A good question came up here yesterday: How do you know when your power supply is causing problems? There may be many power supply secrets, but that’s the one most important to know.

There are lots of symptoms of an under-rated power supply: frequent BSODs, spontaneous reboots for no reason, and the screen going black and the system crashing. A failing power supply can also cause other components in the system to fail much more frequently than they should. But generally you’ll see those other symptoms earlier.

Have you ever heard those horror stories about a lemon PC that’s had virtually every component inside it replaced at least once and it still doesn’t work right? Usually you can head off those kinds of problems. The trick is to replace the power supply after seeing two components fail.

In the previous story here, reader Glaurung asked if his IBM Aptiva’s 100-watt power supply might be causing him problems. He observed that two CD-ROM drives died in the system. I think it is.

IBM had a bad habit of skimping too much on the power supplies in its Aptiva and PS/1 lines. The business-class IBM PC line, in my experience, is good quality.

I don’t want to claim to know more about building a PC than IBM. But in that case I’d be replacing that power supply with something bigger. First check to make sure factory power supply doesn’t have any funky auxiliary connectors on it. A small few, especially those that mount their expansion slots on riser boards, do. Assuming yours doesn’t, a 400W unit from a reputable maker like Antec or Sparkle should only run $35 and prevent future peripheral death.

Usually, a low-power power supply becomes a problem when you start expanding. If you start with a system from a reputable maker (particularly a business-class system), the power supply ought to have enough juice to power everything they put in the box. You’re more likely to run into problems once you add a second hard drive and a CD burner. Some clone shops skimp on the power supply to save costs. The consumer machines you see in retail stores (like Compaq Presarios) typically have skimpier power supplies than business desktops (like Compaq Deskpros).

Whitebox systems built by your friendly neighborhood local clone shop vary. A lot of clone shops pride themselves on quality and build better computers than any of the big name brands. Other clone shops pride themselves on being cheap and cut every corner imaginable. The power supply is usually first.

While there are some really nasty motherboards out they aren’t as bad as they were in the past. Most causes of poor reliability in recent systems are due to cheap, commodity power supplies or cheap, commodity memory. PC Chips is notorious for making bottom-feeder motherboards. But given the choice between a computer with a PC Chips board and a quality power supply and quality memory or a computer with an Asus board with a no-name power supply and memory, I’d take my chances with the PC Chips.