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Relation between PSU failure and UPS?

RealPerson15

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Oct 12, 2020
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My PC has been turning itself off at random lately (it happened twice just today) so I figured my ancient PSU is about to kick the bucket. But my brother is telling me it can't be the PSU, because if that were the case the UPS it's connected to would "activate" or give some sort of signal when the PC crashes. It this true?
By the way, the crashes are instant, the PC turns itself off while not under any significant stress. Once it also immediately turned itself back on after crashing.
 
I don't know much about a UPS, but if the power supply is bad the UPS won't stop you from crashing (which, by the way, the system instantly powering itself off is characteristic of PSU failure). I'm not sure if it would throw any errors or anything for that, either.
 
The UPS can be bad as well.
 
But my brother is telling me it can't be the PSU, because if that were the case the UPS it's connected to would "activate" or give some sort of signal when the PC crashes. It this true?
No.

The only time the UPS would give some sort of signal would be if a connected device (like the computer's power supply) developed a serious fault that resulted in an unsafe condition - like trying to pull too much power from the UPS. Then the UPS would (or should, anyway) immediately shutdown to protect itself and the other connected devices.

so I figured my ancient PSU is about to kick the bucket.
Even brand new PSUs from the best makers can fail. So regardless the age, you need to swap in a known good PSU and see what happens.
The UPS can be bad as well.
This is true, but normally, if the UPS is faulty, it either will not power on, or it will fail to kick over to batteries during a power outage.

UPS are simple to test. Some connect to the computer through a USB data cable and come with monitoring software. Typically, this software lets you run a self test. If this applies to you, run the test.

If your UPS is not connected to your computer via a USB data cable, connect a couple table lamps to the UPS - preferably with standard incandescent 60 W light bulbs. LED lightbulbs don't consume enough wattage for an effective test. Turn on the lamps then unplug the UPS from the wall. Does the UPS kick over to battery and keep the lamps lit for more than a few seconds? If not, the UPS is bad or more likely the UPS batteries need replacing. Note UPS batteries normally need to be replaced every 3 - 5 years as part of normal maintenance.
 
Actually my brother's pc is also connected to the ups (it's not overloaded) and his PC doesn't crash.
 
UPS job is to protect from sudden power surge and depending on the model also to smooth out the current. You have bad power supply.
 
Actually my brother's pc is also connected to the ups (it's not overloaded) and his PC doesn't crash.
This further suggests the UPS is fine. And while your PSU is the primary suspect at this point, you cannot - yet - conclude your PSU is bad. Sudden shutdowns can be caused by bad RAM, faulty motherboard, bad CPU or other failing components. But since EVERYTHING inside the computer depends on good, clean, stable power, you need to swap out the PSU to make sure you are supplying that good, clean, stable power. If your computer shuts down with the 2nd PSU, your current PSU is not the problem.
 
Faulty cooling can also cause this behavior.
 
Is there any way of seeing which component is causing this without buying a bunch of new ones? (warranty is out on all of them and I don't have much cash at hand)
Also, thanks for the help so far.
 
I already noted that you need to start by swapping in a known good PSU. Perhaps swap out the PSU with your brother's computer. You cannot assume any other component is bad (or good) until you verify you are giving it good power.
 
Keep us posted!
 
But my brother is telling me it can't be the PSU, because if that were the case the UPS it's connected to would "activate" or give some sort of signal when the PC crashes. It this true?

He's ignoring the fact that either can fail. And that the UPS protects the pc from the power issues resulting from the wall, ie. the grid. However the PSU could still fail from degradation so his comment is very misinformed.
 
My PC has been turning itself off at random lately (it happened twice just today) so I figured my ancient PSU is about to kick the bucket.
Looking at the event viewer can help pinpoint the problem.
 
Start with the "stupid" simple things.
Is the power cord properly plugged in on both ends? Does it get hot when in use?
Has the system been cleaned?
Are there any fans that aren't running?
Does the 24 pin connector look okay and is it seated properly? (check with power plug disconnected)
Does the EPS (CPU) power connector look okay and is it properly seated? (check with power plug disconnected)

BTW, what PSU do you have?
 
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