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PC won't power on, PSU dying?


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#1 zico268

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Posted 17 March 2017 - 06:59 AM

Hi everyone!

 

I need help to troubleshoot and pinpoint what actually is preventing my PC from powering on. I suspect it's my PSU (Modecom Feel III-500 ATX) that is dying, because I read a lot about this model being crap. But I just want to be 100% sure it's the PSU before I buy a new one.

 

Forgive my simplistic language, but most the things I'm describing I'm not that knowledgeable about and I did them because I fallowed tutorials etc.

 

The issue is that when I push the case power button, nothing happens. Yet sometimes, after 20 seconds or 15 minutes it will just power on, boot up and everything looks ok. I tried shorting the power pins to power it on, in case it's the button that is faulty, but to no effect. 

I watched a tutorial on how to test your PSU with a multimeter and here is what I was able to measure. Firstly, when I shorted the green and black cables on the 24pin connector, the fans did start immediately, which I understand is good. Then the values are:

 

  1. Orange 3.17V
  2. Orange 3.17V
  3. Black
  4. Red 4.91V
  5. Black
  6. Red 4.91V
  7. Black
  8. Grey 4.91
  9. Purple 4.82V
  10. Yellow 11.62V
  11. Yellow 11.62V
  12. Orange 3.17V
  13. Brown + Orange (those two are in one pin) 3.17V
  14. Blue -10.73V
  15. Black
  16. Green
  17. Black
  18. Black
  19. Black
  20. Empty
  21. Red 4.91V
  22. Red 4.91V
  23. Red 4.91V
  24. Black
  • Also Green + Gray 4.49V

From the recommended values, I understand that all of those are low, but would it explain the issue I am having? What else should I check to be sure it's the PSU?

 

PC:

Mobo: ASUS P5K-E/wifi-ap

CPU: Intel Core2 Duo E8400

GPU: ASUS GeForce GTX 760

PSU: Modecom Feel III-500 ATX

 

I do understand that this PSU is borderline good enough to hold this GPU, but I bought that GPU about a year ago and everything was fine until now.



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#2 Chris Cosgrove

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Posted 17 March 2017 - 11:59 AM

Did you measure these voltages with the 24 pin connector removed from the mobo - off-load - or from the back of the connector with the computer running - on-load ?

 

If you measured the voltages with the connector disconnected from the mobo I would say there is concern for the state of your PSU. As you say, these voltages are low but within tolerance but if these are the off-load readings then you would expect them to drop further when connected to the mobo and the computer running which could explain your problems.

 

The simplest way to check a PSU is to replace it with another and see if the problem continues. If it does the PSU is almost certainly good, if the problem stops - ie the computer starts running normally - then it is probably a dying PSU. If you don't have a spare PSU lying around see if any of your friends have one.

 

Chris Cosgrove



#3 zico268

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Posted 17 March 2017 - 12:24 PM

I measured it off-load then. I didn't know how to do it, when it's connected. Like I said, I don't know much about it. But, yeah I will be leaning to buying a new PSU then. I wish I had another one so I could test it, that would be the easiest way, but I don't have other one unfortunately.

 

So  I guess this topic is done, I need a new PSU :/

thanks for your help :clapping:

 

EDIT! Oh, maybe to finish off, is it safe for other components to keep trying to power up on this PSU until my new one arrives? Or can it damage something?


Edited by zico268, 17 March 2017 - 01:29 PM.


#4 Chris Cosgrove

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Posted 17 March 2017 - 06:58 PM

No, it shouldn't do any harm. They are designed to fail safe.

 

To test this sort of connector when it is connected to the mobo you need a slimline probe. Years ago, when I was training as an electronics service tech, I made up a couple of probes for my meter with insulated crocodile clips on the end instead of the standard probes. These have the advantage that you can connect them continuously to anything, typically ground since this frees up one hand !  But it also allows you to put something like a piece cut out of a paper clip into the live lead to act as a fine tip probe. These leads are still in my toolbox.

 

Chris Cosgrove






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