Power supply or motherboard?

[Marty9231]

Hi

My pc won't properly boot up (i.e. all the fans turn, but there's no video input), so I have troubleshooted all parts. Eventually I put my PSU in another computer, to find that that one didn't boot at all. I concluded the PSU had to be broken.

As a last test I used a multimeter to manually test the voltages of the 24-pin connector and found that they were all next-to perfect.

Does that indicate that the PSU is healthy, and my motherboard must be dead?

Marty

 

[SNGX1275]

Does that indicate that the PSU is healthy, and my motherboard must be dead?

No. It just means that under essentially no load the PSU is delivering the proper voltages. The voltages supplied under load may dip well below what they are supposed to be.

 

[Marty9231]

Ok, then Is there a way for me to check if the PSU is faulty when under load? I ruled out the chance of my RAM and Graphics card being the issue, so is there a way to see if my motherboard is the specific issue?

Also, I put my PSU in another (older) computer, and that didn't even sound like it was booting (no fans, no LEDs). Does that mean the PSU is broken, or does it mean it's not compatible with an older computer with older parts.

 

[SNGX1275]

I don't have a real good answer to that, perhaps someone else will have one. I can only think of trying another PSU, borrow one from a friend or pick one up from someplace local that you can return....

 

[Marty9231]

Thanks for thinking anyway, If I were to connect a different PSU, I would connect one that doesn't support my graphics card. But it does support the one that I used to rule out mine from being broken. Would it matter to use that one, and see if it works with a different PSU?

 

[Lokalaskurar]

Ok, then Is there a way for me to check if the PSU is faulty when under load?

There is a method; connect several HDD's to as many 4-pin Molex-connectors as possible (or 7-pin SATA's - or even both!) and try to measure the voltage output on some unoccupied connectors. A bit more 'high-end' graphics cards usually draw a lot of power, so connecting those (if possible) is also a method.

Also, I put my PSU in another (older) computer, and that didn't even sound like it was booting (no fans, no LEDs). Does that mean the PSU is broken, or does it mean it's not compatible with an older computer with older parts.

Probably not. If the socket connector fit without any problems - then it's sure to be compatible. I use a ~20 year old PSU for testing hot-swap, it works just as well. The voltages have not changed inside the connector or anything.

It does sound like the PSU is faulty. But I would personally try to go with SNGX1275's suggestion before I jump to any conclusions.

 

[Marty9231]

connect several HDD's to as many 4-pin Molex-connectors as possible

My HDD´s don´t have this type of connection, they use SATA-300 cables. (I may be completely wrong, but I think I'm right) I have a High-end graphics card, so I should hook it up, and then what? Do I need to hook my HDD's and dvd-drive up, and then just fire up my pc and measure the voltage on an unoccupied connector? Does it matter what connector that is?

Also, Would it rule out my PSU if I did this:

-Replace the GPU in my pc with another, mid-end one
-Connect another working PSU (doesn't support the extra PCI-E connection my GPU uses, hence the other working gpu)
-Fire up my pc, and if I get video input, my own PSU is faulty.

 

[Marty9231]

Ok, so I used another PSU of which I know it works, and I got the same result: No video input.

One thing to notice is that that powersupply may have JUST had enough power to boot the system. Is that a problem big enough to say that the result isn't trustworthy?

Anyway, assuming that it isn't a big enough problem, does that rule out my PSU as being faulty and point to the only remaining part: the Motherboard?

Edit: would it be safe to test my (probably not broken) PSU in another computer? Because that's the last thing I can try here at home really. I was told that this brought a lot of risks with it, so I tried it on an ancient computer. I'd like to try it in a modern one, but I'm not sure it's entirely safe.

Edit 2: I have tested my PSU's voltage outputs while powering my machine with it, and the results remained perfect. Here's what I've done:

-Connected all devices to my motherboard (except my DVD-drive).
-Hooked my PSU up to a wall-socket
-Tested the pins of a sata-cable while everything was running

As I said, results were perfect, and everything was well withing the guidelines.
So, can I conclude that my PSU is good after this test?

 

[Lokalaskurar]

Ok, so I used another PSU of which I know it works, and I got the same result: No video input.

Then the diagnosis is instead that the motherboard is faulty, yes.

As I said, results were perfect, and everything was well withing the guidelines.
So, can I conclude that my PSU is good after this test?

If the voltage did not drop under load, then yes - the PSU sounds good. Only one thing left if you even want to further strenghten your diagnosis. To properly test this extra method, try to find a substitute PC that you can swap PSU's with. Put your PSU into the healthy PC, and see what happens. If it runs; your PSU is OK. If not, please let us know .

Wait, you said that all the fans turn, but still no video output? Because that sounds like a classical motherboard shortage. Have you been sneaking around inside the PC without using proper protection? No pun intended.

 

[Marty9231]

Put your PSU into the healthy PC, and see what happens.

I put it in an older PC already, which didn't start at all after the transfer. I did it again with a newer PC, and it started just as normal. Must have been something with the age of the older machine.

Have you been sneaking around inside the PC without using proper protection?

I have, sort of... I replaced my harddrive, but I discharged myself by touching the radiator. I'm starting to doubt if I did it right, because I didn't pay as much attention to it as I usually do.

Anyway, since the only remaining cause was my Motherboard, I ordered a new one, and it should be here tomorrow.

Thanks for the help!

 

[Lokalaskurar]

Don't mention it!