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Testing PSU for stability?

Last response: in Components
September 15, 2010 2:39:41 PM

In order to know whether a PSU is the source of problem in a problematic system, one can try swapping the PSU. However, is there a way to test the PSU without swapping them? I only got one PSU.

More about : testing psu stability

a c 248 ) Power supply
September 15, 2010 3:01:49 PM

There are free software utilities which can monitor system voltages. You can use the utilities to see if the voltages are within acceptable ranges. I use a free utility that came with my motherboard.
September 15, 2010 3:23:59 PM

So if I got such program, what should I be looking for, stability-wise?
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a c 144 ) Power supply
September 15, 2010 3:35:20 PM

Main thing is the 12 volt bus. You want as little variation as possible over the load range. You also want all the voltages to stay in tolerance (plus/minus 5% except for the -12 volts which is 10%.

You cannot check noise and ripple without an oscilloscope.

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a b ) Power supply
September 15, 2010 4:11:02 PM

^ concur.

I use CPUID HWMonitor and utility that comes with MB, but other free ware is avail.
First you need to verify software works HDMonitor incorrectly reports my +12 V as a - 12 V. If the values are way off then it is a invalid value. I prefer to verify my voltage with a DVM, then I KNOW if I can trust the software. With a DVM block lead to black wire on a Molex conector. Red lead to the colored wires on the Molex (red = +5V and Orange or yellow = +12V.

With the software runing and the computer at idle Note the voltages (HDMonitor shows current, Nin and max values. Now run Prime 95 (or furmark in a window) and note the decrease in voltage, the less drop the better. +12 Must be above 11.4 (I chuck my PSU if it drops below 11.6V). The +5 V must not go below 4.75V - max for +5 V is +5.25 (These are standards, but also Min/max for TTL logic chips). The max for the +12 v is +12.6 - But as long as not above 12.8 should be fine.

The Big diff between a good PSU and a Great PSU is in the drop of the +5/+12V going from Idle to Full load. This is also where you may first see signs of a PSU going bad.

As jsc indicated, need a o'scope to check of spikes, ripple and noise. You can use a DVM to check for ripple, if under 20/40 KHZ (switching Freq and 60 Hz for AC Line rejection) by placing the the DVM in AC mode. should be in the millivolt range.

NOTE: Furmark will load the +12 V better than Prime 95 (Dependent on GPU)
Prime 95
September 18, 2010 3:50:00 PM

So...this looks sort of OK?

Voltage Values

CPU Core is 1.32 V

+3.3 V is 3.20 V

+5 V is 5.03 V

+12 V is 11.95 V

+5 V Standby is 4.87 V
a b ) Power supply
September 18, 2010 4:16:06 PM

Yes. Those are pretty fine.

Here are the ATX specs:
Supply [V] Tolerance Range (min. to max.) Ripple (p. to p. max.)
+5 VDC ±5% (±0.25 V) +4.75 V to +5.25 V 50 mV
−5 VDC ±10% (±0.50 V) –4.50 V to –5.50 V 50 mV
+12 VDC ±5% (±0.60 V) +11.40 V to +12.60 V 120 mV
−12 VDC ±10% (±1.2 V) –10.8 V to –13.2 V 120 mV
+3.3 VDC ±5% (±0.165 V) +3.135 V to +3.465 V 50 mV
+5 VSB ±5% (±0.25 V) +4.75 V to +5.25 V 50 mV
September 18, 2010 4:39:18 PM

Best answer selected by ionosphere.
a b ) Power supply
September 19, 2010 8:43:34 AM

This topic has been closed by Mousemonkey