Bad Motherboard or PSU?

Hello and thank you for helping me.

Over the weekend I cleaned my computer by taking out the video card and the cpu and cleaning everything with dustoff. When I put it back together the computer would not turn on. There is no response from any drives or fans.

On the back of the power supply unit, near where the power cord plugs in, there is green light. While plugged in this green light is usually solid. Now, when the motherboard is connected to the PSU, the light will blink rapidly. When I disconnect the motherboard from the PSU the light on the back of the PSU will once again become solid.

I have tried disconnecting everything possible to eliminate any other faulty parts with no response from the computer. I have looked in the PSU and around the motherboard for burns or other indications of something faulty but haven't seen anything.

Do you have any recommendations for how to tell which part, if either, is in need of repair or replacement?

Thank you very much!

Some info:
I have a Sony Viao VGC-RB52 with an Intel Deskboard D945PPR
My power supply is stock with a max voltage of 300w (which has been fine, I haven't changed any parts lately)
6 answers Last reply
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  1. Re-check the power connections to your board - the 4/8-pin CPU power and the 20/24-pin main, to be sure they are firmly seated. Also, check the RAM and expansion cards to be sure they are firmly seated in their slots. If your GPU requires 1 or 2 external power cables, check to make sure the power cable(s) is/are properly connected to your GPU.
  2. I have checked everything for firm connections and bent pins but haven't found anything. I currently have all my RAM and cards removed from my computer to eliminate the chance that they are defective.
  3. You may want to look up the PSU to find out what the blinking light means.
  4. aford10 said:
    You may want to look up the PSU to find out what the blinking light means.

    Thank you for the advice! I had originally been doing this but had gotten sidetracked in thinking the powersupply or motherboard was fried.

    This is the solution I found, very strange:

    Starting with everything connected together and the power plugged in disconnect the motherboard, wait for the light to turn solid, reconnect the motherboard. Upon reconnecting the motherboard the light stayed solid and I was able to turn on my computer for the first time.

    Now I just have to hope I didn't mess up the CPU when I took it apart! to clean it! haha. I just learned that doing that can break a seal which helps keep the heat down, hopefully this didn't happen!
  5. Good deal...

    There is a coating of thermal paste between the HSF and the CPU. If you wiped it off, you'll want to apply new before powering on the computer.
  6. DDXV,

    Big thanks for mentioning that you got everything to work by reconnecting the MOBO with the power on.

    I had vacuumed out my old HP PC and blown out much crap with Dust-Off and I had the exact same problem--the PSU light would flash green and the PC wouldn't boot. After disconnecting everything and reconnecting boards and parts one at a time (unplugging the PC from the wall each time), it was obviously the main PSU-MOBO connection that caused the flashing. Reconnecting the MOBO with the PSU unplugged from the wall simply caused the flashing to reoccur when the AC was connected again. The only thing that cured the problem was reconnecting the MOBO -with- the PSU plugged in to the wall.

    It was something that I had not tried because it's a risky move (so sayeth my electrical engineering background). The HP site didn't suggest trying it either.

    Thanks again!!!
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