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PSU Starts Then Turns Off?

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  • Power Supplies
  • Components
Last response: in Components
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November 21, 2010 12:49:36 AM

Hello,
Another PSU question, yay. I recently upgraded to a Corsair 700w Gaming PSU. Well, I plug in all the components to my PSU and I get a 1 second run life and power down.

I then I have to unplug the PSU and back in to get it to run again.

The tricky part is I know I didn't fry the mobo because when I connect my old PSU everything starts up fine.

I have tried it when just the MOBO and it starts the fans for only a second then powers down.

Solutions? Is the new PSU just bad?Is it detecting a short and my old PSU didn't? Am I just that fail that I am missing something?

Help please :) 

More about : psu starts turns

November 21, 2010 1:24:10 AM

hunter315 said:
Take a case fan and test the PSU using this method, if it cant keep the case fan going then RMA it.
http://www.youtube.com/watch?v=5FWXgQSokF4


Okay I have tried this test with the case fan and the fan ran perfectly fine. Now what? Is it a null point and the PSU won'y fire up my MoBo and I will never be able to use my GTX 460 card because my PSU is lame?

Oh this Saturday is terrible. Lol.
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a c 144 ) Power supply
November 21, 2010 1:43:46 AM

Corsairs are much a better than average PSU. And 700 watts is more than enough to power your system. Even a good 550 watt PSU would be enough.

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.

I have tested the following beeps patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:
http://www.cwc-group.com/casp.html

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

Motherboard LED's mean very little. When on, all they are telling you is that the computer os plugged into a live power socket and the PSU is switched.

Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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a b ) Power supply
November 21, 2010 2:11:56 AM

Ok, this will probably not help but what the hey.... I just got a Corsair HX850w for an upcoming build and I did not intend on using it right away so I needed to test it before the 30-return period was up.

I unhooked my old PSU and removed it from the case, for simplicity and ease I left the Corsair on the table and plugged everything in, I could not get it to start my PC like that no matter what I had tried(everyting I could think of / quadruple check everything) and had the same issue as you, fans spun for a second at most then... dead nothing.......But when I place the PSU in the case and installed it correctly everything worked perfectly.
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November 21, 2010 11:17:09 AM

Just attempted to test the PSU on a work computer and it failed to start this mobo as well. going back to Best Buy today to exchange PSUs. Will update following.
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