Non booting PC, repair/transplant query

  Roadgiant 17:18 16 Dec 2007

My son’s computer will not boot up at all, working fine Fri night, turned on Sat am and the following.
On turning on the power the PSU & processor fans both spin, the DVD burner LED illuminates, USB mouse lights up and the power LED illuminates.
The keyboard LEDs do not come on, there are no beeps and the monitor displays says there is no signal.
The hard drive is OK (I have a external case that I have put it into and it is fine when I plug it into another PC and have retrieved some important docs)
The good news is that I was given his PC along with an identical spare PC (same motherboard Asus A7N8X with Athlon 2500).
When I was given these PC’s there was no DVD drive or op system, I purchased an OEM version of XP along with a DVD burner and installed them into one of the cases and also swapped graphic card and a few months ago swapped power supply after the original one failed.

I have never actually built a PC although as mentioned above have swapped bits and pieces around.
I suspect rightly or wrongly that it is either the motherboard or processor?
Is the easiest option going to be to swap the motherboard complete with processor from the second PC into the non working one and if I do that will XP work Ok (bearing in mind it is still installed on the hard drive?
Hope this is enough background for people to give me advice on how to proceed, thanks in advance for any assistance.

  PalaeoBill 17:35 16 Dec 2007

If you have never done it before, fitting a motherboard into a case can be very difficult. If fitted incorrectly you can cause a short circut, flex the board and crack it... You do have the advantage that the cases and boards are identical so the brass pillars in the case will align with the screw holes in the motherboard and the plastic standoff pillars on the boards will be in the right place. Even so, I would err on the side of caution and move all of the components from the dead PC to the living one, leaving the motherboards where they are.
XP will be fine, the boards are identical so it shouldn't give a peep. Even if they were not, XP would just declare that it had found new hardware and search for/install new drivers.
Do wear an antistatic wrist strap when you move stuff, especially the ram. If you don't have one, any old length of electrical cable/speaker wire will do (strip one end and wrap it round your wrist, strip the other and wrap it around bare copperwork like a radiator or water pipe).

  PalaeoBill 17:40 16 Dec 2007

Just disconnect the DVD and any other boards etc, before doing a transplant (To ensure its not one of them dragging down the PSU and preventing boot).
Then put the working PSU into the PC with the good MB and make sure you can power up and get POST (as it could still be a faulty PSU).

  Diemmess 17:45 16 Dec 2007

A few ideas chucked back to you.

No keyboard lights
Try substitute keyboard but if this doesn't work either, suspect mobo failure.

Try minimal load on PSU
Disconnect even the power to the HD (Which you know is OK), computer should boot as far as no Operating system found.

Failing that test - possible PSU failure (you have already had one dead replaced from the other twin computer).

Transplant the mobo to the other computer.
Major job but should work unless the surviving PSU is wonky .

If you do this there may be activation troubles but at least they are surmountable once you have a clear idea of what has actually expired.

You could put the PSU back in the cannibalised PC and see if it works there.

  Roadgiant 17:59 16 Dec 2007

Thanks for the fast replies,will work on it over the next few days and try the suggestions, fortunately we also have a laptop as well as my computer that I am using at the moment.
Just one query before I start transplanting if the PSU is faulty is it likely to that a PSU could only partially fail rather than completely die?

  PalaeoBill 18:14 16 Dec 2007

Yes, absolutely. They can pop their clogs spectacularly with the loud bang, blue flash and bad smell right through to they look like they are working but give no voltage out.
It is quite common for a poorly PSU to fail as you increase the load on it, or for a perfectly good PSU to shut down when you plug a poorly device like a DVD with a fault. The only way to know for sure is to unplug everything then start plugging it all back in again.

  Roadgiant 20:32 18 Dec 2007

Thanks once again for the help and advice, PC up and running.I sucessfully transferred everything onto the spare case with the motherboard and processor already in it.
I assume it was either the processor or the motherboard that suddenly decided to give up the ghost,is there anyway (without reassembling the old unit!!)of telling which item failed? Or is the best thing to do just dispose of both of them and if I ever have another problem worry about it then.
By the way I did not even have to re register XP even though it was a different m/board with the same H/drive.
I'll leave the topic open for a couple of days for any comments and then mark it resolved.
Thanks RG

  PalaeoBill 21:25 19 Dec 2007

It is unlikely that you will be able to see anything. The smell is generally the give away, electrical components give off a unique odour (something like but not the same as buring rubber).
But if you want to have a look at the suspect dead MB. When capacitors die they have a tendency to swell up. Solder joints can break if they were not made properly, look around the areas where the MB is stressed like the PCI slots etc. Are any of the components loose in a joint? Dry solder joints (they look dull grey rather than shiny silver) can work for a long time before failing (heat up/cool down cycle). Are there any dry solder joints? Do any of the ICS look burned/melted or has the printed text on them become distorted?
The only sure file way would be to swap the processor out. A dead MB could blow a good CPU so it would be better to try the CPU from the dead PC in the live PC's MB. I have never heard of a blown CPU taking out a working MB, but it is your call.

  Strawballs 22:27 19 Dec 2007

If the motherboard and CPU were the same as the other ones then you will not have to re-register as the windows thinks it is in the same system.

  Roadgiant 22:31 19 Dec 2007

Thanks for the reply, I think I'll call it day and get rid of them both and keep my fingers crossed and hope nothing else fails.

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