PC won't intermittenly turn on!!

Asus P5p43td pro
September 10, 2009 at 13:25:13
Specs: Windows Vista
I have built a pc around 3 weeks ago. When i first got the pc together it would turn on. I bought a new PSU, and it turnd on ( for a few days). A few days later, it wouldnt turn on atall !! Bench tested the MB and PSU only. Green light was showing on the MB but still no boot up. As if there was now power cord plugged in. I sent the MB back to the shop, they bench tested it, fired up first time. They sent it back, ssaying there was no problem.

I then got it back a yesterday,and it worked for 2 hours. I then turnd it off and tested it again. It wouldn't boot. I took the MB battery out, and placed it back in, and it booted up....

Today its not working atall !!!

I'm all out of ideas, surely if it was a bad MB it wouldnt have worked allt he other times (and when i sent it back to the shop)?

Any help will be appreciated!


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September 10, 2009 at 13:49:39
There may a poor connection inside your case somewhere.

Unplug the case/power supply.
Power off your monitor.
Open up the case by removing the left panel as seen when you're looking at the front of the case.
Check all the connections of the wiring to make sure they are all the way onto their pins and into their sockets, especially the main connector from the power supply. The wires close to the mboard going into the main power connector/socket should be more or less perpendicular to the mboard surface rather than at an angle. Most mboards require an additional connector from the PS be connected to a socket for power on the mboard, other than the main socket. Make sure all cards in slots are all the way down in their slots.

A common thing that can happen with ram, even ram that worked fine previously, is the ram has, or has developed, a poor connection in it's slot(s).
This usually happens a long time after the ram was installed, but it can happen with new ram, or after moving the computer case from one place to another, and I've had even new modules that needed to have their contacts cleaned.

See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:

Failing power supplies are common and can cause your symptoms.
Check your PS.
They often partially work, fans and hard drives may spin, leds may come on, yet you may get no video and the mboard will not boot all the way.
See response 4 in this:

If it is failing, you can usually replace it with any decent standard sized standard ATX PS with the same capacity or greater.

Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.

Don't buy an el-cheapo PS.
See response 3 in this:

Your power supply must have at least the minimum capacity required to support a system with the graphics card you are using installed, or the max graphics card you might install in the future.
(Onboard video - video built into the mboard - IS NOT A CARD!)
You can go to the video card maker's web site and look up the specs for the model - often under system requirements - the minimum PS wattage, and, more important, the minimum amperage the PS must supply at 12v is stated. If you don't find that, any card with the same video chipset including any letters after the model number has very similar minimum PS requirements.
Some power supplies have more than one +12v amperage rating - in that case you add the rated max amperages to determine the total +12v amperage rating.

If the PS doesn't have enough capacity, a video card often works for awhile anyway, but the PS is overloaded 100% of the time and is eventually damaged and fails.

Open up your case and examine the mboard to see if you have bad capacitors, and/or other findable signs of mboard damage .

This was the original bad capacitor problem - has some example pictures.
History of why the exploding capacitors and which mboard makers were affected:

What to look for, mboard symptoms, example pictures:
Home page that site
- what the problem is caused by
- he says there are STILL bad capacitors on more recent mboards.

Pictures of blown capacitors, other components - power supplies, Athlon cpu's, etc.:

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September 10, 2009 at 13:55:04
Why didn't you post any info about your power supply? Is it a name brand unit, at least 400W, with 30A or more on a single +12v rail? Did you spend at least $50 for it?

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September 10, 2009 at 14:02:00
Hi the PSU is the OCZ 700 WATT Sciilent modle. Cost me £70.00. i have tacken the MB out. no ram, no card just the MB, PSU and CPU... no power up :S

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September 10, 2009 at 14:31:44
Pull the RAM and see if you get error beeps. If so, that would indicate a RAM problem.

No beeps with the RAM out? I would suspect the power supply.

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September 10, 2009 at 14:46:05

i have 3 different psu's, 2 are brand new! i cant be that. The green light is on the MB. I sent the MB back to the shop yesterday, and it booted up for them 1st time. When i received it back, it booted up for me. until today... it wont turn on ... not the PSU :( any other ideas ?

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September 10, 2009 at 15:21:17
Remove the motherboard and check for a standoff in the wrong place. Standoffs should be placed under each screw hole in the board and no where else.

Do you have the CPU auxillary power connector fitted to the board as well as the 24 pin power connector?

If you have a high performance video card you may need an auxiliary power connector to that too.

Re-seat all cards, cables and RAM.

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