PC won't power on reliably

Old home built pc:

OS: Win XP
CPU: AMD Athlon 64 3000+
Motherboard: ABIT NF8-V
Memory: Kingston DDR PC3200 2g (2x1g)
PSU: Antec Truepower 330w ATX
GPU: Geforce FX 6800 GT
HD: Maxtor 250g
Drive: Lite-On DVD RW , 3.5" floppy
Sound: Soundblaster Audigy 2

My computer won't turn on everytime consistently. Started about a year ago. While it's on it runs flawlessly, and always has. After a shut down, most of the time I can power it on again. If I wait too long after a shutdown, it gets harder, taking more and more button presses to get it to start.

The red LED power light on my motherboard remains on, but the computer won't start, and the fans won't spin. I tried replacing the power button and also jumping the power wires, neither worked. Sometimes it works, most of the time it doesn't. I have to leave it on overnight if I want to use it the next day, hassle free.

Everything I've read so far suggests it's the PSU, I think it is most likely the PSU as well, but I would like some other opinions first.

If it does seem like a PSU problem, I would also accept suggestions for a replacement PSU from NewEgg.

3 answers Last reply Best Answer
More about power reliably
  1. Best answer
    More than likely, it is the PSU. At any rate, that's where I'd start first.

    The following is from one of my troubleshooting replies.

    Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button, then back to 5 volts when you release the case power switch. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    This is a pretty good choice:
  2. Very helpful, thank you!
  3. Best answer selected by bwitz.
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