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PC Power Supply

N/A

PC Power Supply

I noticed yesterday whilst running some pc health status software, that the voltages on my power supply's -12V & -5V rails were only reporting -1.56V & -2.35V respectivly.

I checked in the BIOS and the values are reported as the same.

I haven't really noticed any problems with my PC, but does this mean the power supply is failing and should I replace it ASAP?
11 REPLIES
Community Veteran
Posts: 38,307
Thanks: 972
Fixes: 57
Registered: 15-06-2007

PC Power Supply

Probably just misreporting
p_w_d_stone
Grafter
Posts: 315
Registered: 05-04-2007

PC Power Supply

I'd be extremely surprised if your PC was running with those values. Hard disc drives and CD/DVD drives simply wouldn't work as there wouldn't be enough power to run their motors. The rule of thumbs is that a 12v rail that drops below 10.5v means a dead PSU and the computer will not boot. Anything below 11v is a cause for concern, and you should replace the PSU.

If you're a confident and competant tech, you could test this yourself with a multi-meter. There's a useful article here on this.

Risk to hardware: The article is written by an American author. The following quote should be disregarded-

Quote
Next, check the voltage selector on the back of the PC near the fan to make sure that it is in the 115-volt position.


European electricity distribution uses 230 volts- the setting on your PSU should therefore be 230 or 240 volts.

Health warning: As always when using electricity there a risk potentially dangerous shocks. Use caution when testing power supplies and, if in doubt, get someone who knows what they are doing to do this.
Community Veteran
Posts: 14,469
Registered: 30-07-2007

PC Power Supply

@Peter,

You appear to be confused between the +12v & +5v rails which are used extensively throughout the system and the -12v and -5v mentioned here which have very little to no use on today's mobos, hence why they only tend to have 1 or 2 Amps available and why the system appears to still operate fully.

@hughes2002,

Its possible that your system does not require those voltage rails so them being so low will have no impact. However they should not be that low and could indicate a fault within the PSU, which may mean its on its way out. So even though things may be working now I would recommend you source a new PSU before it fails completely.
N/A

PC Power Supply

Thanks for the advice.

I was thinking it would be sensible to replace it just incase.

Any advice on what power supply to go for. There seems to be a range of prices for similar specs.

Are the cheap ones to be avoided.

For example:

http://www.7dayshop.com/catalog/product_info.php?cPath=777_5&products_id=102234
Community Veteran
Posts: 38,307
Thanks: 972
Fixes: 57
Registered: 15-06-2007

PC Power Supply

Basically you get what you pay for.
It is definitely not worth going too cheap.
Have a look at this thread http://forums.extremeoverclocking.com/showthread.php?t=136602
I have found FSP to be fairly good and not too expensive
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: 18-07-2007

PC Power Supply

I've been doing some looking in to this as a new PSU is on the cards for me this month (roll on monday - pay day, that is) and was going to get the corsair 520 - following holtlane's link above has showed me that this is indeed the right choice.

I'll be getting it from here - it's for an athlon 64 3400 w/2 sata and 1 ide drives and a geforce 7800GS (AGP) so if you have a similar spec, or at least only run 1 graphics card, this would be the way forward.

Oh - and it comes with a 5 year warranty. :shock:
Moon on a stick, anyone?

Hope this helps,
jrgrahamcov
Grafter
Posts: 160
Registered: 01-08-2007

PC Power Supply

Thats a very good website to buy things from. I lost the driver disk to an OEM sound card (drivers not available on the internet) and gave them a call. They posted me another CD which arrived 2 days later.
p_w_d_stone
Grafter
Posts: 315
Registered: 05-04-2007

PC Power Supply

I've also had excellent experiences purchasing from Overclockers.
Community Veteran
Posts: 38,307
Thanks: 972
Fixes: 57
Registered: 15-06-2007

PC Power Supply

jrgrahamcov
Grafter
Posts: 160
Registered: 01-08-2007

PC Power Supply

I have ordered a wide variety of parts from them (graphics cards, motherboards , CPU's , RAM, PSU's , sound cards, headsets etc,etc) and in each case delivery was quick and everything was fine. If they are a poor company I thought I would have been stung by now.
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: 18-07-2007

PC Power Supply

Likewise - I've ordered a number of different items from overclockers and never had any issues. I appreciate that all sides of an argument need be shown, but do not know anyone personally that has had a problem with this site and would recommend it heartily to anyone.