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Power supply popped and smoked, burned out. What should I test or check?

Today when I  got out of bed, my APC Back-UPS XS 900 was beeping a continuous beep, and the "Overload" light was on,  and both pc's were off.  I turned the APC off, and unplugged one pc from the APC.  Then I turned the APC back on and re-plugged in the other pc I had just unplugged, and I heard a loud 'POP' from the pc, and the APC light went to "Overload"  again.  Everything connected to the APC (both pc's & monitors, Comcast Modem, Linksys Router) turned off.  I saw sparks and smoke come out of the power supply of the pc that I first unplugged.  I unplugged that pc from the APC again and turned everything off.  I wasnt sure if smoke also came out of the APC or not since that electrical smoke is really strong and it is hard to tell what piece of equipment is smoking.  So I  took apart the pc that popped and the pwr supply smells like the smoke.  I am pretty sure that pwr supply is shot, so I will buy a replacement, but do I need to test any of the other internal parts of that pc (system board, peripherals, the Router) to see if they got hit with something from the bad pwr supply?
Thank you,
Mark O'Brien
Mark O'Brien
4 Solutions
Check your UPS by connecting only a desk-lamp - the type with a regular bulb, not one of those energy-saving types.. Let it run down on batteries then recharge it.. Don't plug in any PC's, routers etc. until you're sure it's ok..

Sounds like your PC PSU blew.. Don't ever plug the bad PSU in again - take it out and replace it with a new/working one.. Start by connecting only the motherboard - remove any cards such as graphic adapters and all hard-drives, DVD drives etc. Disconnect everything external - monitors, keyboard, mouse, USB devices etc. and try switching on..

I have seen cases where a failed PSU has damaged the motherboard which then in turn blows the new PSU.. If you're lucky, only the power-supply was damaged and you will be greeted with fans turning and motherboard beeps when you push the power button..

Once you have ascertained that the power-supply & mainboard are working, start replacing parts one at a time.. If you've important information on your hard-drive, buy/borrow an IDE/SATA to USB adapter, connect the drive to your laptop and backup the important files first..
Hate to say this, but you'll be in luck if any of your PC components is still alive.
Some people save mony on PSU's, but this can give you even more expenses. I strongly recommend a PSU from Corsair, Thermaltake, Enermax or similar manufacturers.

You can safely use a new PSU with your components to avoid any future damage and thus check which of your components still work.

But, I wouldn't use APC for now. If an UPS has a power overload, it should decrease it to normal levels, so I suspect on APS too.
APC Back-UPS XS 900 is a "Stepped Sine Wave" type UPS vice a True Sine Wave type.
A Stepped Sine Wave is actually a series of DC pulses at stepped voltage values use to simulate AC
PFC [in a power supply] corrects for the fact that volts and amps are out of phase in line voltage.
AC is out of phase 100% of the time. Stepped DC is out of phase about 5-20% of the time depending on the circuit specifics.

PFC is not designed for Stepped DC, only for True Sine Wave inputs.
When Stepped DC is fed to a PFC circuit the PFC tries to adjust amps and volts 100% of the time and that causes the effective AC volts on the input of the PSU to go as much as 20% higher than the line voltage the PSU is designed for.
- The first stage of an SMPS PSU doubles the line voltage making the input to the next stage 40% higher than it should be.
- If you are on 220v line power that exceeds the ratings of the components in -most- PSU's. Probably like 90%.
- If you are on 120v line power that exceeds the ratings of the components in -some- PSU's. Probably like 5%.

A UPS with a Stepped Sine Wave is an old old design that came into being when few PSU's had PFC.
True Sine Wave UPS units cost -significantly- more than Stepped Wave units.

APC denies there is a problem but I've seen measurements taken from PFC type PSUs connected to Stepped Wave UPSs where the voltages on the capacitors in the first stages of the PSU were at 110-120% of their max voltage rating.

I would inspect PSUs for blown capacitors and/or burnt rectifiers and diodes.

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If you want to use a Stepped Wave UPS with a PFC PSU then you need to make sure the input caps in the PSU are rated for at least 440-450v.
400v caps are most common in cheap or older model PSUs.
Just one note to Back-UPS: They simply don't like PCs with Active PFC (many modern power supplies have it). Back UPS is not dimensioned to supply Active PFC and they will burn in months or sooner. The Overload state on UPS switches on even when no device is connected after the malfunction.

If your PC power supply is broken be ready to replace almost any component in your PC. Fortunately, warranty may apply to some of them but data recovery is expensive action with no warranty. I would recommend to replace hard drive even if it works because its lifetime can rapidly decrease after the power supply problem.

Good luck!
Mark O'BrienDispatch Software Support and Server AdministrationAuthor Commented:
!WOW!  I am greatly impressed  by all the excellent, scientific, and helpful advice.  I just dont know who to give points to now.
I bought a new pwr supply and luck must have been on my side.  The pc is working and stable.  Of course, nobody can know if any of the smaller circuits on the board are blown or not.  That concerns me.  So does the statement about the HD.  Guess I better keep my credit card close at hand.
I heartily agree with nimatejic's comment: "Some people save mony on PSU's, but this can give you even more expenses. I strongly recommend a PSU from Corsair, Thermaltake, Enermax or similar manufacturers."  I have usually purchased Antec's pwr supplys just b/c they are everywhere and usually inexpensive.  I am going to switch to another brand as listed above, tho, b/c I have had historically bad experiences with Antec.  I recommend that buyers beware of Antec, in my opinion.
I will never skimp on pwr supplys again.  Im going to get really good ones from now on.
Thank you all, very much for the help.

Mark O'BrienDispatch Software Support and Server AdministrationAuthor Commented:
Increasing point value
Mark O'BrienDispatch Software Support and Server AdministrationAuthor Commented:
If I could, I would award each of you 500 points.

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