-5v rails on PSU

Ave

-5V rail on a PSU - what exactly is it, what does it supply, and is it ok if mines at -3.4?

Giblet

For analogue devices this would be used as ground, or to set a voltage to near zero.
If you put +5v on a wire, and -5 on the other end it would be zero.

Khannie

Ave wrote:

is it ok if mines at -3.4?

From what I understand, it doesn't matter a poo what the negative rail is at

The + rail is what people refer to when they're talking about rails.

Ave

Ok, it was actually at +3.55 on the -5v rail, so needless to say - I took out the PSU and put in my old one.

Time to RMA it.

Dempsey

What are you using to measure the voltages? The +5V, +12V, +3.3V, Vcore, Vdimm are the main rails to watch. My - rails are odd like yours but I dont care what they are. My PSU is fine.

Whats the PSU/Model/Power and what are you getting on the above rails while the PC is underload?

Giblet

It could be that the program you are using is reading the wrong voltages. Like the 3.4 could actually be the 3.3 line, but who knows.

Capt'n Midnight

Giblet wrote:

For analogue devices this would be used as ground, or to set a voltage to near zero.
If you put +5v on a wire, and -5 on the other end it would be zero.

There would be 10V across that wire.
Negative voltage is used on serial ports. Not sure what else it's used for

Dempsey

Capt'n Midnight wrote:

There would be 10V across that wire.
Negative voltage is used on serial ports. Not sure what else it's used for

The Voltages required for serial ports can be generated off the +5V rail. I did it for my project 2 years ago.

vishal

it is not a bad psu. i have a thermaltake butterfly 480watt and does the same thing. i asked in the hardocp forum and they said it has to be connected and being used to read the actual voltage. anyway that line isn't used nowadays and it dosn't matter. it is just a legacy line.

also if any of the other lines are stable but then suddenly changes dramatically the psu is still fine. the guy explained to me my it happened but i don't remember the answer. but if the psu was bad then you computer would crash and mine has never crashed since it was installed it 3 months ago. it is more stable then it ever was.

Ave

I used winbond hardware doctor and MBM5.

Every other rail was reported as within tolerance.

tribble

There is no point measuring the voltage with no load on the circut.
It just won't be accurate.

vishal

yeah that was the explanation. you have to load it first before you measure it.

Ave

tribble wrote:

There is no point measuring the voltage with no load on the circut.
It just won't be accurate.

It's always been reported within tolerance, even when doing the prime95 torture test + eve running in the background.