On 08/18/2010 02:34 AM, Robert G. (Doc) Savage wrote: > > On Wed, 2010-08-18 at 00:27 -0500, Thomas Cameron 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. >> >> Say those systems have been running for over a year, but lately they've >> been really flaky. Random lockups, sometimes they boot with garbage >> characters on the screen instead of the normal OS boot, sometimes they >> hang at various parts of the boot sequence, spontaneous reboots when >> kickstarting. >> >> Say the Antec web site says I need more like a 350w power supply, and I >> read somewhere that PSUs tend to age and get less efficient over time, >> so I am guessing that I've been starving these things for juice for >> weeks or maybe months. >> >> Hypothetically, could I have actually damaged these systems if the PSU >> was under-powered? Or would a new, higher powered PSU fix the problems >> I've seen? >> >> I would guess that too much juice might hurt the systems, but would too >> little actually damage anything? >> >> I know it's not thermal, they're in a very cold room with dedicated HVAC >> and the airflow is great. >> >> Hoping someone who knows more about electronics can chime in. > > Thomas, > > Your suspicions about cheap-o PSUs may be well-founded. A power supply's > Achilles heel is often the electrolytic capacitors used to absorb and > filter out high frequency components on its main power output lines. > There are a lot of square-wave-to-sine-wave conversion operations that > take place in modern power supplies. > > When electrolytic capacitors (the big ones that look like beer cans) age > the paste-like electrolyte inside begins to dry out. The heat inside a > PSU accelerates this aging process. The telltale sign is AC ripple on > the +5V and +12V outputs. You can see this on an oscilloscope and > measure it with an inexpensive voltmeter set to read AC volts. > > When 120VAC at 60Hz leaks onto DC power rails, the instantaneous voltage > (the sum of AC and DC voltages) applied to delicate logic may be many > times higher than the nominal low DC voltage that should be there. This > can easily confuse circuitry trying to measure the electrical charge > stored in a memory cell that represents a 0 or 1 bit. > > I've seen this cause spontaneous reboots, system freezes, and all sorts > of seemingly random behavior. It's quite common in home PCs whose PSUs > have been inhaling dust and pet fur for 4-5 years. It's less common in > data centers, but equipment close to the floor can still accumulate a > lot of dirt. Lower temps in a data center may slow heat-related > deterioration, but cheap PSUs will still age faster than well designed > units with quality parts. > > BTW, this problem is not confined to PSUs. You've probably read about > motherboards with bad capacitors. A few years ago there was a major > scandal involving defective capacitors sold to many top tier motherboard > manufacturers. Tens of thousands of motherboards made with those bad > parts are causing headaches for sysadmins today. > > If you have any doubts about a particular machine, go ahead and replace > its power suppply with a known good one. If you can afford it and can > find one that fits, you might try replacing a cheap-o PSU with one from > a vendor like PC Power& Cooling. > > Good luck. > > --Doc Savage > Fairview Heights, IL > Thanks Doc. We've already replaced all of them with Ensoniq units. I was really more worried about whether I had damaged the boards. -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
