Do you need to short and how if, PSU capacitors?

Apr 22, 2018
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Hi. My question is do you need to short the power supply capacitors to be safe working or cleaning inside. If so what's the right way to do it.
 
Solution
If you knew what you were doing, you would have either:
1. Just done it, or 2. Known it was a bad idea.
This is not something we can talk you through from out here.

And remember, you're not the only one reading this. Hundreds, possibly thousands, of others will read this in the future. Many with far less skills than you.
Someone would take a basic set of steps (Oh look...Nikola did it!), and try this with a whole different unit, thinking it was a good idea. Fried fingers or worse.
Not recomended. The capacitors may be charged by a voltage that is above the voltage of your main socket.
That may both cause damage to other components because of current spikes and it may even go through your hand. Happens to me some twenty years ago, and my hand never recovered completely from that.
 
Apr 22, 2018
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I'm talking about working inside, so i know they can hold a charge, i heard some are insulated on the cathodes. Anyways yeah, unplugging it and turning it on couple of times probably drains them but my question is do i need to flip the board and short them with an insulated screwdriver to be safe working/cleaning inside. I'm asking also if i ever need to replace a capacitor to be safe and sure how to do it.
 
Apr 22, 2018
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I'm talking about pulling it out completely and for example cleaning. I know capacitors are dangerous so i'm asking how to drain them properly. Can you just short the cathodes with an insulated screwdriver?
 

USAFRet

Titan
Moderator
"Cleaning inside"
Just blow air through the fan vent and the outlet holes. Blowing the dust out.

If it is dirty enough inside where that does not work, you need a newer PSU. And a better airspace that it lives in.
Don't take it apart.

And if you're asking the question of what to short to make it safe to poke around inside...you personally really don't need to be doing this.
 
Apr 22, 2018
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So how do i remove the danger, example i need to replace and re-solder something. I am planning to buy i new psu anyway but i want to clean this one before i sell it. But i'm asking purely to improve my knowledge because i studied electronics short time ago.
 

USAFRet

Titan
Moderator


PSU's are not consumer fixable, without a LOT of experience and training.
And this is not something that can be talked through in a forum like this.

If you do this, go to your local hospital emergency room and do it there. That way, at least you'll have a med team right there to maybe get your heart started again.

Just blow air through it, both directions.
 
Apr 22, 2018
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It's okay man sheesh, i worked in an IT service for high school practices and made pcb's before (IM NOT BRAGGING). I want to get a similar job now too, im not just gonna stick my fingers in 220 volts like in some jello. Is it not allowed to discuss this on this forum, because it's potentially dangerous? Don't get me wrong i'm not trying to be cocky, i just want to study some stuff over again. I'm not just a consumer, i want to be more.
 

DSzymborski

Titan
Moderator


Here's the thing. Someone who is qualified to do what you wish to do would also not need to ask these types of questions. Ethically, most people don't want to be involved in giving advice to could be dangerous to the wrong person. If you had asked a *very* specific question about a *very* specific part, you may have gotten some feedback, but first you say that you want to clean the PSU and then, all of a sudden, now you want to re-solder "something" inside. There's a basic element of trust that's a problem here.
 

USAFRet

Titan
Moderator
If you knew what you were doing, you would have either:
1. Just done it, or 2. Known it was a bad idea.
This is not something we can talk you through from out here.

And remember, you're not the only one reading this. Hundreds, possibly thousands, of others will read this in the future. Many with far less skills than you.
Someone would take a basic set of steps (Oh look...Nikola did it!), and try this with a whole different unit, thinking it was a good idea. Fried fingers or worse.
 
Solution

Karadjgne

Titan
Ambassador
Unplug the pc. Hold the power button down for 15-20 seconds. That'll be enough to drain any caps.

And no, you do not directly short a capacitor with anything like a screwdriver. It's only done with a resistor to take up the load. And the resistor must be rated higher than the capacitors discharge or it'll burn up.
 


Aside from what USAFRet already said, this is exactly right. Although it might ought to read more like "Somebody who can SAFELY do what you wish to do, would also not need to ask these types of questions AND would likely never need to go anywhere looking for answers".

If you don't know how to work in or around electronics that use stored energy, you shouldn't. Period. Unless it's alongside a highly skilled instructor. And contrary to what has been previously expressed, discharging the caps by pressing the power button does not make everything inside the power supply, or other electronics, completely safe. In some cases, it may not do anything at all to certain components.
 
Apr 24, 2018
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Not to jump on the bandwagon too much here, but I'd also reconsider the concept that because you're going to sell it, it's cool to open it up and do a bit of soldering in there.

It is, generally speaking, a non-user serviceable part. As a potential purchaser, I'd have an expectation that buying your PSU would imply that you hadn't self-serviced it.

Dare I say that it's a bit unethical to on-sell a PSU which has been modified or otherwise serviced in a non-quality controlled, professional environment. I mean, the system (or person) you fry may not be your own.

Just a thought.
 
Apr 22, 2018
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Like i said earlier i'm bending my brain with the english because it's not my native, i'm not good at elaborating myself sometimes. The specific question is if i need to clean it inside do i need to drain them, and next question how to do it, i'm pretty sure you just turn the pc on after it's plugged off, short the cathodes and look away. But there's dielectric absorption, so i guess no short answer for this one. Actually no, the first problem was that first time in my life i had coil whine in my life. I'm pretty sure it's the psu and it's a cheap one because you know, pre built system. So i wanna sell it now actually, but for some reason after cleaning it with compressed air (not compressor) it stopped for some time. So it's probably coil whine or a bad amount of dust maybe in the middle of fan who knows, that the can just can't clean. So, that's why i want to open it and clean it out, actually my question would be how to fix my asking skills jesus haha
 
Apr 22, 2018
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I'm trying to reply to everyone sorry if i sound blatant, yeah man i agree but i don't think i'm gonna sell it, not to be rude but it's probably crap. It's some brand called codegen, and sounds like a boeing engine. So, it's probably worth 10 dollars new, eh i don't know. But actually i still want to clean it, so i might have to take it out to a gas station near me because they have a decent compressor, and my compressed air can is not enough to clean it properly. So basically i need to clean it to be more buyable and if i use it more, because i still need it, maybe to sound less like an airplane taking off.
 
Apr 22, 2018
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Good points, and i totally agree. I'm probably gonna tag this answer as the solution in the end, just to not give the wrong people an idea for disaster. If nothing this inspires me to research deeper. For the sake of curiosity though, do you agree with Karadjgne, i'm not gonna do it just asking.
 

DSzymborski

Titan
Moderator


Eww, a Codegen? That's the kind of power supply I'd take a baseball bat to, just to ensure that nobody at the dump tries to use it in their PC. That Powmax/Leadman-based PSU tend to have Chinese capacitors so horrific that it's hard to even find companies that actually exist to connect them to.
 
A cheap psu like that ??

Not worth opening at all , apart from the fact that the main input cap actually holds a charge of 360-380v not 220-240v - which would give you more than a little jump start , I wouldn't trust it to have bleed off resistors meaning it could theoretically hold that charge for a couple of days.

Quite simply not worth messing around with