PC turns on for a second then off and again

Hi all.

I've strange problems with my PC for the last 3-4 days. When I try to turn it on, it actually turns on for 1/2 second (fans start spinning and I hear the HDD starting to spin - not at full speed just starting to spin) and then it turns off, on,off without I even touch it. The first thing I've though was it was shorting somewhere so I took it out of the case, placed it over motherboard's papercase and turned it on with screwdriver. It did the same thing. Its very weird because when I take off the AC/DC cable from the PSU and put it back in after 30-40 mins I am able to start the PC with one try sometimes. I personally think it's the PSU not able to spin the HDD at full speed at the beginning of the boot. My PC specs are:

Intel Core 2 Duo E6400
Asrock P5B-DE
2x 512 RAM, 1x 2 GB
HDD 160 GB 7200 RPM
ATI Radeon HD 4670 512 MB DDR3

The power supply is 350W. Sadly, the only extra PSU that I have around is 350W too and it does the absolutely same thing. Anyway, if I unplug the HDD or video or ram the PC starts everytime but ends up with error of the missing part. I explain it myself that the PSU wattage is too low to power up my build. Any advices? Should I change the PSU immediately?

 

Welcome to Major Geeks.

Based on your description, I agree the PSU is the most likely culprit. A video card such as yours normally requires between 14 and 18 amps of constant +12 volt output. If you have a cheap (generic) and/or older PSU, it's unlikely it's putting out enough amps to power the entire system.

I would get a quality, name-brand PSU in the 430-500 watt range. It will have more than enough power for your current video card (if you're planning on upgrading the video card in the next year or two, I'd jump to a name brand 500-550 watt PSU).

Corsair and Cooler Master make quality PSUs in the $35-$50 price range for a 430-500 watt model.

Hope this helps.

 

I will buy a new PSU in the next few days but I think it wont be a name-brand one cuz I've already spent my effords on new motherboard and CPU. Can you try to tell me why the system starts up successfully and I'm even able to play high-end games (the PC shuts down sometimes or shuts down immediately when I close the game and there is less load) ?

 

I would go to www.amd.com and check to be sure you have the latest drivers for your video card - if not, download and install them.

As for the power load issue, I based my response on your statement that the PC only starts up for half a second then shuts down. As for being able to restart it after 30-40 minutes, my guess is the existing PSU is overheating and has to cool down before it will (maybe) work again.

 

Not sure if its overheating problem since I've checked all the temps inside the PC and also, its very hard to overheat for 1/2 of the second. The PSU fan is blowing cold air. I will try with 500W PSU. Thanks for your effords.