On Mon, 2011-11-07 at 22:22 -0500, Chris Knadle wrote: > On Monday, November 07, 2011 07:03:50 PM, Adam wrote: > ... > > The first time this happened was two weeks ago, and somehow after a > > few hours the problem, whatever it was, "fixed" itself. This past > > weekend I powered it down for the first time since then, and it did > > not power up at all. During that time, I used my DMM to measure one > > of the peripheral power connectors (the kind that would power a PATA > > drive), and discovered that when AC is applied, the +12V line rises > > within about half a second to about 0.67V and stays there. When AC > > is removed, that voltage gradually drops to zero as the LED flashing > > slows down. When the +12V line is steady at about 0.67V, the +5V > > line is steady at about 0.27V. > ... > > Obviously something is very wrong here. My question here is, is it > > more likely that the problem is the power supply or the > > motherboard? > > I'd say this is got to be a power supply problem. I've recently found out > some very interesting things about power supplies, which I'll share. [This > came up on the LIMARC "Tech Net" a few weeks ago, which had a power supply > expert on the radio that explained the follow details.] > > First, non-air capacitors have a limited lifetime. Here's where it gets > really interesting, though: a typical lifetime rating is around 2,000 hours. > Yes, you read that right: in 24/7 use terms that's about three months. The > reason is that over time, non-air capacitors slowly break down such that the > voltage rating slowly lowers. When the voltage rating finally lowers to the > voltage that is in use, it arcs over and the capacitor becomes a dead short. >
The problem with Adam's PC may indeed be the PSU. But regarding the lifetime of capacitors, here is a contrary view on PSU life from some non-experts on the Anandtech Power-supplies forum: It is from the recent thread "How long does a PS actually last?" http://forums.anandtech.com/showthread.php?t=2201228 Here is one comment from that thread: "I've seen computers from 1990 still running fine. That would be a 20 year old power supply." There are other similar comments on that thread. I own two year 2000 Dell PC's each of which has seen over five years of 8-10 hours per day, 6-7 days per week of use with no problems. Adam: I have two spare PSU's. One is a 250 watt FSP. The other is a 420 watt Thermaltake. Since MHVLUG was nice to me several years ago at the swap meet, I'm willing to lend you one of those PSU's if you want to try a quick substitution. _______________________________________________ Mid-Hudson Valley Linux Users Group http://mhvlug.org http://mhvlug.org/cgi-bin/mailman/listinfo/mhvlug Upcoming Meetings (6pm - 8pm) MHVLS Auditorium Dec 7 - An Intro to Chef Jan 4 - Recovering the Brownfield: Revitalizing Open Source Projects Feb 1 - Home Networking Made Simple with Amahi Home Server
