New PSU showing same problem as old

eldiablo696 · 4 Mar 2011 at 16:43

Hi All

I have recently upgraded my PSU from a fsp250w to a new seasonic 300w 80+.

I checked the power calculator for my specs and 300w was above the suggested wattage. I have added a newer graphics card and figured this into the power calculator. (too embarassed to say its only a fx5500, so dont tell anyone).

I did this because my 12v rail was showing 12.5v on the fsp.

My new PSU is also showing 12.5v on the 12v rail.

Is it possible that the device thats reading from my 12v rail is malfunctioning

or

That the 12.5v reading is how it has always been.

Or am I worrying about nothing.

Thanks

Fourstar · 4 Mar 2011 at 16:56

Most PSUs supply slightly over the rated figure. 12.5v is within the 5% tolerance given in the ATX specifications so there is nothing to worry about

You'll probably see it drop closer to 12V when stressing the CPU/graphics card.

Diggsy · 4 Mar 2011 at 16:57

What are you using to read the 12v?

If software, then it's probably picking it up wrong.

You might be better to grab a PSU tester, which is only a few £ and use that to test it, but chances are its a software / bios issue as it's highly unlikely the new PSU is at fault.

brendan · 4 Mar 2011 at 16:59

eldiablo696 said:
I did this because my 12v rail was showing 12.5v on the fsp.

My new PSU is also showing 12.5v on the 12v rail.

And where did you read that was not normal? To be ATX compliant the 12V rail has to be between +11.40 V to +12.60 V.

What you have to worry about is ripple or how stable that 12.5V is. And that's pretty hard to find out

I'd recommend reading :

http://www.anandtech.com/show/2259/4
http://en.wikipedia.org/wiki/ATX#Power_supply

eldiablo696 · 4 Mar 2011 at 18:39

Thanks

I got the readings from my bios - pchealth page and use pcwizard. I guess pcwiz reads from bios.

It does fluctuate from 12.47v to 12.6v, but averages at 12.54v. Is this what is known as ripple?

I will test the voltage. Do I just insert the prod into the molex. If yes, which pin. I think yellow is 12v?

Thanks for the confidence in knowing it is within ATX specs.

Been worried about this ever since I started looking in my bios.
I will look at the two articles.

Thanks again

eldiablo696 · 4 Mar 2011 at 19:08

I read the articles and feel a lot more confident that my psu is fine.

I also came across the following article, which I found quite easy to understand, given the subject matter.

http://www.dansdata.com/gz028.htm

Discusses the whole PFC or no PFC issue.

I got the impression that it will not save me money in electric bills, as advertised. But will help control ripple.

I will also know which component to look at if my tv, monitor or lights start to flicker.