Did I fry my motherboard or my power supply?

I just installed a second video card (GeForce 7900 series) alongside my older GeForce 6700 Series. After the computer was powered on for about a day, I came back to find the unit dead, with the power button not responding at all. After changing the plug from a power strip to a different wall socket, it seemed to partially power on, with these results:

• Two of the three case fans were operational
• The motherboard's green LED was on
• The GeForce 6700's fan was operational
• The DVD drive made standard bootup sounds

However, the CPU fan was not on, one case fan was not on, and the GeForce 7900's fans were not operating. Additionally, after pressing the power button to turn the computer on, it could not be turned off by anything except flicking the PSU's power switch.

Here are the machine specs:

• Rosewill Capstone-650 (650 watt power supply)
• Asus P8B75-V motherboard
• Two graphics cards (as described)

I removed both video cards, but nothing changed. I have a strong feeling I fried some combination of the motherboard, the PSU, and possibly the graphics cards - possibly because my PSU wasn't powerful enough to handle the load. Can anyone shed any insight on this?

Solution 1:

What brand is the power supply? As with most equipment, budget brands tend to over-rate capacity by measuring only perfect conditions. If something in it was blown, you may be able to detect some smokey smells from it faintly (worth checking). It may also be worth using a digital multimeter to confirm your voltages are in spec, usually +/- 5% of rated voltage. Connect the black probe of your meter to a black wire on a molex connector and the red probe to the red wire, and then the yellow wire. You should see 4.9-5.1 volts, and 11.8 to 12.2 volts (roughly). If voltage is far off from there, it's probably a bad supply or another component causing excessive draw.