Question How can you test to see if a PSU has definitely gone bad ?

[80251]

I have a 13 year old Rosewill Capstone 750 Watt 80 Plus Gold PSU that turned out to be the whole reason I had unstable overclocks w/my 9700k (@ 5.2Ghz.). The thing is, according to HWiNFO64 and my DMM, all voltages are always within the 5% margins specified by the latest ATX standard and usually higher than the referent voltage. On swapping PSUs though all the problems w/my present overclock disappeared. I'm guessing the ripple voltage must have been really bad under load, but I guess there's no way to test for this without an oscilloscope.

 

[steveb1976]

there are devices out to test "psu, and its cables" check amazon and ebay... they are cheap to buy and hand to have.

 

[Syntaximus]

There's always the paperclip method, but using a multi-meter is better.
Lots of guides out there (all similar for the basics), here is one is from Microcenter.

 

[steveb1976]

https://www.passmark.com/products/i...supply voltages are,and current for each rail.

 

[80251]

https://www.passmark.com/products/inline-psu-tester/index.php#:~:text=Download-,Inline PSU Tester,your desktop PC power supply.&text=Check power supply voltages are,and current for each rail.

For $434, that certainly isn't a cheap piece of equipment but it sounds like what I was looking for. Thanks.

 

[steveb1976]

i was showing you the device as an example of what to look for... you can get them in the U.S.A and U.K for a fraction of that price.

 

[geofelt]

The only way I know of is to replace with a quality replacement of sufficient power.
psu operations are complex and simple voltages do not tell the whole story.

 

[Grobe]

There's always the paperclip method, but using a multi-meter is better.

The paperclip method is only useful to test if the PSU is completely dead.

However, a common failure of many CPU's is that they tend to degrade over time in such a way that they cut power at much less wattage than rated for.

Another common issue about paperclip + multimeter method is that when no load, even a bad PSU may seemingly be healthy - because you may read a steady +12V voltage.

 

[Eximo]

PSU load testers are quite specific. The PSU testers on the market that are affordable check the voltages, hold up times, and ripple for the most part They still can't tell you if the PSU can handle a load.

13 years is well beyond the service life of the main capacitors. It should be replaced as a precaution regardless.

 

[80251]

@Eximo
I did check the caps on removing the PSU, the electrolytics all looked good (no leakage or bulging).

On further testing it seems like the old Rosewill Capstone 750Watt might not have been the issue w/my CPU core overclocks, but it had other weird issues. Occasionally anything connected to the SATA power connectors would disappear (HDDs, ODDs) and I'd have to power down the system and plug/unplug the SATA power connectors to get them working again.

 

[Grobe]

PSU load testers are quite specific.

Yes totally agree, but I assume most users asking about bad PSU doesn't have quick and easy access to such a tester - if not specifically telling so in the first post.

 

[geofelt]

The ONLY way to determine if a PSU is bad is to replace it with a new or known good PSU.
If such is not available on loan, buy are placement from a shop with a good return policy.
Expect to pay a 15% restocking charge if you need to return it.

As an anecdote, the cpu on a pc failed. I replaced with a new cpu.
The old CPU was still under warranty and I returned it to Intel where it was confirmed defective and was issuesd a refund.
The new CPU worked fine but I got occasional blue screens that I could not figure out.
Bios updated, driver updates, new windows, all failed after a few hours or days of use.
Tested on a new identical motherboard.
No indicators of a faulty psu.
Drove me crazy.
I replaced with a back up psu and all was well.
In retrospect, the bad psu may have caused the original processor to fail.

Bottom line, if you suspect a psu problem, replace it with a good one regardless.
A psu with a 7 to 10 year warranty is likely to be of good quality.

 

[nostall]

A few years ago had a very similar problem with an original Corsair AX850; It started acting up when it was around 10 yrs. old (purchased 6/2010) and it took a long time to actually figure out that it was the problem. All rails checked multiple times with a multi-meter and always showed proper voltage. Only solution was borrowing a friends PSU, and using it the problems disappeared. Old AX850 was quickly replaced with an RM850i.

 

[Grobe]

A faulty PSU can compare to an old car where most of the metal body are rusted beyond any repair but the outer paint layer still spotless. You can probably drive the car if just low speed within the farm fence.
But taking that car on the public road with only the paint holding it together, it will most probably fail in the very next turn, or when it pick speed.

 

[mono09]

To definitively test if a Power Supply Unit (PSU) has gone bad, you can follow a few steps. First, perform a visual inspection of the PSU to check for any obvious signs of damage such as burn marks, a burnt smell, or frayed wires. If any of these signs are present, it's a strong indicator that the PSU might be faulty. The next step would be to use a PSU tester, which is an effective tool designed to check if the PSU is delivering the correct voltages. You can connect the PSU to the tester, and it will display if all the necessary rails are functioning properly. If the tester shows any of the rails as "out of range" or "fail," this suggests the PSU is defective.

Alternatively, you can use a multimeter to measure the voltages directly on the 24-pin motherboard connector, checking for the correct voltages on the 3.3V, 5V, and 12V rails. If any of these are off, then the PSU is likely bad. Another common method is the paperclip test, where you short the green wire (PS_ON) 🤢 and any black wire (COM) on the 24-pin connector to see if the PSU fan spins when powered on. However, this test is basic and doesn't provide comprehensive results.

Lastly, a practical test would be swapping the suspected faulty PSU with a known working one; if the system powers up fine with the new PSU, then the original PSU is most likely the issue. Keep an eye on system behavior, such as random shutdowns, reboots, or failure to power on, which are all potential signs of PSU failure. Always exercise caution when performing these tests to avoid causing further damage or harm.