Stability of PSU

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <418bbc41$0$163$edfadb0f@dtext02.news.tele.dk>, David
Rasmussen says...
> I have a sneaking suspicion that my PSU may be unstable in that it
> delivers the wrong voltage on it's various lines.
>
> I know I can just look in the Health Monitor part of my BIOS, but I
> don't entirely trust those numbers, and also, I don't know what these
> numbers should be and how much they are allowed to fluctuate.
>
So how do you know they're wrong?

> Is there a program that can measure the stability and correctness of my
> PSU? I first thought SiSoft Sandra, but it doesn't seem to have a test
> for this.
>
Software will report what the motherboard says which is the same as
reported in the BIOS.

--
Conor

Opinions personal, facts suspect.

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Conor wrote:

> In article <418bbc41$0$163$edfadb0f@dtext02.news.tele.dk>, David
> Rasmussen says...
>
>>I have a sneaking suspicion that my PSU may be unstable in that it
>>delivers the wrong voltage on it's various lines.
>>
>>I know I can just look in the Health Monitor part of my BIOS, but I
>>don't entirely trust those numbers, and also, I don't know what these
>>numbers should be and how much they are allowed to fluctuate.
>>
>
> So how do you know they're wrong?
>

I don't. I suspect it. Because my system is unstable and I seem to have
tried anything else.

It's an expensive and supposedly excellent Antex 400W ATX PSU, so I
would expect it to work flawlessly unless it is broken.

>
>>Is there a program that can measure the stability and correctness of my
>>PSU? I first thought SiSoft Sandra, but it doesn't seem to have a test
>>for this.
>>
>
> Software will report what the motherboard says which is the same as
> reported in the BIOS.
>

Okay.

I installed SpeedFan which shows the reported voltages. But I don't
quite understand what it is telling me. It has three columns. The first
column has VCORE, +3.3V, +5V, +12V and -12V. All of these seem to be at
a reasonable level. The third column, though, _also_ has +3.3V, +5V,
+12V and -12V. And these readouts are not as good as the ones from the
first column. For instance, -12V is -8.43V(!) here, as opposed to
-12.53V in the first column.

I don't know what the difference between first and third column numbers is.

I someone would install SpeedFan (it is free and small:
http://www.almico.com/speedfan417.exe ), and run it and report their
third column numbers here, it would be really nice!

/David

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 05 Nov 2004 18:45:37 +0100, David Rasmussen
<david.rasmussen@gmx.net> wrote:

>I have a sneaking suspicion that my PSU may be unstable in that it
>delivers the wrong voltage on it's various lines.
>
>I know I can just look in the Health Monitor part of my BIOS, but I
>don't entirely trust those numbers, and also, I don't know what these
>numbers should be and how much they are allowed to fluctuate.
>
>Is there a program that can measure the stability and correctness of my
>PSU? I first thought SiSoft Sandra, but it doesn't seem to have a test
>for this.
>
>/David

There is no reliable software for aoltage readings, period.
Motherboard problems or simply the typical trace resistance
will effect voltage levels. The motherboard's report of
voltages was never meant to be the voltage level of the
power supply's output, only the voltage level ON the
motherboard, a different place in a different circuit.

Voltage readings must be taken with a
multimeter/voltmeter/etc at the connection to the load. For
example, at the back of the ATX connector for the
motherboard, the 4-pin molex for the drives.

Mentally reverse the following image for the ATX connector
pin-positions as you'd see then while connected to the
motherboard.
http://69.36.189.159/usr_1034/atx_on.gif

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 05 Nov 2004 18:45:37 +0100, David Rasmussen
<david.rasmussen@gmx.net> wrote:

>I have a sneaking suspicion that my PSU may be unstable in that it
>delivers the wrong voltage on it's various lines.
>
>I know I can just look in the Health Monitor part of my BIOS, but I
>don't entirely trust those numbers, and also, I don't know what these
>numbers should be and how much they are allowed to fluctuate.

Taking a hardware, multimeter reading at the connector, the
primary voltages of interest (and their acceptible
tolerances are):

3.3V, +- 5%
5.0V, +- 5%
12V, +- 10%

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 05 Nov 2004 18:45:37 +0100, David Rasmussen
<david.rasmussen@gmx.net> put finger to keyboard and composed:

>I have a sneaking suspicion that my PSU may be unstable in that it
>delivers the wrong voltage on it's various lines.
>
>I know I can just look in the Health Monitor part of my BIOS, but I
>don't entirely trust those numbers, and also, I don't know what these
>numbers should be and how much they are allowed to fluctuate.

The BIOS numbers *should* be the most accurate.

>Is there a program that can measure the stability and correctness of my
>PSU? I first thought SiSoft Sandra, but it doesn't seem to have a test
>for this.
>
>/David

The voltage sensing ICs on motherboards often use external scaling
resistors for the higher voltages, ie +/-12V and +/-5V. Health Monitor
is probably aware of these scale factors, but software apps such as
Sandra may not be.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.