Unable to Turn On Self-Built PC

  skaria 02:07 03 Aug 2007

Hello All,

I built my own pc about 2 years ago, and am now having trouble turning it on.

The PC consists of an AMD ATHLON 64 processor, and Asus A8n-SLi Premium mothrboard, and bvidia 660gt graphics card, and geil ram.

Before the PC "broke" I was getting blue screens very often - which occured at various times after I had turned the PC off.

However, on opening the case I found out that the fan controller knob that controlled the CPU fan was faulty - that is to say, that if the fan controller was not set to the maximum level, it would not be on! Note, before I had opened the case, I had turned the fan controller on to the full setting a few times - so the CPU fan was at its maximum - and the blue screens still occured. Im not sure, but I do not think the fan could have been off for the whole period of time that the blue screens ocurred, but it is fair to say that it is possible that the cpu fan may have been off for some time (days or weeks) when the pc was on, before i noticed it. But I had been checking the temperature whilst the blue scfreens were ocurring and I did not see anythiin suspcous - usually the cpu temp was about 40 degrees celsius.

The Heatsink I have is maden of copper and is rather large, and the rear case fan behind it is very close, which could possible explain the reason why the pc may have been able to run without the cpu fan working.

On opening the case, and removing the heat sink, I also noticed that on the base of the heatsink, where it is contact with the cpu, there was sone black residue. I doubt it, but I have been told it could be copper oxide. The residue was very minute and looked more like dirt, and the "splodge" of this black residue was not very big.

After trying to repair windows - using the xp cd repair function - windows failed to load (but the pc was still turning on). So, we tried to remove the hard drive and palce it into another computer. This was before we realised that one HD was SATA and the other IDE! Once we put the HD back in, the PC would no longer start.

HOWEVER, on my ASUS A8N-SLI PREMIUM MOTHERBOARD, when the power supply is plugged in, a green light does appear on the motherboard. Apart from that, there is no output from the pc - no fans turn on...nothing.I have even ditched clicking the switch on the outside of the case, and touching the two power pins together.

This happened in June, but as I had my GCSE's, I was unable to recitfy the problem at the time.

So the question I have - sorry for the long explanation - is why isnt it turning on! I have a couploe of questions:
can i pc turn on if the processor is broken?
can a pc turn on if the HD is broken?
could it be the PSU?
could t be then motherboard, even though a green light appears when power is connected to it ie the PSU is plugged into it?

I would appreciate any help on how i could diagnose the broken parts, or any other remedies anyone may have.

and sorry for such a long email!

  Giant68 04:41 03 Aug 2007

I think that the thing to do is to remove everything bar the RAM and graphics card, thats HDD, sound card etc, and try and turn it on. If the mobo is ok it should still go through the POST checks and tell you that it can't find a system disc. This will tell you that the mobo is ok so the problem is elsewhere. Then add components one at a time booting up each time until it fails, this will tell you which bit of hardware is knackered. If it won't boot in the first place and you have 2 sticks of RAM, try it with just one, then swap to the other stick if that doesn't work. The green light on the mobo suggests that the power supply is ok.


  Taff™ 06:09 03 Aug 2007

All good suggestions from Giant68 so here`s a couple more. Before you do anything try taking out the CMOS battery for 10 minutes, this will clear the CMOS. (Better still replace it with a new one) I would definately suspect the PSU. The green light on the Mobo doesn`t necessarily prove anything. Can you try a different one?

  keef66 09:59 03 Aug 2007

the green light suggests the green light's OK. The PSU could easily be knackered and cause the symptoms you describe.

If you can borrow a known working PSU that'd be the first thing I'd check

  skaria 13:48 03 Aug 2007

thank you everyone for your wuick responses.

I have tried to boot with just the ram and gfx card installed, and the pc still doesn't turn on.
I have also tried to remove the cmos battery and clear the cmos using the jumper, and tried a new battery - still to no avail.

I shall try and borrow a working psu from a friend and post back results asap!


  skaria 20:24 04 Aug 2007

Dear all,

I have the results:

I did as you guys said and tested my PC using a working PSU using a friends identically built pc. With this PSU installed, the PC still did not boot.

After this is tried to power up his PC using my PSU -his PC did not boot.


Moreover, when I reconnected his power supply to his pc ==> HIS PC DID NOT WORK - it had the identical problems that my PC has - it would not turn on!

SO, I'm not quite sure what conclusions to draw from this. The theory I have come up with is when I plugged his PSU into my PC, my motherboard sent a surge of energy to his PSU breaking it, which meant that he could not power up his PC using his PSU ==> a bit far-fetched, but I'm not sure what's going on!

Does anybody know what conclusions I can draw from this - is it my motherboard, or my PSU or something else - and why does his PC now have the same problem as mine. hmmm??


  skaria 20:35 05 Aug 2007

do you think i should send off both the PSU and motherboard for repair as tey are both under warranty?

also, does anyone have any cocnlusions that they are able to draw from yesterdays resutls?


  octal 21:27 05 Aug 2007

I would say it's something on your Motherboard blowing the power supply, you've taken you friends PSU which was working and put into you computer on returning it to your friends computer it doesn't work, so you've got two blown PUS's and one suspect Motherboard, yours.

Have you checked to make sure there are no short circuits, particularly around the mounting pillars.

  skaria 22:05 05 Aug 2007


thank you for your response.

sorry if this question is a bit stupid, but how to i go about checking if there are any short circuits (this is the first pc ive ever built).

Thank You

  octal 23:06 05 Aug 2007

To be honest I was about to reply with quite a long post, but after reading your first post again it seems as if the problem started when you removed the HD and re-fitted it.

Qoute: "So, we tried to remove the hard drive and palce it into another computer. This was before we realised that one HD was SATA and the other IDE! Once we put the HD back in, the PC would no longer start."

To answer one of your questions about being able to turn a PC with a broken HD, yes you can, but it will end up telling you that it can't find an operating system. I used this computer for about a week without a hard drive, just using a Linux live CD until I sorted out the HD.

I don't really know what to suggest at the moment because you could end up chasing your tail around and around trying to fault find something like this.

  skaria 23:22 05 Aug 2007

Thanks for that Octal. I understand what you mean. Ive been told to take the mobo out of the case and put it on an anti-static mat and then test it, so I'll let you know the results.

Thanks again,

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