Why PSUs Fail

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Lots of things can go wrong and cause a power supply failure. In this article, we take a look at the most common. We're pretty sure at least one of them will surprise you.

Why PSUs Fail : Read more
 

chaz_music

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Great article. I used to design power supplies for industry, and your comments are right on. I always thought of failure modes caused by different factors: design errors, manufacturing errors, transport (mechanical usually), and end user handling/installation. For instance, cracked ceramic caps can result in both mechanical stress from the soldering process and high vibration during transport.

The bugs found are also very real! I have found insects and animals before inside of products. When I was in college I would make extra money repairing arcade games. One game had a CRT monitor that was blank, and inside I found a very well cooked mouse with one front paw on the HV connection going to the monitor, and his back foot was on kine ground (HV ground). He had destroyed the monitor because his feet had put HV everywhere. But as Edison had said of his mousing days, they had "left this worldly sphere".

Another point is on UPS systems. Most of the cheaper ones are "standby" or line interactive types. The only UPS system that continuously clean the power are double conversion and are more expensive and have lower efficiency. For this reason, the standby types are often marketed as green power efficient types, which they are, but only because they act only when the power glitches. If you truly have bad power in your area, you need a double conversion type to protect your electronics.

Appreciate the good articles - Charles.
 

turkey3_scratch

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Wonderful article; to sum it up, the manufacturing process and good soldering seem to be the most important thing for high end PSUs. Hopefully this will help people to realize electrolytic capacitors are not quite as relevant for high end PSUs.
 

Glock24

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I had the bad luck of having 3 Seasonic PSUs malfunctioning after around 2 months of use. The model was S12II-430.

Those were my choice for systems I built myself and for other people, and some home servers. They had a good track record, with no failures and some of them in service for more than 4 years. In total I must have bought over 10 units of that particular model.

The ones that failed were purchased between 2016 and 2017. Maybe a bad batch? Defective components? Shipping damage? Don't know, but Seasonic replaced them under warranty.

The failure was random shutdowns or reboots.
 

Glock24

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I've never found bugs on PSUs, but once found ants in (poorly maintained) laptops.

What I've found a couple of times inside dead PSUs are (fried) geckos.
 
It may be difficult for some but keeping your PC apart from high draw appliences can help. While you have a UPS and a surge protector other surges on the same line can affect the quality of the surge protector over time and eventually cause a protection failure. A light will go out. That may not be the unit's power light. It may be a protection indicator.

Please correct me.
 

studmoose

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The worst thing you can do to a computer or laptop:

1) Have it plugged into street power, without any power conditioning or suppression.
2) Have it plugged in without a top quality battery backup that remediates #1.
3) Routinely turning the units off.

I've been an IT officer for 30 years, and it is rare that systems are turned off, whether they are rack-mounted servers, midrange or mainframe systems. The field engineers and customer engineers stay on-site, as the power on process is the most prone for failure. Their vehicles are stocked with the most failure prone parts to minimize downtime in the event a part needs to be swapped out.

My one home computer is a Dell Dimension 8100, which is on it's second power supply, since it was built in 2001. My work laptops are never turned off, unless I am transporting them or going on a vacation. My current one has been powered up for almost a year now. I leave my systems up, through all but the heaviest of thunderstorms, and even then, some hit when I am away from the house, while they are powered on and idle. Sure, it burns more power, but component failure are minimal. The PSU failure and a HDD grinding after 10 years, were the only two issues with the Dell in 16.75 years. One Thinkpad, 8 years ago, had a HDD failure after 2.5 years.

Repeated power-offs and ons, cause slight surges and create rapid heat expansion on previously cooled CPU, mainboard, storage and PSU. The momentary power spike and the thermal expansions and contractions between power cycles is what really kills a system. My next system will be a higher efficiency SFF, which also will remain powered on for long durations.

If you want to destroy your battery in a laptop, keep unplugging and plugging it back in. Each time you do that, it counts as a charge. To prevent laptop batteries from catching fire, there is counter circuitry that will slowly inop your battery when it gets close to the count limit. This is their best way of determining when a battery might fail and disable it beforehand. Our laptop batteries routinely last over 3-4 years, whereas those who plug and unplug frequently might see a 1.5-2 year lifespan.
 

bmwman91

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Good wrap up of the issues. I have seen, in both PSUs and GPUs, FET failures in synchronous buck converters very often. In almost all cases, the FETS bear markings of some mystery company overseas which is probably knocking-off parts from ST/ON/IR/etc. The combination of poor timings leading to too much shoot-through, plus higher RDS-On from cheap fabbing, seem to lead to a lot of high-side FET failures which allow the full source rail voltage to be applied downstream (the failures are frequently internal shorts).

At this point, I usually only buy PSUs that I have seen the guts of beforehand so I can see who manufactured the components.
 

bit_user

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In that case, it's not that turning them on causes disproportionate wear, but it's:

    ■ When self-test occurs.
    ■ When the system might be under higher-than-normal stress, hence marginal components (that would eventually fail anyway) are more likely to fail.
    ■ Starting mechanical components from a dead stop places all sorts of stresses, especially when you don't do it regularly. (see: https://en.wikipedia.org/wiki/Stiction#Hard_disk_drives )



IMO, this verges into the realm of superstition.

I typically use sleep, rather than power-off, but that's mostly because I dislike waiting for shutdown & bootup. Systems I don't use daily get turned off (except I often leave them plugged in & power supplies' hard switches turned on). And guess what? I don't have component failures, either. I attribute that mostly to buying quality components and a good UPS.
 

Karadjgne

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It would be nice if psus included actual knowledge in their booklets. For me, the biggest killer of the psu was the ignorance of the end user, caused by lack of info from the manufacturer. Take the active pfc (since UPS were mentioned) in my Evga G2. Works like a champ, great psu. Doesn't work on my Minuteman Pro 700 UPS. Active pfc does not like square sinewaves. UPS works great on my old Seasonic M12-II, plenty of time for shutdowns, but on the Evga if power goes out, boom, so does the pc. The UPS needs to be the expensive 'pure sinewave' kind. Might have been nice if the psu manufacturer included that tidbit of info. Brown outs aren't good for a psu.
 

Karadjgne

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Yes. I've called it a square sine wave for so long, talking to ppl who can't picture it. Even equated it to the crenelations of a castle once. Sinus rhythm = 'you know, the Chevy Heartbeat'...
 

Karadjgne

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Square waves are the easiest transformation of DC to AC voltage, it's 2x set amplitudes, like on/off in a constant rhythm. Pure sinewaves are a lot harder as they are constantly variable with only the peaks being set.
 

zthomas

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Two AM I awoke to what sounded like a bullet whizzing by.. in fact it was my power supply that blew up.. My last upgrade about six months before I added a 1200 watt unit.. my thinking I was going to run a couple video cards..
 

KidHorn

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PSUs are the biggest point of failure. And also the component most likely to be DOA. That's why I always have a spare PSU. Nothing is worse than putting together a system and you turn on the power and get nothing. Is the PSU bad? Maybe. Switch to one that you know works and see. Otherwise, it could be anything.
 

turkey3_scratch

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Data on this or just speculation? I'd assume GPUs probably to be the most failure-prone components, the maybe motherboards and hard drives.
 


Can you provide some product names/models that offer double conversion?

 

Karadjgne

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Actually turkey, you could assume kidhorn is correct. Taken worldwide, with the sheer amount of knockoffs and $5 psus that come in cases, low end OEMs and all the other trash, the psu is more than likely the most common failure point. Mobo's might look to fail more often, but there's really not that many manufacturers, same for ram and even hdds. Psu's, however, seem to be made by anyone with a soldering iron.
 

turkey3_scratch

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I just don't like making assumptions like this in general. You may be correct but I really don't know, maybe we'd be surprised.

Remember that a low quality PSU will affect the lifespan of all the other components, too. So if we take that into account it may not be so clear cut.
 

bit_user

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A keyword you'll see more often is "online".

https://www.newegg.com/Product/Product.aspx?Item=N82E16842107133
https://www.newegg.com/Product/Product.aspx?Item=N82E16842111098
https://www.newegg.com/Product/Product.aspx?Item=2FT-000X-002F6

You can also buy power filtration products (often sold towards medical & industrial markets) that don't contain a battery backup.

https://www.tripplite.com/products/power-conditioners~23
https://www.tripplite.com/isolator-series-120v-1800w-ul60601-1-medical-grade-isolation-transformer-6-hospital-grade-outlets~IS1800HG


I once had a CRT monitor that was incredibly sensitive to AC interference. I got the idea to plug it into my Panamax home theater power conditioner and it worked beautifully. Later, I moved it over to an APC Smart-UPS (the old kind, with pure sine wave output) and it worked nearly as well.

http://www.panamax.com/


Funny story: I was curious just how bad the harmonics were in the output of another APC UPS I had, which featured "stepped sine wave approximation". A friend hooked it up to an oscilloscope and we found that the waveform on battery power was actually cleaner than when the UPS was on AC power, at the office building where we worked.

And that's the last I worried about the "stepped sine wave approximation", until I started reading about PFC PSUs and how particular they are.
 

Karadjgne

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I had a pretty new gell cell in my UPS, according to the monitoring it was a-ok good to go. Then a couple of reboots later and now I'm wondering what's wrong. Went through the entire pc, physically checked everything software, hardware, driver, everything. Spent hours on it. Come to figure out it was my psu. That APFC just doesn't work on square wave, so when power was jerked around, I got nothing but a decent surge protection.

Now I'm looking at $150+ UPS thats pure sine, downside is it only lasts for minutes at decent loads. Older square wave 550/600 would last for 1/2 hr...
 
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