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My computer won't turn on.

F

fatblueduck

Junior Member
Hi,

I built a new computer a few weeks ago (a pentium 4 640+, intel d945PVS motherboard, and an evga 7800 GT, in a TJ 06 case with 500 W power supply). Basically, m y computer doesn't turn on anymore.

I was in the middle of using it last night when most of my applications started to freeze. I started the operating system shutdown, but it stopped shutting down in the middle of shutting down and I had to turn of the power from the front of the case.

I turned on the computer after that, but only the fans turned on. I turned off the computer.

Now whenever I try to turn on the computer, the fans start to twitch, but then nothing happens and the light on the back of the power supply turns on for a second, but then goes out again.

I tried unplugging th power supply from the motherboard and plugging it back in again. I made sure that all of the plugs to and from the power supply were plugged in securely.

Also, I threw away the box to my antec power supply just last week, so if that's blown a fuse I'm screwed.

Chris
 
First of all, just a verification: you have your ATX12V cable connected, right? Two yellow wires, two black wires, the receptacle is at the upper-rear corner of the motherboard. And you have the video card's power cable hooked up too?

Also, which Antec 500W power supply do you have? The only one I can think of that's got a light on the back is the Phantom.
 
mechBgon,

Yes, I have both of the appropriate PSU connections plugged into my motherboard. The powersupply is an antec phantom 500.
 
The next thing I would do is to remove the motherboard from the case and lay it on cardboard. Unplug all drives from both power & data cables. Unplug non-essential wiring (USB, Firewire, etc). Try it like that, to see if it will stay running now.

If the problem was a short-circuit with the case itself, this will help reveal that. When PSUs only run for a split-second and then stop, short circuits are one thing that does come to mind.

See if that sheds any :light: on the situation or not?
 
mechBgon,

I don't know how to turn on the motherboard without using the button and connection from the case.

I unplugged everything from the motherboard except the powersupply and heatsink fan. The only thing that changed was that the fan on the heatsink stayed on for a few seconds longer.

I'm so disappointed with this antec psu.
 
i had a problem with my PC at a Lan this weekend. it shut down (just turned right off) during an intense frag-fest. when i tried to turn it on, the power was restored only long enough to twitch the fans. as it turns out, the lable on my rounded IDE cables may have been slightly conductive, as when i cut them off, all was well again.
 
to turn on the power supply without using th button...locate the 2 pins on the front panel header that the power switch connects to...momentarily short those pins with a screwdriver. This could be a power supply problem. The likelyhood of a case short circuit is greatly reduced by the fact that this problem occured while the PC was in a fully operational state. Not to say that it cant happen...its just less likely.
 
One quick question before I put a screwdriver to my motherboard. Would it be ok to try plugging in a PSU with a smaller mobo connection (fewer pins)?

If so, maybe that would be a gentler way of doing all of this.
 
Originally posted by: fatblueduck
One quick question before I put a screwdriver to my motherboard. Would it be ok to try plugging in a PSU with a smaller mobo connection (fewer pins)?

If so, maybe that would be a gentler way of doing all of this.
Click to expand...

Before you take your system apart: To test just your PSU separate of the system short pins 4 (green) and 6 (black) on your power supply connector with a piece of wire or a paper clip. You may need to scrap the coating off the outside of the ends of the paper clip as the coating of a lot of metal paper clips is non-conductive. If nothing happens when you plug it in and(and you're sure you scrapped enough coating off) then your PSU is toast. If the fan jumps or feebly tries to spin it's still your PSU. Sounds like a PSU issue or a grounding issue.
 
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