe it doesnt do that on new PSUs though.

 

[mdjmcnally]

as long as you know what you are doing then its fine, I have changed the fan in my PSU many times before

Emphasis here is if you know what you are doing. If asking then probably don't know what doing.

 

[ElectroBlaster]

If in doubt about changing the fan in a psu, do what I do, let the wife change it!

lmao

 

[FatRakoon]

No, the bit about the xformer I didnt say that it stored power.. Did I?

Anyway, no, I meant that if its on, you can get a kick from it... At least I seem to!?

 

[Edinho]

I wouldnt have though an unplugged PSU capacitor would have the potential to kill. It might hurt a bit but kill? I'd doubt it. If you do it plugged into the mains then you deserve to die for being so stupid.

 

[thegoonden]

No, the bit about the xformer I didnt say that it stored power.. Did I?

Anyway, no, I meant that if its on, you can get a kick from it... At least I seem to!?

Someone did


But yeah, if it's on, the LV side of the transformer itself can give you a sting, and a bloody nasty one as you'll get everything it has to offer, the HV side will of course have a damned good go at killing you.

That chap above with the machine that ran the fans for SECONDS on the capacitors, WTF manner of PSU was that. Normally, they kinda "kick over" and not much else.

There's a thing.........
When the power goes off, the residual momentum in the fans turns them into generators until they spin down. Maybe those pretty blue LED's serve a practical purpose?