Odd PC Voltages

[John Keiser]

The PSU on my wife's old Sony PCV RX766 blew in the recent power outage here
on Oahu. A Sony replacement PSU is too expensive but I made a generic fit
OK. PC seems stable and works fine.
In testing with the latest Everest, I get some odd results:

CPU temp is 53 degrees C. Seems high. I added an extra fan. Still high.
MB is 34 degrees C.
HD is 35 degrees C.

More perplexing are the negative voltages:

CPU Core 1.48
Aux 3.09
+3.3 3.33
+5 5.08
-12 -9.32
-5 -7.71
+5 S/B 4.44


I don't see a + 12 or +5 displayed. The -12 and -5 seem way odd since
eveything works well.

Shouild I be concerned?

Thank you for any comments

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[Jeroni Paul]

More perplexing are the negative voltages:

CPU Core    1.48
Aux             3.09
+3.3            3.33
+5               5.08
-12             -9.32
-5               -7.71
+5 S/B         4.44

I don't see a + 12 or +5 displayed.  The -12 and -5 seem way odd since
eveything works well.

Shouild I be concerned?

I would not worry about that. However you could measure them with a
reliable voltmeter to be sure. -12V are used for the serial port, if
you have something connected there like a serial mouse that could
explain the voltage drop. If it works, leave it as is. I think there
is nothing nowadays using the -5V rail so that could explain it is
slightly higher.

 

[Jamie]

John Keiser wrote:

The PSU on my wife's old Sony PCV RX766 blew in the recent power outage here
on Oahu. A Sony replacement PSU is too expensive but I made a generic fit
OK. PC seems stable and works fine.
In testing with the latest Everest, I get some odd results:

CPU temp is 53 degrees C. Seems high. I added an extra fan. Still high.
MB is 34 degrees C.
HD is 35 degrees C.

More perplexing are the negative voltages:

CPU Core 1.48
Aux 3.09
+3.3 3.33
+5 5.08
-12 -9.32
-5 -7.71
+5 S/B 4.44


I don't see a + 12 or +5 displayed. The -12 and -5 seem way odd since
eveything works well.

Shouild I be concerned?

Thank you for any comments

either you using your DMM incorrectly with the common probe placement or

you have an issue with the - output side the supply..

Looking at the -12 line and seeing it's only -9.32 volts, this maybe
due to excessive load, the -5 line being over voltage could be a
by product of the PSU trying to correct the -12 and the -5 is regulated
on it's own.
I would worried about the -5 being high.., I think you should
correct that.


http://webpages.charter.net/jamie_5"

 

[Eeyore]

John Keiser wrote:

The PSU on my wife's old Sony PCV RX766 blew in the recent power outage here
on Oahu. A Sony replacement PSU is too expensive but I made a generic fit
OK. PC seems stable and works fine.
In testing with the latest Everest, I get some odd results:

CPU temp is 53 degrees C. Seems high. I added an extra fan. Still high.

Hardly high for Hawaii ! Silicon functions up to vastly higher temps than that.
Why do you think it's high ?

MB is 34 degrees C.
HD is 35 degrees C.

More perplexing are the negative voltages:

CPU Core 1.48
Aux 3.09
+3.3 3.33
+5 5.08
-12 -9.32
-5 -7.71
+5 S/B 4.44

I don't see a + 12 or +5 displayed.

Yes, the +5 is +5.08.

You could buy a cheap DMM and measure the +12 on an unused drive connector if it
worries you !

The -12 and -5 seem way odd since eveything works well.

Negative voltages are hardly ever used these days so it's probably 'out of
regulation' due to no load.

Graham

 

[Eeyore]

Jeroni Paul wrote:

-12V are used for the serial port

They usually have their own charge pumps these days. Remember the spec goes
back to 1982 or so.

Graham

 

[Eeyore]

Jamie wrote:

I would worried about the -5 being high.., I think you should
correct that.

TWAT as usual. NOTHING uses -5V these days AFAIK. I think it was needed for very
early DRAM, that's all.

Graham

 

[Jamie]

Eeyore wrote:

Jamie wrote:


I would worried about the -5 being high.., I think you should
correct that.


TWAT as usual. NOTHING uses -5V these days AFAIK. I think it was needed for very
early DRAM, that's all.

Graham

And you would gamble on that?

For your info ass, I have recent PC and the -5 is very well used in it.

http://webpages.charter.net/jamie_5"

 

[Franc Zabkar]

On Sun, 28 Dec 2008 20:56:27 -1000, "John Keiser"
<john.keiser2@hawaiiantel.net> put finger to keyboard and composed:

The PSU on my wife's old Sony PCV RX766 blew in the recent power outage here
on Oahu. A Sony replacement PSU is too expensive but I made a generic fit
OK. PC seems stable and works fine.
In testing with the latest Everest, I get some odd results:

CPU temp is 53 degrees C. Seems high. I added an extra fan. Still high.
MB is 34 degrees C.
HD is 35 degrees C.

More perplexing are the negative voltages:

CPU Core 1.48
Aux 3.09
+3.3 3.33
+5 5.08
-12 -9.32
-5 -7.71
+5 S/B 4.44


I don't see a + 12 or +5 displayed. The -12 and -5 seem way odd since
eveything works well.

Shouild I be concerned?

Thank you for any comments

The first thing you should do is to compare your readings with what
BIOS tells you.

The motherboard's hardware monitor chip probably has a multi-input A/D
converter with an internal 4.096V precision reference. This means that
any voltage outside the range of 0V to 4.096V has to be scaled down
via an external potential divider. The Vcore and 3.3V inputs could be
measured directly, but the others cannot. Negative voltages would
require a DC bias. The potential divider ratios would be known to the
BIOS but not to Everest. Hence the BIOS readings can probably be
trusted, but not those of any software tool. Remember also that the
hardware monitor is seeing these voltages as they appear on the
motherboard, not at the PSU. Hence you need to be aware of voltage
drops in the cables and in the motherboard traces.

I prefer to use Motherboard Monitor, but unfortunately support for it
ceased many years ago. MBM 5 allows you to specify your own voltage
divider ratios and many other parameters.

- Franc Zabkar
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