Question Computer makes a bang when turned on

TheJJBman11

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Jan 6, 2015
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Hiya,

Whenever I turn my PC off at the wall then back on again it makes a loud bang or pop sound, on the most recent time I also saw a little flash of yellow-ish light coming from the PSU.

Furthermore, today I noticed sparky sort of sounds coming from my PC, it's very rare so I can't determine where abouts it's coming from but surely it's not good ahah.

My PSU is the RMx Series™ RM750x — 750 Watt 80 PLUS® Gold Certified Fully Modular PSU (UK).

Thanks :)
 

jonnyguru

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The damage you're creating comes from "in rush". The PSU has a large "bulk" capacitor in it that needs to be fully charged before the PC can operate properly. To charge this capacitor a large "rush" of power goes into the PSU from your mains.

If the PC is shut down properly in Windows AND LEFT ON THE WAY ATX COMPUTERS WERE DESIGNED TO OPERATE this capacitor stays charged indefinitely.

If you're turning the PC off at the wall because you're afraid lightning is going to damage your PC: Buy an adequate power strip.

If you're turning the PC off at the wall to "save energy", you're not saving energy. Modern PSU's with high efficiency use VERY LITTLE power in standby. You're probably wasting just as much power letting that bulk cap discharge and then having it charge back up again then if you just leave the PC on.

If you're turning the PC off at the wall because it has a bunch of LEDs on the motherboard that annoy you (there should only be one LED on the board that remains on and that's the standby LED), then you need to look in the BIOS and figure out how to turn off the lighting in the BIOS.

BUT STOP TURNING YOUR PC OFF AT THE WALL SWITCH!!!!!!
 

TheJJBman11

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Jan 6, 2015
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The damage you're creating comes from "in rush". The PSU has a large "bulk" capacitor in it that needs to be fully charged before the PC can operate properly. To charge this capacitor a large "rush" of power goes into the PSU from your mains.

If the PC is shut down properly in Windows AND LEFT ON THE WAY ATX COMPUTERS WERE DESIGNED TO OPERATE this capacitor stays charged indefinitely.

If you're turning the PC off at the wall because you're afraid lightning is going to damage your PC: Buy an adequate power strip.

If you're turning the PC off at the wall to "save energy", you're not saving energy. Modern PSU's with high efficiency use VERY LITTLE power in standby. You're probably wasting just as much power letting that bulk cap discharge and then having it charge back up again then if you just leave the PC on.

If you're turning the PC off at the wall because it has a bunch of LEDs on the motherboard that annoy you (there should only be one LED on the board that remains on and that's the standby LED), then you need to look in the BIOS and figure out how to turn off the lighting in the BIOS.

BUT STOP TURNING YOUR PC OFF AT THE WALL SWITCH!!!!!!
I go to uni and take my PC there and back.
 

jonnyguru

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I go to uni and take my PC there and back.
You lug a desktop PC to university and back every day??????

I think you're right. Just took the back of the case off, turned it on and saw a spark comes from the PSU, head the bang then the system shut off. Any reliable PSU suggestions? I'm staying away from Corsair.
LOL!

Did you not read a single word I typed?

YES! There is a spark. You're charging the bulk cap every time you flip the switch.

And "stay away from Corsair"??? LOL! They're only like one of the biggest PSU brands out there.

And if you really do think the PSU is defective (which I don't), why wouldn't you just RMA it under warranty for a new one?????
 

TheJJBman11

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You lug a desktop PC to university and back every day??????



LOL!

Did you not read a single word I typed?

YES! There is a spark. You're charging the bulk cap every time you flip the switch.

And "stay away from Corsair"??? LOL! They're only like one of the biggest PSU brands out there.

And if you really do think the PSU is defective (which I don't), why wouldn't you just RMA it under warranty for a new one?????
Nah but I go home every 3 months so it gets moved a fair bit and warranty will take a while and I need it asap. Surely it cant be right for the psu to be sparking and making electrical noises with casual use?
 

Phaaze88

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Nah but I go home every 3 months so it gets moved a fair bit and warranty will take a while and I need it asap. Surely it cant be right for the psu to be sparking and making electrical noises with casual use?
What you've been doing with your psu over and over(turning it off at the wall), isn't considered 'casual use'...
It's like what jonnyguru has been telling you this entire time hasn't clicked.
You've been damaging the psu yourself the entire time - it's got nothing to do with the brand. It's user error.
 

TheJJBman11

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Well what do you want me to do? Not have a PC for the half a year I'm away? All my friends who go to uni take their PCs and dont have * sparks and bangs from turning it off.
 

jonnyguru

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Well what do you want me to do? Not have a PC for the half a year I'm away? All my friends who go to uni take their PCs and dont have * sparks and bangs from turning it off.
Depends on the build. If the PSU is a cheaper PSU with smaller bulk caps, they require less power for the cap to charge.

Also, depends on your +5VSB load. If you have a bunch of USB stuff plugged in, the surge is going to be greater because it not only has to charge the bulk cap, but also energize the +5VSB rail and everything plugged into it.

The PSU should be fine. Even if it does die from constant on/off cycles, which it shouldn't, the PSU has a fuse, MOV, etc. to protect the rest of the PC.

Question: Does it do this spark and pop only at your home, at the university or both?
 

jonnyguru

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That is true, but it should not produce a spark. Hey the thing may boot up and everything runs, but IT JUST ME I don't want no spark. Your tolerance may vary.
That is true, but it should not produce a spark. Hey the thing may boot up and everything runs, but IT JUST ME I don't want no spark. Your tolerance may vary.
As @kerberos_20 pointed out, he may not even be using the switch on the back of the PSU. Then the arc is just an arc across the switch terminals.
 

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