Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why do power supply units "blow"

  1. Oct 17, 2015 #1
    I just recently finished a new computer build for $280, or so I thought. I did it reluctantly. I was hoping to hold on to my old Core2Duo I built back in 2007 until 2022 when they stopped supporting Windows 8. In fact, I probably would have pushed it even until they stopped supporting Windows 10 with the free upgrade :smile:

    However, while I'm able to milk all my other components for all they're worth, my PSU's always seem to give out on me every 2-3 years. The last one supposedly shorted out my motherboard when it took a dive which is why I had to assemble a new build.

    Now my new build is making a high pitched-whine from the PSU. I don't even have to turn the computer on, it just sits there and whines turned off. I have to turn the PSU itself off to stop the noise. So I had to order a new $40 Corsair which pushed my new build over $300. That made me furious :mad:

    I know the PSU is a mini-transformer and, as such, seems to be more prone to failure than perhaps most of the other components of the build, but what is it actually that keeps failing? What is the limiting factor? I read that the high pitched squeal that typically signals the death throws of a power supply unit are burned-out capacitors. Is this right?
  2. jcsd
  3. Oct 17, 2015 #2


    User Avatar
    Science Advisor

    The primary factor is underrated cheap components in the areas of the supply with the most stress. Capacitors are usually the primary culprit because cheap ones are build with the thinnest layers and lowest quality materials to reduce cost while having the highest value of capacitance at the rated voltage. This means the ESR is high causing heat generation from the high peak currents normally seen in switcher type power supplies. Cheap fans with small internal heat sinks on hot components also are an important factor in killing electronic parts.

    power supply failure
  4. Oct 17, 2015 #3
    Thanks for the white paper. Those pesky Zinc whiskers, I should have guessed :oldgrumpy:
  5. Oct 17, 2015 #4


    User Avatar
    Science Advisor

    I repaired stereos as a kid. Roach Infestation was pretty high on the list of root causes then. Zinc whiskers and poor solder joints in general was not a big deal then because we used lead for solder and wiring. Today it's a mess, RoHS is a nightmare for high-reliability.

  6. Oct 17, 2015 #5
    Jeez, I don't even know why I'm telling you this, it's embarrassing, but it seems related to your comment, so being a sucker for cognitive association, here goes:

    When I was a kid the late 80's I met this tourist girl in Hawaii and we had a week-long fling. Most of the tourists just come and go and you don't hear from them again, but a few make the attempt to stay in contact. This girl was one of them. Anyway, she lived in the hinterlands of Puyallup, Washington, and invited me to come down and visit her for a week (and pay for the ticket). Well, I couldn't refuse, good excuse to get out of the hotbox of Waikiki for a spell.

    So I received my ticket and boarded the plane with my 80's "fanny pack" and my 80's "boom box" (we didn't have iPods back then). I'm sure you've worked on a few boom boxes. So I arrived in Washington and had a great week. This girl was living at her parents house at the time and we all got along really well, with the partial exception of her brother, who seemed to eye me suspiciously from the get go o_O

    In any case, after a really fun week in Washington State, I visited all the cool landmarks and even hiked up Mount Rainier, I'm back in Hawaii and get this troubling phone call from the girl. She tells me that cockroaches have infested their entire property and they can't get rid of them. Turns out there was a population of roaches that infested my boom box that "stowed-away" for the trip. If you've ever lived in Hawaii or any tropical climate you know that cockroaches are everywhere. However, in rural Puyallup at the time no one had ever seen one. So it must have come as something of a shock.

    They infested the entire house and during the winter they nested around the hot water heaters and radiator units.

    It took about 3 years to finally get rid of them. I actually kept up a relationship with this girl and went back to visit a few times more despite the fact. However, forever after that and until we broke up, I was designated as the "bug man" by her brother, who never eventually warmed to me (obviously).

    So there you have it, my cockroaches served as a successful "viral vector" because they didn't kill their host, my boom box. To prove this I can tell you that I was cranking the George Michael on that baby all night long as we were making love in her attic. And there was no short to be found :biggrin:
  7. Oct 24, 2015 #6


    User Avatar
    Gold Member

    The main reason power supply units blow after 2 or 3 years is because that's how long it takes the dust buildup inside to cause it to overheat and self destruct.

    You need to apply compressed air to clean the dust out of the supply.

    The next major cause is fan failure causing overheating, and the next is bad capacitors in a cheap supply.

    I think dust buildup is by far the most common.
  8. Oct 24, 2015 #7
    That looks like a pretty good assessment. Every once in a while when I cleaned out my computer I would send some compressed air through the outside of the PSU assembly. But I was always not sure how effective this was. Same thing with the aftermarket CPU fan. It seems as compressed air can only do so much. There always seems to be so much "gunk" left behind. I got tired of going through the fan blades with a q-tip.

    Kind of hard to check that--PSU fans are usually pretty quiet anyways. Besides, how long could the PSU last once the fan went out? My guess would be not that long and you wouldn't know it soon enough to prevent it.

    That's probably what did me in. It was a cheap 430W Thermaltake from a small local shop. And I'm guessing that the high-pitched squeal gives away a capacitor problem?

    In any case, I got the new 500W Corsair in there right now and it's quiet as can be. It's so quiet that, when I fired it up the first time, I thought it was DOA because nothing happened. But then I saw the MB LED on. So I thought, this is great. Corsair PSU's are pretty cheap, too, though, $44 or $24 after a $20 rebate (if I get it). Anyway, I hope it lasts. I'll take your advice and try to blow the dust out every few months.
  9. Oct 25, 2015 #8


    User Avatar
    Science Advisor
    Gold Member

    A big factor is variable power supply to the PSU. The electric power grid is not immune to voltage and frequency variance. This stresses your PSU over time. The other factors mentioned play a role, but variability in the grid power supply is still a big factor. It depends where you live, not all legs of the grid are the same. Using modulaters [like a battery backup with surge protection] will help.
  10. Nov 7, 2015 #9


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The life expectancy of an electrolytic capacitor is very temperature sensitive. If you run them close to their Max temperature some only last a few thousand hours! It's surprising how few electronic engineers know this. Many famous companies have had whole production batches of their products fail within warranty or just out of warranty. It's so common that some people sell kits of replacement capacitors o eBay. I've had to replace the caps in a PVR, Sat receiver and LCD monitor in the past two years.
  11. Nov 27, 2015 #10
    When i picked a PSU for my primary it was grossly oversized for the application, 850w where half that capacity was really needed. Paid more then for sure. But said unit has racked up well in excess of 65,000 hours of service. Sees downtime a few times a year for cleaning with the rest of the box, has always been supplied through a filter/ups. I took the cover off once well after warranty period had expired to remove some of the larger dust bunnies and the few insects who had met their end inside the case.
  12. Nov 27, 2015 #11


    User Avatar
    Gold Member


    My son buys failed monitors and TV's and the replacement capacitor kits. I get to do the soldering. (at least I don't have to disassemble and reassemble them)

    It isn't as significant as it was 5 years ago. But a few people made decent money selling the kits and others selling repaired devices.
    It will always be an issue in that many component manufacturers are going to cut corners to grab a little more profit, and consumer products design by ODM's will always try to squeeze out the last 0.1 cents. Low ESR capacitors in switching supplies are a primary cost cutting target by both designers and purchasing agents.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Why do power supply units "blow"
  1. Power supply (Replies: 3)