[SOLVED] Loud bang from PC

[marwinewert]

My PC just made a loud bang (can't tell for sure, but it did sound like a capacitor exploding) and turned off immediately after, but it managed to boot itself back up right away without me pressing the power button. I only used the pin to log in and check if all the hardware showed up normally and if it had anything in the events , the only one that was showing was the kernel 41 I think. Turned it all off as quick as possible and unplugged it from the wall. It's late and I can't check the mobo because I can't use lights right now, but will check first thing in the morning. My question is... Does the PSU have anything that would make that pop sound? It's a Corsair CX750, there was no smoke or smell. And it did boot itself back without any problems... If the mobo doesn't have any burnt marks or blown capacitors I'll probably try and see what I can do to replace the PSU. The whole system is brand new, a month since I've build the PC.

 

[Darkbreeze]

Yes, the PSU has capacitors just like the motherboard has capacitors. If something made a loud "bang" and it shut down, then there ought to be something visible somewhere. Don't open the PSU and go poking around in there though. It could be dangerous for you, seriously.

I'd visually inspect the motherboard and then using a flashlight see if you can see anything inside the PSU. Does your CX750 have green lettering on the side or is it black lettering on a gray banner?

 

[marwinewert]

Yes, the PSU has capacitors just like the motherboard has capacitors. If something made a loud "bang" and it shut down, then there ought to be something visible somewhere. Don't open the PSU and go poking around in there though. It could be dangerous for you, seriously.

I'd visually inspect the motherboard and then using a flashlight see if you can see anything inside the PSU. Does your CX750 have green lettering on the side or is it black lettering on a gray banner?

My PSU is the gray version, the motherboard is a ASUS X570 TUF Gaming

 

[Darkbreeze]

There are other things that can pop. Do a complete visual inspection and check ALL cables and devices including drives, fans, etc. for any signs of black marks or heat damage.

 

[AllAboutComputerRepair]

Maybe just an extra filter cap in the PSU... your voltage has a little more ripple than normal? I wouldn't power it back on without a complete test of the PSU. You can test the ripple on the +5V and +12V and whatever else with the AC rms setting of a voltmeter.

From https://blog.nzxt.com/the-secret-to-buying-a-good-power-supply-2/

"The output capacitor is charging and discharging continuously to create an AC based on nominal output voltage. Ripple noise is measured in mV (milli-volts). Ripple noise is variable and changes according to load. In Switching Mode Power Supplies, ripple noise is impossible to completely remove, so 1% of nominal output voltage has been set as the standard for ripple noise. Computer PSUs use +3.3V, +5V, +12V, -12V, and +5Vsb outputs, with Intel defining the standard of ripple amount"

50mV to 120 mV is the max it should be (depending on the voltage). But this is Vpp (peak to peak). So rms of a square wave is Vpp / 2, rms of sine wave is 0.707 x ( Vpp / 2)

On your meter you shouldn't see much more than 20 mV rms or 0.020 V rms. Anything more should suspect a PSU failing. But to be sure check against a duplicate PSU.

A blown cap would show way more ripple like 1 Volt, if it was bad enough

 

[marwinewert]

So, I checked everything and couldn't find anything on the motherboard, what a relief. But the PSU itself didn't seem to have anything wrong either, the only thing I noticed was that the capacitor below the area where the cables leave the PSU was bent sideways (almost 45°), but wasn't bulging or anything. There was no burnt smell and no visible damage.
I changed the PSU just to be safe and will probably ask for a replacement.
Thanks for the answers

 

[Darkbreeze]

Well, that's crazy man. I think this is the first time, ever, I've heard of a system making a loud bang but there was no visual or physical evidence of it afterwards. LOL.

You SURE it was the PC, and not something else? If it was, then that's crazy for sure.

 

[marwinewert]

Well, that's crazy man. I think this is the first time, ever, I've heard of a system making a loud bang but there was no visual or physical evidence of it afterwards. LOL.

You SURE it was the PC, and not something else? If it was, then that's crazy for sure.

I'm sure it was the PC because it did shut down right after the sound. I even checked every LED on my components to see if it wasn't one of them, but found nothing. This is my first build btw, really awesome to have something like this happening right away

 

[Darkbreeze]

Yeah, no doubt. I'm sure it probably put your heart in your throat as well and tightened up your nether regions as well. LOL.

I guess the good news is that if everything seems ok, then at least it wasn't something catastrophic and I suspect that it must have been something in the power supply because if it was bad enough to cause a bang, it would surely be visible on the motherboard.