Does this work?

[rambow]

I heard if you put a 100watt light bulb to the top of a capacitor, if the cap is charged it will light up the light bulb and keep it lit until it is no longer charged.

Either way, I have my heart set on opening up my psu and changing the fans. One of them literally sounds like a vacuum and the psu is ~8 months old, im just looking for ways to make it harder to hurt myself. Help greatly appreciated.

 

[MarcVenice]

Hmz, get yourself a big lifeinsurance and try. Make sure you videotape it ?

As to replacing the fan, erm, well I did it too, having 2 left hands didn't make it any easier. But it was basicaly screw open PSU, screw out fan, screw in replacement fan, make sure it's pulling air INTO the PSU, expelling it out of the back of the PC, and screw the PSU back together. Enjoy ?

 

[rambow]

bah. ok, what inside the psu is dangerous to touch, just the caps? the heatsink too?

 

[LOUISSSSS]

heatsink is groudned i believe?

 

[MarcVenice]

Thing is, you shouldn't really be touching any of the inside of the PSU. Perhaps unhook it first, and leave it unhooked for an hour or so before fiddling with it. I never touched anything inside of the PSU though. Just make sure you don't drop any screws in there ?

 

[Jhhnn]

Unplug the computer from the power source, push and hold the power button. This will generally discharge the caps, if they don't have a bleed-off circuit, anyway. Once you get the cover off, handle the unit by what's left of the case, don't go poking around between the case and circuit board, and don't work barefoot on a concrete floor. Changing the fan is really pretty easy, and much safer than handling venomous snakes or some members of the opposite sex...

 

[Rubycon]

Originally posted by: Jhhnn
Unplug the computer from the power source, push and hold the power button. ...

By far the safest way.

A lightbulb is essentially the same as a dead short on a capacitor. Its filament when cold has an extremely low resistance.

 

[Christobevii3]

Never use both hands either when working on this stuff. With only one hand you won't cross a circuit through your body which is where people die from (heart?).

 

[jonnyGURU]

Originally posted by: Jhhnn
Unplug the computer from the power source, push and hold the power button.

Assuming the motherboard will even try to turn on the power supply without the +5VSB being live (won't be if it's unplugged.)

But the general idea here is a good one. If you discontinue AC power to the power supply while there's some sort of DC load, you'll drain the caps. One good method is plugging in a handheld PSU tester and then unplugging the PSU from the wall while the tester is still plugged in.

 

[Jhhnn]

Given that the 5vsb is live all the time, even with the psu shut off or unplugged, the system will try to start, discharging any capacitive charge thru the various loads- the fans will twitch, led's light up, etc. Even the psu fan itself (if capable of operation) will usually serve the purpose if the unit is out of the computer- just jumper the only green wire in the atx connector to any black to achieve the same effect. Some psu's need a load on the 5v and 12v rails for this latter trick to work, so the psu tester would serve the purpose... If the green to black trick will start the psu, set its fan running, then it'll also discharge it, as well, if the input power has been removed.

http://pinouts.ru/Power/atxpower_pinout.shtml

All of this, of course, is strictly at your own risk...

If any of the capacitors look like these, then you're really better off just buying a new unit-

http://pc-medic.blogspot.com/2006/10/leaking-capacitors.html

 

[rambow]

Originally posted by: jonnyGURU

Originally posted by: Jhhnn
Unplug the computer from the power source, push and hold the power button.

Assuming the motherboard will even try to turn on the power supply without the +5VSB being live (won't be if it's unplugged.)

But the general idea here is a good one. If you discontinue AC power to the power supply while there's some sort of DC load, you'll drain the caps. One good method is plugging in a handheld PSU tester and then unplugging the PSU from the wall while the tester is still plugged in.

if what you say is true then couldnt i just unplug my power supply from the wall while my computer is still on? (maybe make sure my hdd is outta there first)

should I buy a power supply tester just to make sure my caps are drained? also, wouldn't i be safe if i wore rubber gloves?

 

[rambow]

Originally posted by: Jhhnn
Given that the 5vsb is live all the time, even with the psu shut off or unplugged, the system will try to start, discharging any capacitive charge thru the various loads- the fans will twitch, led's light up, etc. Even the psu fan itself (if capable of operation) will usually serve the purpose if the unit is out of the computer- just jumper the only green wire in the atx connector to any black to achieve the same effect. Some psu's need a load on the 5v and 12v rails for this latter trick to work, so the psu tester would serve the purpose... If the green to black trick will start the psu, set its fan running, then it'll also discharge it, as well, if the input power has been removed.

http://pinouts.ru/Power/atxpower_pinout.shtml

All of this, of course, is strictly at your own risk...

If any of the capacitors look like these, then you're really better off just buying a new unit-

http://pc-medic.blogspot.com/2006/10/leaking-capacitors.html

given that I have a motherboard to try to turn the computer on, i've wouldn't to jumper the psu, right?

Why do you mention leaking capacitors? the only thing wrong with my psu is the fan (bearing, i can't take the noise anymore)

 

[Jhhnn]

I mention leaking capacitors because they've been a serious problem over the last few years, and because it's hard to tell if that potential problem exists in a psu when the cover is on. While symptoms seem to appear suddenly, they've really been developing over a period of time. It's just smart, and good practice, to clean/ inspect anything like a psu rather closely if you have the cover off for any reason.

The green/black jumper trick also lets you test your work, turn on the psu before putting it back in the case.

 

[jonnyGURU]

Originally posted by: Jhhnn
Given that the 5vsb is live all the time, even with the psu shut off or unplugged....

The +5VSB isn't live if the PSU is unplugged OR shut off. The +5VSB is only live if the PSU is plugged in and turned on and the PC is off (soft off) or on.

 

[Jhhnn]

Uhh, no, jonnyGURU.

Take an atx psu, plug it into the wall, make sure the switch on the back is "on". Put a digital VOM across the purple and any black at the 20 pin connector.

5V, right?

Now turn off the switch, or unplug it- notice how the voltage stays up at the meter for awhile... it's actually dissipating the stored charge thru the meter... and the 5vsb circuitry.

Depending on whether or not the given unit has a bleeder circuit across the caps, their size, and the quality of electrical isolation, that residual charge can remain for some time... so long as there's sufficient stored potential available from the upstream storage devices, the caps, to operate the 5vsb circuitry, it'll be live...

I hope that makes sense...

 

[jonnyGURU]

Right... for a while. Exactly what we're talking about here. So are you just stating the obvious? (that sounds harsher than what I mean, but....)

Until the primary caps and/or the secondary caps for +5VSB filtering drains, yes... it's live. It doesn't hold a voltage by design and when the +5VSB is drained doesn't mean that all of the caps are drained.

That was my point.

It sounds to me that you're stating that once the +5VSB is drained, all the caps are drained. And I'm just saying that if that's what you're saying, that's wrong.

 

[SparkyJJO]

I've poked around inside many a PSU and never gotten hit yet...

 

[Rubycon]

Originally posted by: SparkyJJO
I've poked around inside many a PSU and never gotten hit yet...

Looking at your nick, there is some irony there.

Oh heck just fill it with steel wool.

Electrolytic capacitors discharge fairly rapidly on their own in the open. When connected to a circuit they will discharge much faster. If you're worried about it, pull the power supply out of service and unplug it. Take a lunch break and by the time you come back it will have pissed most of the electrons out of storage.