Help ---&gt; Dead Motherboard or Dead PSU ?

Only boot when flat --> only time I've seen that occur, CPU retention bracket was broken and CPU heat sink would make sufficient contact when PC was lying on its side. Was a Dell PC and only had a heat sink attached to retention module. Didn't notice at first due to fan shroud covering heat sink.

Easiest way to tell is swap PSUs. But before doing any more troubleshooting, disconnect anything not required for a basic boot. Should be left with mobo, CPU, memory, video card (if not integrated) , PSU, and keyboard. Everything else removed/disconnected completely (power and signal leads).

09.17.2006 at 12:36PM PDT, ID: 17539243

Rank: Genius

Your history of problems with the motherboard ("... the first bios has been failing for some time ...") suggests that's the problem.

... however, the "... dodgy frazzeled smell ..." sounds more like the power supply, although the motherboard could have also been responsible for that.

I would give the motherboard a VERY close inspection with a flashlight and magnifying glass to see if there are any leaking or bulging capacitors, and if there are any signs of burned components. But the easiest component to replace is clearly the power supply => I'd try that first. I'd recommend a high quality non-modular (the connections on a modular supply can cause issues) supply: either a Seasonic or a PC Power & Cooling. This would be a good choice: http://www.newegg.com/Product/Product.asp?Item=N82E16817151025

09.17.2006 at 12:43PM PDT, ID: 17539258

Rank: Sage

Re: first BIOS failure. Have you copied backup BIOS to main BIOS? Appears to be a Gigabyte dual BIOS mobo. Purpose of dual BIOS is to be able to boot and/or restore if main BIOS becomes corrupt.

Gary (Seasonic) Case rides again ;>) They are excellent power supplies.

09.17.2006 at 12:58PM PDT, ID: 17539292

Thanks for the early comments guys, I have restored and upgraded the main bios many times, without effect, I wondered if the initial load on the PSU might cause it to go to second bios, prehaphs more so if the PSU was going ... is this likely ?

"the easiest component to replace is clearly the power supply => I'd try that first. " my thoughts exactly.

As far as I can see the CPU is in correctly - surely the motherboard should beep if it wasnt ?

Anyone got an idea why the power might come on of its own accord ?

I will look over the motherboard and report back tommorrow !

09.17.2006 at 01:05PM PDT, ID: 17539316

Rank: Genius

"... Anyone got an idea why the power might come on of its own accord ? " ==> Hard to say with any certainty, but either a failed motherboard (which fails to hold the power supply control line) or a failed power supply (which fails to respond to the control) could explain this. Does the power supply turn on when you apply power if it's disconnected from the motherboard ??

Accepted Solution

09.17.2006 at 01:15PM PDT, ID: 17539369

neutron7:

it could just be the fan that does not work which blew, causing the smell. and it is shorted out, causing the fan speed controller to have trouble with the other fan.and too much power draw for the board to boot properly.

09.17.2006 at 01:26PM PDT, ID: 17539434

Rank: Sage

Based on a reasonable amount of experience with such --> Most of the time it's a motherboard issue involving bad capacitors in the power circuit. Your board is too new for the "bad cap" era, but even good quality caps can and do fail. Have also seen same symptoms caused by a faulty power supply (usually caused by a failed cap in the power supply itself).

One other possible cause is a failed CPU. Take a close look at CPU HSF and ensure it is seated properly.

"surely the motherboard should beep if it wasnt ?" Nope, not necessarily. You have to enter POST for beep codes and you most likely aren't getting that far.

Assisted Solution

09.18.2006 at 07:13AM PDT, ID: 17543642

Thanks for all the help thus far,

"Does the power supply turn on when you apply power if it's disconnected from the motherboard ??"

Yes it does turn on - i disconnected everything bar a molex with a few (2) fans on it and it still turned on as soon as it was on at the wall (I also tried a new power lead - same thing happened) When it turned itself on the lights inside the PSU (it has flashy blue lights - looks good in a blue case :) ) were constantly diming and brightening

CPU HSF seem to be quite firmly seated ...

"I would give the motherboard a VERY close inspection with a flashlight and magnifying glass to see if there are any leaking or bulging capacitors," no magnifying glass but with a torch I didnt see any dodgy capacitors

I'm begining to think that its a dead/dieing PSU anyone agree ? or are there any other tests I can try before I buy a new one? Can anyone find anything on Hiper's returns policy - its meant to have a 3 year warrenty but I can find no further details on this

David

09.18.2006 at 07:19AM PDT, ID: 17543682

Rank: Sage

Can you borrow a PSU from another PC or a friend to test with?

09.18.2006 at 07:25AM PDT, ID: 17543725

neutron7:

If the LEDs inside are dimming /flickering then the PSU is almost definately kaput!

think of the LEDs as voltage indicators. bright = good dim = bad
no PC could run on a power supply that fluctuates like that.

sounds like the power supply has failed in an unusual way, but still failed.

Assisted Solution

09.18.2006 at 07:42AM PDT, ID: 17543858

Rank: Genius

Definitely sounds like the power supply => I would certainly replace it first. Unless you get it replaced under warranty, the Seasonic I linked to above is an excellent unit. But if you don't want to spring for that good of a unit, this is a nice unit for less: http://www.newegg.com/Product/Product.asp?Item=N82E16817103931

09.19.2006 at 07:03AM PDT, ID: 17551949

Thanks for the help all - I have a 500W Seasonic PSU on order
(http://www.scan.co.uk/Products/ProductInfo.asp?WebProductID=256337 )
2 days till it arrives, if all is well I'll divide up the points then

How many devices should be daisy chained on a Molex ? I have 3 hard drivers, which i used to put on one Molex, 2 CD drivers and a floppy when on another and a third cable was used for case fans ... leaving one spare - would i have been overloading anything?

09.19.2006 at 07:37AM PDT, ID: 17552251

Rank: Sage

The molex connector is the plug itself. If you were using Y splitters, then you may have overloaded a single connector. If you used 3 molex plugs on same power supply leg of PSU (set of wires), should not be a problem.

Your new PSU will have sufficient connectors. Old PSU was marginal at best and probably overloaded.

09.19.2006 at 08:45AM PDT, ID: 17552990

Rank: Genius

As willcomp noted, as long as you're using the connectors from the power supply you'll be fine. They're designed to handle the current demands for the number of connectors that are on any given leg. In general, you should avoid using y splitters -> and certainly do not use multiple splitters on the same power leg.

Your new supply is an excellent unit (as you've probably gathered, I'm a big fan of using top-quality power supplies); so it will certainly rule out power as the issue. I suspect you'll also be (pleasantly) surprised at how quiet the unit is :-) Your symptoms tend to indicate that was the most likely cause [especially the fact that your old unit (a) turns on by itself even when not connected to the motherboard; and (b) does not have a functioning fan]; but your previous issues with the motherboard (BIOS problems) may also indicate a problem there. ... but you'll know for sure in two days :-)

09.22.2006 at 04:46AM PDT, ID: 17576791

Hi All,

The new power supply arrived yesterday, it was a lot of 'fun' trying to replace all the connections (I wish I had smaller hands!) but it is in, and the computer is now working well :)

The only strange thing is that when I ask the computer to turn off, it turns off, then waits for 3-4 seconds - and then boots up again. ?! I can only guess that either the switch is broken or that the BIOS needs updating (guna look at this next! )... Its not a major enough problem to justify a new board though!

Looking at this non-modular PSU, I see what you mean with using Y-splitters, (I used none this time), The old PSU had just 4 direct connections, then bundled a load of splitters, I dont believe I had more than 3 devices per leg, but perhaps I did, causing overloading, though nowhere in the manual of the PSU did it give any advice on this!

Also the new PSU has an 8pin 12V cpu lead where as the previous one only had a 4pin lead, the motherboard manual said that this was ok with my CPU (Pentium D 830) but the next CPU model up (Pentium D 840) would need an 8pin, so to be on the safe side I am now using an 8pin connector ... again something small that might have affected the power supply I guess.

Anyway now to divide points, Thanks to all who've helped on this one,

Most points must go to garycase for "Does the power supply turn on when you apply power if it's disconnected from the motherboard??" Which cracked this one?

Thanks Again

David

09.22.2006 at 07:22AM PDT, ID: 17577757

Rank: Genius

Glad it's working. The automatic turn-on may be due to faulty capacitors on the motherboard (give it a close inspection with a flashlight to see if there are any bulging or leaking capacitors); or may be because you have something in the BIOS set to "Wake on ..." mode => "Wake on LAN", "Wake on Ring", etc. Check the BIOS power management section to see if there's anything that might explain the power-on.

09.22.2006 at 09:28AM PDT, ID: 17578737

Rank: Sage