sometimes, things are simpler than they seem

[Lex]

I had a computer that was freezing up, (locking up), occasionally random rebooting itself. It was quite annoying, with rarely a session without freezing up.

Finally, I decided to remove the computer, took outside and blew all the dust and crud out of it with an airhose. I also ran Ad aware and looked for anything problematic, and ran a virus scan. The net result was, after all this was done, and I'd cleaned some stuff up, my computer ran like a wild deer, no freezes, no hits, no runs, no errors. Sometimes, things are just that easy. Go figure. I thought maybe it was a bad power supply, as I have had problems with those.

Unfortunately, since I did not perform the operations one at a time, I cannot say for sure what fixed it that I did, but something sure did.

[maximumshow]

One of the simplest and quickest things to check for are bad/blown capacitors on the motherboard. As a computer tech I see it ALL the time. If any of the X's on th tops of the caps are domed outward, or have brown and white crystals on them, the caps are shot. From my experience, nearly half of all systems that keep rebooting randomly have bad caps.

[JonMarsh]

Yeah, that's starting to be a real epidemic the last two years on less expensive MoBos... such as Dell Enterprise desktops.

The problem is that once the caps start going, the VRD regulator can't handle the big current di/dt when a big block of code kicks in, and the programmed VRD output voltage drops out of reg, sometimes way out of reg.

I work in this business (on the power semiconductor side), and for our reference designs, we get sample kits from many of the big cap manufactureres. By sample kits, I mean big shelf storage units with every part they make in the relevant series.

The problem is, due to the cost pressures, even the guys that make some of the best caps have series designed a series for a "defined" lifetime at 100C, generally 1000 hours, which is not all that long- I call them the "one year PC" caps. Three hours a day.

You probably don't realize it, but the VRD regulator componenets are probably the hottest running parts of your computer, and it's' not unusual for a VRD design running at full thermal power (think 3D games or MPEG encoding, for example), to be sitting at 100C temps on the PCB. The UL limit is about 105 or 110, and everyone designs a system JUST good enough to stay under that limit.

In light use duty cycle, those cheap MoBos will hold up for a few years, but for a hardcore gamer or video nut, or CAD type, they'll spiral down the drain pretty quickly.

Quality pays, in my opinion, so I for my PC systems I only buy the more "premium" MB's that I've checked out the caps, or which have "overbuilt" regulators, like some fo the Gigabyte systems with dual 3 phase regulators for one CPU.

~Jon

[Kevin P]

See Badcaps for more information on bad capacitors on motherboards, and info on replacement. About a year ago I resurrected a 2000-vintage Gateway by replacing a bank of bad caps on the motherboard.

In Lex's case, it was probably not bad caps, if a cleaning and disinfection solved the problem. More likely, if it was a hardware issue, it was dust clogging up the heatsinks, causing something (CPU most likely) to overheat.

Or it was all the spyware on there that was cleaned off.