New PSU - Now PC Wont Boot

Dear all,

I was recently having problems with my PC suddenly switching itself off after installing a new graphics card. I suspected the PSU wasn't up to the job so I have recently upgraded to a Coolermaster Silent Pro M850, however now that the new PSU is installed my PC won't boot. The green power LED on the motherboard is on and when I press the power switch the fans in the case and on the graphics card start spinning however theres no video on the monitor and oddly I don't get any POST beeps at all. I think that I can hear the hard drive spin up however the lights on the CD drives do not flash so I guess there is no power to them.

I reinstalled my old PSU (a Oryxx Tornado Model OX750-SD) and everything works fine again. I have also checked all of the connectors on the new PSU with a multimeter and all the voltages seem to be present and the correct value.

Any ideas you have will be gratefully received.

My other specs are as follows -

AMD Phenom II X4 965 Black Edition CPU
Asus M4N98TD EVO motherboard
8GB Corsair XMS3 memory
Microsoft Windows 7 Home Premium 64-bit
Arctic Cooling Freezer 7 Pro CPU cooler
Western Digital WD5001AALS 500GB Hard Drive


6 answers Last reply
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  1. Check the voltage indicator on the back of the power supply. In the US it should be at 115 and elsewhere 230 (although don't trust me if you don't live in the US and find out what your local power is at). You can probably just see what your existing power supply is set at and make sure the new one is the same.
  2. Hi,

    The PSU that I have doesn't have a voltage selector. The spec sticker on the side says that the input voltage is 110-240V so I guess it is autoselecting?


  3. I'd be interested in the answer to this as I have a similar problem. Do you have an 8pin or 4 pin cpu connector on your mainboard?
  4. I also have exactly the same problem having just upgraded to a OCZ ZX 850. I've tried removing the graphics card incase that was the problem. I've got a 4 pin cpu connector.
  5. usually the 4 pin is the cause for this issues. Also if it's a 20+4 main make sure it's firmly seated. I often have systems where these are not seated and people cant figure it out. Since you have no POST beeps, it's isolated to PSU-MOBO
  6. CHECK THE 4-8pin POWER JACK in the upper left corner. It is amazing how many people miss putting in this connector. It usually involves a cable that has to go directly over the top of the GPU card so they pull out the connector and never bother to put it back in.
    Check the manual to see what you forgot to plug in!
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