Troubleshooting a PSU

[illram]

Hi all

Today my PC decided to suddenly shut down. It was an unusually hot day and I have a tiny ITX PC stuffed with a bunch of crap so I am guessing it overheated. It did not POST on reboot after I let it cool down. I unplugged everything and attempted to boot it until it worked, component by component, and once the GPU (MSI 760 ITX) came out it POSTed. PSU also worked in an old PC I had lying around. Logical conclusion is GPU overheated, probably.

However... I am wondering if I could be misdiagnosing this as GPU problem. Looking through the grate on the PSU, I can see a little blue bubbly goo coming out of two white looking caps (shorter than the other caps) in the PSU. Not sure if that is significant. I have an old PSU lying around but it does not have the proper power connector for the GPU, so I cannot 100% be sure the GPU is dead. GPU fans spin but I assume that does not mean much.

So my question is: If the PSU is defective, could it still "work" but just no longer power its advertised wattage? E.g. can a 500w PSU have some sort of hardware failure such that it can still function at 250w or something? Or would a defective PSU just completely crap out and not work at all? My prior experience with busted PSU's is they just completely fail. PSU is 500w Silverstone Strider ST50.

Thanks!

 

[MrGreg62]

Absolutely if the psu has multiple 12 volt rails with one feeding the cpu and drives and the other feeding the gpu a power supply failure will cause the system to boot without the graphics card and not boot with it. It is a common problem that I have faced myself rma'd a 8800GTX and it still didn't work with the new card turns out it was the power supply.

 

[illram]

Thanks MrGreg62. That's something I am trying to avoid as well, although a free RMA is a cheaper troubleshooting venture that buying a whole new PSU, so I may just do that....sorry MSI.

I double checked and the ST50F has a single 12v rail pushing 408w. Can the hardware still degrade to the point where the single rail pushes way less power?

I looked at some PSU testers, would something like this show me that the PSU is underpowered? Looks like it only tests voltages, so not sure if that would properly diagnose the issue of whether the PSU is inadequately handling the wattage load.

 

[Tsumi]

Yes, if capacitors are dead, the PSU becomes unable to maintain the voltage when there's a sudden spike in demand for power. Removing the graphics card allowed it to survive the spike, while having the graphics card overwhelmed the weakened power supply.

No, basic PSU testers will not do anything. But anytime you have burst/leaking caps, you have a basically dead power supply.

 

[jojo69]

don't neglect our freebies thread, somebody probably recap that supply and run it

 

[illram]

Thanks all. One more question: do I run the risk of ruining any components by continuing to run the system (minus the GPU) via my onboard video with the damaged PSU?

 

[Tsumi]

If the PSU is unable to maintain ATX spec, yes. Which is highly possible, but impossible for normal people to determine.

 

[illram]

Good to know.

I only wish my PSU died bravely powering some awesome new game. Sadly my little killer ITX machine spent most of its time streaming Curious George on Netflix for my three year old daughter...