I have an APC Back-UPS RS 550G which I've been using in my home office for about a year. It saw me through a few power outages for which I was quite glad. However, I've lost quite a bit of time to an peculiarly high incidence of device failure over the course of the year.

I just read a few 'before the fact' questions about the quality of the power output from inexpensive UPS units. This is an 'after the fact' question: How likely is it my UPS is the culprit?

  • The motherboard on my computer failed
  • The GPU card failed
  • The motherboard on the substitute computer failed
  • Two 240/120V ac transformers died in succession (but not the dc transformer plugged into them or the device it powered)
  • My router/adsl modem and its transformer both died

My led monitors are the only devices which have been plugged into this ups for more than a day and not yet failed.

The UPS is plugged into a separate surge protector, though the surge protector is a few years old and probably should be replaced. The two computers were both still under warranty and the service technician just replaced the motherboards without any further diagnostics. Currently they are both working.

I've moved everything but the computer and the monitors off the UPS. How seriously should I consider replacing it (with a pure-sine model)? Should I have the power supplies on my computers checked or replaced? (the substitute uses a laptop ac adaptor.) What would you do if it happened to you?

Updated question: If something with the power supply is suspect, whether it's from the UPS or lightening or something else, is it conceivable that the motherboards would have been damaged and not the computers' power supplies? Or is it likely that the PSUs were also damaged and therefore that these machines are 'at risk?'

  • I think this is already answered in the linked (and related) questions: It may or may not be the reason, which depends entirely on the designs of the psus involved. – PlasmaHH May 27 '15 at 10:43
  • Is the line-in to the modem also protected? I have seen equipment protected by surge protectors and UPS devices damaged via unprotected phone lines, cable or Ethernet. Power surges, especially lightening, can do serious damage to equipment even if it is not directly connected to it. I've had lightening come in through a phone line take out the modem, the broadband router, motherboard, memory and monitor. All those devices were plugged into UPS/Surge power protection, but the phone line wasn't. – CharlieRB May 27 '15 at 14:07
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    It really sounds to me like you lost all this equipment due to lightning damage. In a serious storm with some lightning pickup on the wires into your home office there is very little that most UPS's can do to help. The MOVs in surge protected UPS sockets and in pathetic surge protector outlet strips can maybe help some with the "easy" lightning surges but if a serious spike comes through it can cause the type of damage you saw. I had a case once with losing a keyboard, one motherboard, ethernet hub, one motherboard and one monitor on a three computer setup. There was no logically (continued) – Michael Karas May 27 '15 at 14:15
  • (continued from above) obvious reason for why it took out what it did as the failed electronics was spread across three systems. Also hard to know if some of the other equipment in that case had latent damage that was not immediately observable. I can comment that one of the computers in that case had its motherboard chipset component fail inside the chip some five years later - it could have been related ? ! ? – Michael Karas May 27 '15 at 14:20
  • @MichaelKaras that is interesting that the damage might not be immediately observable. We have had more lightning storms here than usual, but there was no immediate damage during any of them. When possible, I usually turn of the UPS and just unplug everything before the storm. – Aryeh Leib Taurog May 27 '15 at 16:36

I can give you a definitive answer to the question in title. However, you have an unusual situation, and it's only possible to speculate as to what else it could be.

Could your non-pure sine wave UPS be responsible for the damage?

The waveform from the UPS cannot cause damage. If your computer has an active PFC power supply, a cheap non-sine wave UPS can lead to the equipment shutting down at the time of the switch-over, but not damage. If the UPS worked fine in keeping things powered up during outages, you don't have to worry about the waveform issue or need an expensive pure sine wave UPS.

Also consider that some of what failed was never plugged into the UPS.

Could the problem be due to power surges?

Cheap surge protectors that use MOVs are single-use protection; the MOVs sacrifice themselves and tend to burn out in order to protect your equipment. After they have done that once, the protection is usually lost.

That said, power surges short of a lightning strike tend to be self-limiting. For example, if the computer's power supply is not able to handle the surge, it is likely to fail before the components it powers are damaged. If you were to sustain surge damage beyond the power supply, it is likely that most components would fail simultaneously. It doesn't sound like that has been your experience.

If your utility power is horrendous, you might benefit from the type of UPS that is always active. Rather than switching over to battery when the power goes out, you always run from the battery and the UPS keeps it charged. That isolates your equipment from the utility power.

However, if the utility power isn't adequately protected from lightning, even that might not be enough to protect against a serious lightning strike. In fact, there isn't much that will, short of unplugging things. But again, the failure pattern you describe doesn't sound like lightning or surges.

Common Denominators

The multiple failures aren't from the UPS, but they sure are unusual. My first reaction might be that the failures were misdiagnosed and some of the early replacements might not have been necessary. If the problem cleared up after replacement and some time later there was a new problem, that would indicate that this isn't the case. Although..., the process of servicing the computer might have included blowing it out or other actions that temporarily solved a different problem, like heat.

If the computer failures are all caused by a single underlying problem, there are only a few common denominators. One is the internal power supply, another is heat.

The only way I could envision the power supply damaging many different components would be if the voltages it is putting out are too high. I have never personally seen a power supply do that, but it's something you could check with a voltmeter.

If the inside of the computer is getting too hot, or heat isn't being dissipated you could get failures, although some components tend to shut down before they are destroyed. Signs to look for would be air vents blocked with dust, or exhaust fans caked with dust. You could also get excessive heat if the computer is in a confined space.

Multiple component failures might be due to bad computer build quality. Your computer could have been made on a Friday out of all marginal parts. Except you mention two AC transformers, a modem, and its power pack all failing, also. Unless you buy only cheap stuff from disreputable merchants, it doesn't seem likely that everything would fail, and do so in a short time frame.

Coming full circle

Which points back to a power problem, perhaps successive power surges on your utility line. Each surge might weaken various items; not enough to cause immediate failure but failure after varying numbers of similar hits. You could get a condition like this if you are next to a commercial or industrial facility with heavy equipment cycling on and off. If your only protection is old surge protectors with fried MOVs, you might not have any protection. Of course, replacing those with other MOV-based surge protectors puts you back in the same situation after the next surge. The computer component failures don't sound like a typical surge problem, as I described earlier, but your whole situation is unusual, so it's hard to rule anything out.

It might be worth talking to your power company. They may be able to put monitoring equipment on the line temporarily to see if there is a problem.

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." Arthur Conan Doyle

Of course, just because something is improbable, it doesn't mean it can't happen. Somewhere in the world, somebody will be the one person who experiences every component failing in quick succession. You might be that person. Or at least there might be more than one underlying problem.

  • Would a power surge likely have damaged the PSU as well? If so, would there be any way to detect it, and would the replacement boards also be at risk? I don't know about misdiagnosis, but replacing the motherboard twice turned a brick back into a computer. Heat may indeed be a factor, because they are small units and possibly somewhat under-ventilated, but they are otherwise ordinary desktops from a major manufacturer. If they had such extreme problems, I think I would have heard about it. Also as you pointed out that wouldn't explain the other failures. – Aryeh Leib Taurog Jun 4 '15 at 9:37
  • PSUs generally either work or don't; I've never seen or heard of one failing in a way where it outputs the wrong voltage. It would also likely be the first thing to fail. I've never seen a case where a surge fried a bunch of internal parts but left the PSU unscathed. Unless you are in an area with constant surges, you wouldn't likely see many devices and components failing at different times. More likely explanation: the repair shop is using low quality, refurbished parts rather than new parts, and/or doing a poor job with thermal paste. But that still doesn't explain the other devices. – fixer1234 Jun 4 '15 at 13:54

Another thought here: I don't see the PC's power supply listed as something that failed.

It would be hard to fry the components in the PC without first frying the power supply. Thus perhaps the real problem is the PC's power supply--it's sometimes throwing spikes. It's throwing them in both directions, though--some of the high voltage from the conversion stage is going back up the supply line.

  • Burning out two AC stepdown transformers would mean a 240 watt PSU is throwing a lot of energy back into the line. However, my next guess would have been EMP from living too close to a nuclear test range, so I'm not going to second guess your idea. :-) – fixer1234 May 28 '15 at 21:15
  • @fixer1234 I'm sure it couldn't blow an actual transformer--but what about control electronics? – Loren Pechtel May 29 '15 at 22:13

I'd like to add to this conversation a bit late. First off, I am no PC expert and no electrical expert. But I can tell you this, a few years back I bought a moderate to small Cyberware UPS simply for items like my home phone, my magic jack, router, a switch, a light & my ATT router. After about 6 months - each of those items failed. First it was the magic jack, then the router, then the phone (I had the main base attached - satellite phones were seemingly undamaged), the light from 1960 is the only thing that survived. I figured, well, maybe I wasn't supposed to do that. Maybe this was my fault. I posted a review on Newegg where it had been bought, received a reply online from the company to call them - did so & never heard back. Chalked it up as I probably shouldn't have done that, lesson learned. Leave the UPS to the PC's and call it a day.

Fast forward to November of 2016. I have another Cyberpower UPS, not the largest model, but much bigger than the other one that failed. Lately, had issues with the PC, thought it was some kind of update issue that didn't install correctly, but also realized PC had been around for many years and perhaps other things were going. Finally had to simply restore system to an earlier time. Then a few days later, realized the TV tuner card was not working. AT THE EXACT SAME TIME, my HD Silicondust (a TV tuner that is not a card you put into the system) had also failed. What did they have in common? Plugged into the same UPS. So, this time, I removed UPS and plugged all items into a surge protector and what do you know...PC booted up beautifully (it had been acting sluggish & kind of weirded out) AND the TV tuner card inside suddenly decided to work again (which I had tried it one more time before I powered down). That PC is working for now, but may not last much longer - I can't say exactly what happened. The HD Silicondust tuner is - well - dust. The antenna hooked into the Silicondust tuner also seems to be fried but I have not had a chance to work through all of that just yet. For now, I can't even speak for the external drives that were also plugged in - they may or may not be fried. It also damaged the PC speaker system that was plugged in. It's also worth noting, the same four plug outlet in the wall has ANOTHER UPS hooked in, with another system - nothing on that one is weird, broken, acting odd, etc. The two are not connected to each other EXCEPT by the direct line outlet (which is not the same outlet that the other Cyberpower UPS was plugged into that failed back in 2013 or so).

I had quite a bit of electrical work done back in 2012. Had a whole home surge protector installed. Had a ton of outlets installed as direct line outlets to all the various home theater electronics and PC's. We have had no rain, no storms in this area - one can never really speak about electrical surges and the like. It is possible something happened when I was not there or that I was unaware of. But no other device or PC system in the house is acting odd or having issues.

I know that with my lack of experience and knowledge, this could easily be some other problem. But the fact that TWO Cyberpower UPS have been the link between systematic fails of multiple devices - I have to assume a UPS can indeed, somehow, damage the items plugged into them. Neither of these UPS were Sine-Wave. But it is very odd that - seemingly - so far, the power supply, the motherboard are acting normal - but the TV card tuner was not working until I removed the PC from the UPS. Go figure.


APC UPSes destroy power supplies.

SmartUPS 2200 when batteries go flat start sometimes to do fast on/off cycles. In a datacenter you won't even see or hear that.

That UPS destroyed HP DL360 G5 and Brocade VDX6700 power supplies. HP server seems to have problems with its power subsystems still after replacing the broken power supply. Weird.

APC UPSes test batteries and when battery is on red then it will cut power to its devices. Typically battery test is done once a week.

APS is still not the poorest UPS there is. One maybe Italian made(?) cuts automatically power to its devices when batteries go flat. Immediately. But it beeps while doing that. Clever.

Basically going to replace all APC UPS devices with another brand.

  • We were using around 30 APC online model larger UPSes. Last week one APC UPS had its last dying stuggle (yes, the lights have been red for months) .. this time the USP took local group fuse (2-phase, for ~3.5kW) and the whole groups fuse (3-phase for 15kW). nice. But currently no power supply damages. Oh, running a data center with capacity of 2000+ U. – Kaarlo Rotten Apr 2 '20 at 10:23

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