Hi i've been told that there are electric charges in the psu even after you plug it out of the wall and ground the mobo, so i was wondering if there's any way to "make it go away" so that i don't get a case of the death? The reason is that i want to change the outer measurments so that it fits in my "to be mod"
All of the newer power supplies will drain the capacitors on the high voltage side of the power supply within a few seconds. You can discharge them yourself to make sure using an insulated resistor and checking with a multimeter afterwards. While no more lethal charges are present, some of the capacitors smoothing the 3.3V, 5V and 12V lines will still be charged and may make you jump if you accidently discharge them with a piece of metal - so same goes for those - discharge them with a resistor. DON'T discharge any of the capacitors with a screwdriver - it can easily damage the capacitors as they are not intended for such high peak currents.
when you say that it will drain in a few seconds, do you mean like after i ground the mobo or a few seconds after i simply turn the computer off? well i can get a hold of the multimeter and the resistor, but just to be clear the capacitors are thos fatassed cylinders right? the PSU is 3 years old but im guessing thats new enough?
They have a highish resistance resistor across the terminals, so once the mains is removed they'll discharge. Grounding will probably do nothing, you have to put the resistor across both of the capacitor leads, not between them and ground.
You could also just wear rubber gloves. I use nitrile gloves when messing with car batteries or main lines. Mainly because they are so puncture resistant, small chance of tearing and allowing my skin to touch anything. It's not really necessary if you take the proper precautions...I mean, I know what I'm doing, I'm just worried that someday I'll slip.
well that kind of goes without saying even though i usually just jump right in when it comes to new projects
when im working with car batteries getting **** on my skin is my least problem, im just worried about getting acid in my eyes
mental note too self, don't touch the psu heatsink while the computer is running, and if you'll exscuse me i gonna hit the shower since it started a major sweatwave
correct, they arent grounded, and between some points in a power supply you can get 300+V Easist way to discharge the caps is to either kill the power while the computer is on, or to press the power button, after you pull the power (it should start to power up for a split second), that makes it try to use what little power is stored in the main caps. Though testing and discharging once you have it open is definiely a good idea.
well thats what ive been doing every time im adding/removing parts in the computer, and thats what i meant with grounding the mobo so does that actually discharge it totally?
On this topic. Yesterday I accidentally discharged a fully charged (disposable) camera flash into my finger. It hurt. A lot. My muscles were still twitching (a lot) for about 5-10 seconds after I managed to drop it. ...And I have the burn marks on my finger to prove it. lol So yeah, be really careful.
I wouldnt short out anything on the mobo... but it should dischage it. If there arent bleeder resistors, the caps can build a charge back up, and zap you if that isnt bled off again... but if there is a bleeder it should keep that down.
so what youre saying is that the caps will fill even with the powercord out and the powerbutton pressed a couple of times?
They can recharge due to charge redistribution, but this usually happens within a few seconds, so by the time you're testing with the multimeter you'll be able to see if the voltage isn't 0V.
On the topic of discharging using the power button method, would that not nessecarily drain the power because it only takes a few volts fomr the PSU to boot the Mobo. Say if it needed 3 volts to jump the mobo and the PSU's capacitors could store 300v, you'd have to press the power button a hundred times? i klnwo thats kinda simplistic, but does that make sense? By the way, i recently replaced a fan in my PSU using this method, and i'm living to tell the tale.
