A builder's success

kw: little mysteries, computers

A few days ago, building a new computer, my son and I had reached an impasse. The motherboard would only turn on the power supply when it was outside the case. To this point, diagnosis had proceeded by shorting various pins together. When installed in the case and connected up, nothing would happen.

We removed everything from the case, and I got out a multimeter and began checking, from the wall plug inward. I verified that the power cord is OK, then found that, when isolated from everything but one system fan, the power supply was operating. However, this time I noted that the fan ran slowly (before, we'd just been excited that it turned at all), and that an LED on the fan (a decorative item) lit up dimly. Inspecting the power supply, I found a red slide switch with "230" clearly displayed. I slid it over to display "115", re-checked, and the fan ran at a more normal speed, plus the LED shone brightly. We'd been testing with the voltage set wrong!

Then we found that the power-on/power LED connection to the motherboard was back-wired. Once we turned the plug around, the motherboard fired up and soon it beeped. It was booting up! Back in the case, though, it was inert.

We bought nylon screws and nuts and made insulating washers out of acrylic material (a viewgraph blank). Finally, with everything connected, including a monitor, we got the computer to boot up and request the system disk. Since then, things have gone smoothly, with only one glitch: Once Windows Vista was installed, and the video drivers loaded, Vista has a program for tuning the system and determining its "Experience Factor". The program stress tests the CPU, memory and video card. The power supply cut out in the middle of this test! We took a break at the local Five Guys and had a burger. That was my Father's Day dinner.

When we returned, we hit the start button, hopefully, and the machine booted. The power supply, as I hoped, has a thermal breaker, and had reset itself. We did the stress test while the power supply was still cold, and everything worked. This PS is 450 watts, and I did find literature on the Web that recommends using a 500W PS with this motherboard/CPU/video combination. If the power supply gets in the habit of cutting out, we'll replace the power supply with one that supplies 580 watts, the largest one compatible with the case.

Learnings:

• Insulate the motherboard from the case.
• Make sure plugs are the right way 'round. Most of the plugs only go one way, but the smaller ones can go either way, and polarization still matters. The documentation is not as clear as I'd like.
  
• Verify the voltage setting on the power supply.
• Make sure the motherboard-plus-CPU boots up before putting it in the case.
• It is possible to straighten bent pins, but if the CPU won't simply fall into its socket, something is wrong, so check the socket (count pins to blanks if needed), and make sure all pins are straight from the get-go.
• These components are amazingly robust. We made several serious mistakes, but wound up with a running computer.
• Finally, there are no economies to building a computer. Dell, Gateway and others pay a lot less for components, so much less that they can build the computer to order and still charge less than you'd pay for components. But when you are done it is your machine!