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Is 500W enough?

jmart
Grafter
Posts: 34
Registered: 10-09-2007

Is 500W enough?

Just bought a http://www.foxconnchannel.com/product/Motherboards/detail_comparison.aspx?ID=en-us0000095 and teamed it up with an Arctic 500W PSU and it does nothing. When i switch it on, it stays on - the fans run and run, the lights stay on and you get that initial read noise from the HDDs. But there's nothing on the screen, and no beeps to indicate any errors. Not a dicky bird. The problem reminds me of when a friend built a PC but didn't buy a powerful enough PSU, but surely 500W is ample. I can find nothing on the above link about power requirements.
Please help.
Thanks in advance.
22 REPLIES
MrC
Grafter
Posts: 523
Thanks: 2
Registered: 17-07-2008

Re: Is 500W enough?

ASUS have a power supply calculator which might give you a bit of a guide.
http://support.asus.com/PowerSupplyCalculator/PSCalculator.aspx

Mike
jmart
Grafter
Posts: 34
Registered: 10-09-2007

Re: Is 500W enough?

According to that I only need 300W.
MrC
Grafter
Posts: 523
Thanks: 2
Registered: 17-07-2008

Re: Is 500W enough?

Oh dear Sad
All I can suggest are things you've probably already done, like religiously checking all cabling, reseating the memory, resetting the BIOS via the jumper, trying an alternative known working psu and, if you've got 2 dimms fitted, then try them separately. Also check that the case mounting pillars are all lining exactly up with the motherboard mounting holes and aren't touching the board anywhere else and causing a board to case short.
Is it a new cpu or one pulled from a previous board?
Mike
StickyMick
Grafter
Posts: 325
Registered: 29-11-2008

Re: Is 500W enough?

Don't just go by the wattage when purchasing a PSU. 500watts may sound enough but it all depends what's on the +12v rails. You can get a 600watt PSU, but if there's not enough on the +12v rail it may not even boot it, if it does it won't last very long
And those online PSU calculators are nothing short of misleading, as you've discovered.
For that motherboard I'm guessing you need at least 18amps on the +12v rails maybe more if you have a graphics card that needs input from the power supply. And that has to be a dedicated input as well, not slaved from a another connection.
jmart
Grafter
Posts: 34
Registered: 10-09-2007

Re: Is 500W enough?

Yeah, spent most of yesterday evening stooped over looking into the damned thing. checking jumpers, cables and other such stuff.
Anyway, the PSU is a known working one, this mobo was bought as an upgrade. One thing i have noticed, the board does bend slightly under the weight of the cpu heatsink & fan. But it's not hitting the case. Going to have to take apart my main PC to get at another PSU for testing. If that fails, it'll have to go back Angry
@stickymick:
the PSU does indeed have 18a on the +12v rails and the graphics will be the onboard one 'til i can get it booted
StickyMick
Grafter
Posts: 325
Registered: 29-11-2008

Re: Is 500W enough?

If you can source another PSU to try, then that would be a good starting point.
The symptoms you describe are an exact copy of what happened to me about 18 months down the line after I built my PC. I upgraded from an nVidia FX5500 graphics card to a 6600GT. Booted up one morning and it froze on the POST screen. subsequent reboots after that produced nothing but a black screen and drive lights permanently lit and fans spinning. I RMA'd the motherboard to ASUS and it came back with a clean bill of health. I didn't have a spare PSU so it had to go to the shop. Sure enough it was the PSU. I'm getting exactly the same thing now that I've upgraded to a 7600GT, but it will boot after a few tries.
Community Veteran
Posts: 1,571
Thanks: 3
Registered: 13-04-2007

Re: Is 500W enough?

A good trick with this type of error is to take the board out and sit it on newspaper with nothing else connected ie no hd's floppies cd's and try it then to see if it works. This rules out any shorts to the case and the hd's etc taking power. If it work then add hard drives/cd's one at a time. I fit all works out of the case then put it back and try but then you know there is no fault
jmart
Grafter
Posts: 34
Registered: 10-09-2007

Re: Is 500W enough?

I might give that a bash tonight. If the front panel leads don't stretch outside the case can I switch it on by shorting the two power switch pins with a screwdriver?
And can I also assume that using a grounded anti static mat would be safer than newspaper?
If it works outside the case fully fitted does that mean it's shorting on the case somewhere? Does anyone know where I can get a cardboard case?
Community Veteran
Posts: 14,017
Thanks: 539
Fixes: 9
Registered: 01-08-2007

Re: Is 500W enough?

Gotta say it does sound like a possibly defective PSU to be honest. I know you say it's known to be working... but that doesn't mean it hasn't gone wrong since it was last used as working! Something might of happened since then...
As others have suggested, first port of call is another PSU trial. If that also fails then it's probably the motheboard. I have heard of brand new boards being defective in the past. Its rare but it does happen. A friend of mine years ago had it happen... he wasn't happy and it took 2 of us to finally decide it was dead and tell him to take it back.
Personally though I would try at least 2 other PSU's in it myself. I inherited a 2.8GHz Celeron D machine from my local freecycle a while back. Nothing wrong with it other than the previous owner hadn't seated the CPU back into its slot properly. Anyway put that back, powered it up working fine! Took the PSU to bits and gave it a clean out... while holding it by the wires I accidentally dropped it. Didn't hit anything, it just hung from my hand dangling. No big deal right? Plugged back into computer, dead. I was trying everything for 2 hours until I finally tried another PSU and realised that in fact I had stretched a cable and snapped it internally! That is a very rare occurance for a cable to break inside its rubber shield.
Just goes to show that sometimes it really is worth trying that extra PSU as sometimes the working ones... don't work!
I need a new signature... i'm bored of the old one!
StickyMick
Grafter
Posts: 325
Registered: 29-11-2008

Re: Is 500W enough?

I'd certainly do a complete strip down and rebuild of the machine outside of the case. Lay the motherboard on a thick piece of card or a thin book on the side of the case to be sure all the leads will reach. Start off with just the motherboard and CPU with heatsink and fan attached, then try and start the machine, you should at least get BIOS beeps. And yes you can start the machine by shorting the two PWR/SW pins on the motherboard.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: 07-04-2007

Re: Is 500W enough?

Quote from: jmart
And can I also assume that using a grounded anti static mat would be safer than newspaper?

No, by the fact that it's grounded means that anti-static mats are conductive. From memory they are not directly grounded as there is a 1M ohm resistor in series.
StickyMick
Grafter
Posts: 325
Registered: 29-11-2008

Re: Is 500W enough?

The thing with PSUs is you could be running right on the ragged edge of it's capabilities. Upgrade something that needs just that little bit more power and that's all it takes to push it over the edge. It could be months before it goes, or it could go straight away.
I was a naughty boy and took the lid off my PSU last night. Sorry I did now Undecided There's 2 blown caps in there, so I'm on an emergency PSU hunt.
But be warned: IT'S NOT ADVISABLE TO TAKE A PSU APART They can store a lot of power and just one misplaced finger can be fatal.
jmart
Grafter
Posts: 34
Registered: 10-09-2007

Re: Is 500W enough?

Angry That was a total bust!  Angry
Same problem with both PSUs. Reckon it's RMA time.
Community Veteran
Posts: 14,017
Thanks: 539
Fixes: 9
Registered: 01-08-2007

Re: Is 500W enough?

Quote from: StickyMick
But be warned: IT'S NOT ADVISABLE TO TAKE A PSU APART They can store a lot of power and just one misplaced finger can be fatal.

I second that... although I'm one of the very worst abusers of it myself. Just last week I had my PSU in pieces greasing up the buzzing fan. What makes me worse for it is I had it turned on, LIVE, running the computer while it was in bits. I really should at least wear rubber gloves... I've had several shocks in the past though.. never nice. Last one was getting a computer back from my partners brother. They stuck the plug together with sticky tape. I pulled it out of the socket, sticky tape gave way, my finger slipped straight into the plug and hit the live terminal for a split second before a knee-jerk reaction flipped it back out!
Camera flash circuits... now they're fun if you want to learn to fly Tongue Last time I hit one of those I tele ported 2 feet backwards and landed in the wall  Cheesy Grin Wink
I need a new signature... i'm bored of the old one!