Somewhat OT - can underpowered power supplies damage a system?

James Mckenzie jjmckenzie51 at
Wed Aug 18 16:08:07 UTC 2010

Kwan Lowe <kwan at> wrote:
>Sent: Aug 18, 2010 8:37 AM
>To: Community support for Fedora users <users at>
>Subject: Re: Somewhat OT - can underpowered power supplies damage a system?
>On Wed, Aug 18, 2010 at 1:27 AM, Thomas Cameron
><thomas.cameron at> wrote:
>> Say, hypothetically, I have 8 identical Intel DG45ID motherboard-based
>> system with 8GB memory and a single drive with a cheap-o generic 300w
>> power supply.  All running Linux, so sorta on-topic.
>Wiser folks than me have chimed in, but I wanted to add an anecdote...
>I used to use bargain power supplies on all my systems. These are the
>400W that come with the $30 cases I used. On my cluster of about 10
>nodes with 2 drives each, I was sending back a drive every month.
>Failure rate was about 5% every month, in other words.  Since
>upgrading all my power supplies to warrantied, name brand units
>(mostly Antec, but others also), I have had 2 failures in 2 years.
I had a system saved by one of those bargain power supplies when the transformer on the pole had a primary-secondary short.  Almost killed the UPS, but the power supply transformer shorted out blowing the fuse in a most spectacular manner (the wire splattered on the glass, cracking it.)  When I took it to a local shop, in Korea, they plugged it in after replacing the fuse.  The fuse arced over...  I got a new supply out of the deal and they did not believe what happened to it.

Maybe a brand name's power supply would have not shorted out, but then the mobo, drives and everything else would have received a 6000 volt shock.  And yes, the UPS was brand name (highly rated BTW) but the short duration was so short that the system did not shut down.

So, $30 PSU or untold $ worth of data?  I'll take the former.

Lastly, check the waveform output of your PSU.  This will take an o-scope.  If the line is not flat, or nearly so, replace the PSU.  I've seen +5v with a chopped waveform that had up to +12v spikes.  That will do in just about everything (even the mobo voltage clamping chip would burn skin on contact [do mobos have these anymore?] and the drives were acting real funny.)  Blowing drives is a major indicator that the PSU is not up to snuff (power rating or no power rating.)

Also, given the current loads from Pentium iCore processors, it would not hurt to drop a 400W continuous power rating PSU into your system, especially if you are running several hard drives and a powerful graphics card.

James McKenzie

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