Computer won't boot - any ideas?

[hardflipman]

Hi,
my PC has started to stop booting. I'll set the scene a bit...

a while back I had problems with it where it would fail to boot into the windows GUI. Back then i tried changing graphics card, removing extra hdds and cd drives, removed some of the memory etc to no avail. tried a new hdd and a fresh install of windows and again it failed to boot into the GUI. now i was in the process of renovating the house so it just got left. once all the wiring had been changed etc and the house was livable i plugged it in and it worked fine. this was a week or two ago.

on saturday night i noticed that my squeezebox lost it's connection to the server (my PC) and i just assumed it had gone into standby. however on sunday morning i looked at the PC and just the HDD light was on, fans whirring away, no display etc. holding power button down for five seconds got it to go off and then it would not POST at all. no display, graphics card fan going at full blast. nothing i could would make it power on. so i removed all drives, changed the memory, swapped graphics cards to a 3650, reseated the cpu all to no avail. i then tried a low power PSU from a dell SFF machine and lo and beholdit POSTed. so i plugged the old PSU back in and it worked fine. for a few hours and then did exactly the same thing.

So my question is this. based on the above would you suspect it to be PSU or motherboard at fault? i'm going to try using the PC with the wee PSU but i'll need to put the 3650 in. and to be honest i still don't know if a 250 watt PSU wil be enough to power my machine...

my system is as follows: gigabyte p35 ds3r, pentium 2160, zalman cooler, 4x1gb corsair value ram, 2 x 500gb hdd, 2 dvd rom, x1950 pro graphics, antec p180 case, corsair 520watt modular PSU

just as an aside, i also kept recently getting windows mesages saying a device could operate faster if it was plugged into a usb2 port. i only have the hub from my dell monitor plugged in and a card reader connected internally. never used to get messages of that ilk...

help greatly appreciated

cheers

[da.Guvna]

Have you tried using the aforementioned PSUs in any other machines for an extended period of time?

If they hold up, I'd say the motherboard definitely sounds iffy...

[hardflipman]

cheers for the reply.
when i get the chance i'll swap PSU's with my wife's pc that way i can test both psu and motherboard at the same time. although the pc stayed on fine the other day with the 250watt psu so i'm leaning towards it being that. unless of course the pc works on it's side and not standing up!

[peterb]

As in a previous post, download memtest 86+ and use that to check the memory.

[hardflipman]

memory should be fine as i have used it my mums pc to find out that her memory was knackered!
but given that it does not POST then i wouldn't be able to check the memory. unless of course i tried it with the other PSU - hmmm
i'll get the chance to do some proper testing over the weekend

[zammozammo]

I would focus first on the PSU. Make sure that the two PCs have the same PSU connectors as they are not always the same in all PCs.

[hardflipman]

So, finally managed to get some testing done. swapped PSUs over and my wife's PC worked just fine. with some difficulty got the hiper type-r into or rather on top of my PC and left it on for a few hours. when i went back the HDD light was on and no display. PC would then fail to POST.
surely it has to be the motherboard?

[hardflipman]

So, lo and behold i took the motherboard out of my case and it seems to be absolutely fine sitting on my desk. was on for 5 hours yesterday with no problems. maybe it just doesn't like being vertical...

[piggin23]

Could you have a loss connection or a short against the case.
Would explain how it works outside the case.

[hardflipman]

well, thing is it does work in the case just not for very long. reseating power supply helps. what would happen if i didn't plug in the p4 opwer connector? wonder if that might be coming loose?

[piggin23]

If you did not connect the P4 the motherboard would not work.
Have you got a brake in a cable (cables can brake internally and when moved make a temporary connection)
Also you could have a poor soldered joint on the board that is losing a connection when it heats and expands.

[hardflipman]

I used 2 different PSUs so highly unlikely to be the cable. i'm definitely suspecting a dry joint or something that only happens when the motherboard is vertical

[piggin23]

If there is a dry joint on the motherboard then its time for a new one as the cost of repair is cost prohibitive (unless under warranty)

[hardflipman]

OK, so my pc stopped working again last night but this time i was actually trying to shut it down when first of all the mouse started stuttering then stopped working and the keyboard went a bit mental. then the usual inability to power it back up etc. i still need to get a hold of a speaker so i can listen for any diagnostic beeps