# Discharge PSU capacitor by holding the power button?



## NoviceTechie

I forgot where I read this from, but while I was reading up on how to assemble/upgrade a computer, I was told that when I was changing any components, I should power the unit down, flip the power supply switch to "off," then hold the computer power button for 30 seconds or so. The logic behind it was that it would discharge the capacitor or get rid of any trace amounts of electricity on the motherboard - is that true or a waste of 30 seconds??


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## gcavan

I don't know if that procedure makes a difference or not, but I use it myself, though I don't wait 30 seconds. It is actually draining residual charge from the power supply which will be instantaneous. Ask yourself this: Could you replace your computer with the money you could make if you spent that 30 seconds in other ways?


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## Tyree

I hear of people doing it but I never have. If it makes you feel better, do it.:grin:


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## LMiller7

I cannot be certain but I very much doubt holding the power button will do anything. But it is a good idea to wait 30 seconds as large capacitors can take time to discharge. 30 seconds is probably longer than necessary but it is better to be safe than sorry.


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## Tumbleweed36

This issue is up to debate. Personally, I have never done that and it has not caused any issues for the positive or negative. Personal preference should be your guide.


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## NoviceTechie

I don't know if it makes a difference, but last night when I was installing a new fan - I shut the entire computer down, when the fans stopped spinning I turned the PSU switch to "off," then immediately while the motherboard electricity indicator light was still "on" (indicating trace amounts of electricity still on the mobo) I held the power button for at least 15 seconds. In the first second the computer actually turned on for half a second, so there really was some trace amounts of electricity in the system.

Maybe the motherboard would have dissipated that excess electricity if I had not pressed the computer power button immediately after I turned off the power supply, I assume that LED mobo electricity light indicator does drain the mobo of trace electricity if left alone, but holding the power button does seem to help if ur in a rush to install a new component q;

(One quick question, if a computer powers on for half a second like that - would it cause any damage? I assumed no since it hasn't even completed its POST test and any memory on the motherboard's side (aside from cmos) is volatile and just reset when the electricity's gone, but thats just a text book guess >.<)


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## 1 g0t 0wn3d

I believe the only issue of a computer turning off at any point in time comes when modifying system files, or flashing the bios. Other than that i haven't seen any problems since nfts came about.


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## sleets

I have a related problem which proves that draining the capacitors matters at least at certain situations. 

My problem is the computer does not POST if I do not drain the capacitors. My computer works great without any issue if it boots up. The problem is if I shutdown my computer from 'Start' menu and leave it for some time, say overnight, the next morning I cannot boot it, no POST screen. The method to fix it is exactly the draining of the capacitor: remove the power cord, pressing the power button for 30 seconds, plug the power cord back in, and press the power button, it will boot up and everything works from there.

Any though? I really don't want to do this draining everyday. Thanks.


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## Tyree

Sounds more like a failing PSU.

PC Specs?
Pre-Built Brand & Model Number
Custom Built-Brand & Model of Mobo-CPU-RAM-Graphics-PSU.


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## sleets

It is a self-assembled system:

Case: Antec Fusion v2
Motherboard: Asus P5K-VM
CPU: core-2-duo 6550
Memory: 2GB DDR 2 800Mhz Crucial Ballistix (Heard bad review of it recently)
Hard Disk: Western Digital 250GB Green Cavalier
DVD Drive: Asus something

It must be one of PSU, memory or motherboard. I also noticed I cannot standby or hibernate.

Thanks,


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## GZ

Can you list the Brand/Model/wattage of your PSU.


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## sleets

It came with the Antec Fusion v2 Media Center case so I think its brand is Antec. I did not find its model but here is its description: Quiet high-efficiency 430 Watt ATX12V v2.0 power supply with universal input, active PFC

It is this case: http://pcpowerzone.com/fusion.html

From BIOS Power section, I saw:

VCORE Voltage: 1.312v
3.3V Voltage: 3.2v
5V Voltage: 5.04v
12V Voltage: 12.04v (I saw 11.98v also, it changes between these two numbers)


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## GZ

Antec PSU's used to be high quality. They have had issues in the recent past. Also, the PSU's shipped with cases are usually worse.

Your voltages look okay and are all within spec, but you had to 'discharge' residual energy to get the computer to start, so those readings may be false.

I suggest you replace the PSU with a high quality Corsair or Seasonic unit with a bare minimum of 550w.

I suspect your issue lies within your PSU as Tyree suggested earlier.


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## sleets

One more thing, right after shutdown, it can boot up again. It is only after certain hours, it will have the problem.


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## sleets

Another thing, reset button (sometimes maybe) works when power button does not. I read some where that reset button is similar to the switch on the power supply that it disconnects the power from the motherboard momentarily.


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## Tyree

sleets said:


> One more thing, right after shutdown, it can boot up again. It is only after certain hours, it will have the problem.


That also sounds like a failing PSU.


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## LMiller7

The reset switch doesn't have anything to do with power. It momentarily activates the reset line to the CPU and other devices.

As others have said, the problem appears to be a failing PSU.


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## sleets

Thanks for all the replies. I will live with the POWER + RESET start for now and look for a PSU in the meantime.


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## originalquene

Hi, I just had an experience that can tell you the capacitors do have residual energy that can affect the computers performance, I have a laptop which during a system recovery it just turned off, and then wouldn't turn back on, it just would stayed on for at much 2 secs, then someone at the support chat of Acer told me to remove the battery and hold the power button to eliminate the residual charge of the motherboard, he told me that a computer is supposed to eliminate the residual static charge but sometimes it doesn't happen and due to this the motherboard protects itself by turning off

hope my experience works for somebody


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