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notsure
07-10-2008, 04:37 PM
I'm having problems with my new power supply - or more likely when I installed the new PSU I stuffed something up. :redface:

The new psu is a Corsair vx550w - so 550w and more importantly 41A/492W on the 12V rail (full stats - http://www.corsair.com/products/vx.aspx


I recently had to upgrade hubby's motherboard & cpu - and at the time we couldn't afford a new graphics card (old one was AGP) - a couple of weeks ago we picked up a Point of View GeForce 7900 GT (our budget only stretched as far as the 8600 GT and since we didn't need dx10 I figured the 7900 was a better choice). Needless to say the old PSU was not going to be capable of running the card (aside from the fact that I was already running 1 hard drive externally due to a lack of power connectors). So finally today the new PSU was bought.

I hooked everything up (yes I do have experience and know what I'm doing - plus I also rechecked the manuals for the mb & psu just to be on the safe side) only to find that while I could get the system to boot and get into windows - after a few minutes it would just shut down - no blue screen no errors in the event logs - just no power).

At first I thought it may be an issue with trying to run too much on the psu - even though I did calc the requirements prior to purchasing. Needless to say I unplugged the graphics card first - with no luck - after some trial and error - I have the system running happily - however currently the dvd burner, floppy drive & video card aren't installed - I've also unplugged the front usb ports, power & hdd led's and the reset switch. Tomorrow I'll probably try plugging the dvd burner & floppy drive back in (hubby wants the floppy drive don't know why but hey) - and if that's successful I may even try the graphics card again.

In the meantime have I underestimated my power requirements - and if not does anyone have any suggestions on what else may be causing the problem.

System Specs (don't laugh it's a budget pc that will become a file server once new systems are purchased - already got a small mod planned for the one we're getting later this year :) )

MB: Asus P5GC-MX/1333
CPU: Intel Duel Core E2160
RAM: 1 x 2048 GB Corsair DDR2-SDRAM
Graphics: Point of View GeForce 7900 GT (if I can get it in & working).

2 SATA HDD & 1 IDE HDD (1 of the SATA's can be run externally in a powered bay if necessary)
Onboard Network & Sound,
some cheap keyboard (usb but connected to ps2 via adaptor) & mouse (ps2)

Any help/suggestions would be appreciated.

Thanks

notsure

Sepherus
07-11-2008, 03:03 PM
i often use this site for calculating power supply needs
http://extreme.outervision.com/psucalculatorlite.jsp

there is also a more advanced paid version (its $2 i think), but the basic one is good enough for me and it allows you to include cpu overclocking into the power supply needs.

also remember to take the result with a pinch of salt, i usually add 100W to the result that the calculator gives just to be sure that the power supply is gonna pump out enough juice

Luke122
07-11-2008, 03:08 PM
I did have a similar issue recently with another machine I built.. power needs calculated out at 400w, so we got a 550w psu. Turns out that it's not stable under load, so we are upgrading to a 750w.

As with any PSU calculators, definitely pad the results with at least 100w to be safe.

notsure
07-12-2008, 11:59 AM
I ran the calc before buying the psu - it worked out to less than 250 w (this really is a basic system) - but the video card manufacturer recommended a minimum of 550 w - I figured I'd go with that even though it's overkill, because I can then use the psu in 1 of the 2 new systems that I'm building later in the year - where the 550 w will be utilized more.

Anyways - turns out the problem isn't with the video card - I now have the system running stable with the video card installed & all drives powered & working (hdd/dvdrw/floppy) - only thing I've not yet plugged back in are the front panel usb ports, reset switch & hdd/power led's - so I'm assuming I plugged one of them in wrong when I first installed the power supply - no biggy - since I have 4 rear usb ports - plus a 4 port powered usb hub if needed...and I'm sure I'll survive without lights & a reset button.

Thanks for your help.