Another PC problem - any ideas?

[ehasler]

OK, having diagnosed a dead motherboard on my previous PC which had been the bane of my life for the last 6 months (now dismantled and sold on ebay/sent back under warranty/used to upgrade my other PC), I decided to go for something quiet and small, with a reasonable amount of power, so ordered the following:

Shuttle SN25P barebones system
XFX 7800 GT graphics card
AMD X2 4800 CPU
2GB RAM
3 x HDD (1 x WD Raptor, 2 x Seagate 400GB)
DVD writer

I fitted everything together, and fired it up to install XP. It worked perfectly, although the XP install didn't look complete, so I tried again the next day.

Unfortunatley, when I pressed the power switch the following evening, it refused to even switch on and just spun the fans for a moment before dying and a red "Over Temp" LED lit up on the motherboard.

For some reason, I decided to unplug the secondary power connector on the graphics card and tried again - it worked. I then plugged the cable back in while the system was running, and it stayed up and it even turned off and back on a few times quite happily, however on about the 3rd go it refused to start. I then removed the graphics card and it still refused to start so assumed it was the motherboard, PSU or CPU.

This morning I tried again without the graphics card fitted, and it still didn't start, however this evening it did start up with graphics card fitted (without 2nd power lead connected).

I've even tried unplugging everything except the graphics card and CPU, and it still doesn't run, so I think that rules out insufficient power (PSU is 350W).

So... it looks like a faulty graphics card, but why would the PC still fail to start even with the card removed? Could a faulty motherboard/PSU cause this - maybe a short on the secondary power supply to the graphics card?

This is making me so any help would be appreciated!

If it doesn't work soon, it's going to die a slow painful death

[mattley]

Hmm. OK, new build, Overheat error from BIOS, Huge processing power in a small box.....


1st thing is to make sure that isn't just a cooling problem. Check the Heatsink is properly seated, thermal paste applied OK and all fans spinning properly. Turn it on with the case off, and see if anything inside is getting too hot to touch.


The next most likely is a PSU problem. 3 HDDs spinning up and a very high power Graphics card can cause voltage instability, which would normally be within operating range but can affect the reference voltage the sensors need so they go into a fail safe fault state.

I've seen this quite a bit lately, and now buy decent PSU's, it's not just about the wattage these days



If I wanted a piece of kit where the sensors caused more faults than the kit they were sensing I'd drive a BMW.

[ehasler]

The over heat LED comes on straight away, when the CPU is still cold, so it's not an airflow/over heating issue.

I've tried it with all 3 HDD drives disconnected and RAM removed, so I think that would rule out power supply as it still fails to start, although it is inconsistent - there isn't one configuration that always works or fails to work 100% of the time, which is making it tricky to troubleshoot...

Actually - I've just tried removing the CPU, and it started up every time, even with the graphics card plugged into both sockets. Plug the CPU back in (with graphics card removed completely), and it sometimes works, and sometimes doesn't...

So... No CPU, and graphics card fully powered - PC works
Add CPU, and it doesn't work
Unplug graphics card power lead, and it works again (usually).

Faulty CPU maybe?

[silverfox]

Long shot - is the Integrated Cooling Engine (ICE) on that system working/plugged in as expected?

Sort of sounds like the processor cooling might not be reporting it's happy, so the system gets shut down seemingly at random.

Maybe?

[mattley]

ehasler said:

Faulty CPU maybe?

Not necessarily faulty as such, just sub standard, for the rest of your system.

[pdV6]

ehasler said:

The over heat LED comes on straight away, when the CPU is still cold, so it's not an airflow/over heating issue.

Ah, but if you have a heatsink fitted to it, how would you know the CPU's cold? If the heatsink isn't conducting heat away from the CPU, the CPU will rapidly overheat and the heatsink won't necessarily feel hot...

...but the rest of the symptoms you describe do tend to imply a power issue; I'd still be worried about the motherboard LED lighting, though, unless its a dual-purpose warning light?

>> Edited by pdV6 on Thursday 17th November 09:36

[Plotloss]

Cooling is my first thought and as AMD chips dont have overheat protection I am thinking like Pete, unseated heatsink.

[Munter]

Plotloss said:

Cooling is my first thought and as AMD chips dont have overheat protection I am thinking like Pete, unseated heatsink.

But he had left the PC shutdown for a good few hours and it wouldn't boot. So it should have been cold to start and then overheated if it's a cooling problem. Not when cold it wont boot unless you remove some of the power drain by disconnecting the extra power to the graphics.

My suspicion is the PSU. Can you unplug all but the 1 HDD with XP on it and leave the graphics card plugged in?

[Munter]

ehasler said:

I've even tried unplugging everything except the graphics card and CPU, and it still doesn't run, so I think that rules out insufficient power (PSU is 350W).

Ah ok so ignore my its the PSU suspicion then...doh! (Read the post Munter!)

ehasler said:

So... it looks like a faulty graphics card, but why would the PC still fail to start even with the card removed?

Did you get a beep code when you did this? I know none of our work systems will boot without a graphics card. But they do give a beep code.

[Plotloss]

Unless it fried on first power up, then the symptoms on reboot are consistent.

Tricky one.

Power or cooling though.

Whats the wattage of that little Shuttle PSU?

[Munter]

Plotloss said:

Whats the wattage of that little Shuttle PSU?

ehasler said:

I've even tried unplugging everything except the graphics card and CPU, and it still doesn't run, so I think that rules out insufficient power (PSU is 350W).

[Plotloss]

Possible.

One should not underestimate the power draw of these new fangled hulking 3D cards...

Ed, got another VGA card you can test with?

[ehasler]

pdV6 said:

Ah, but if you have a heatsink fitted to it, how would you know the CPU's cold?

I took the heatsink off, and tried to start the system. If it started, I switched it off again after a couple of seconds, so the CPU never got more than warm to the touch.

I tried again this morning with all HDD drives and DVD disconnected:

1) CPU, graphics card (2nd power connecter disconnected) and 1 stick of memory fitted in slot 1 - FAIL
2) Remove graphics card (so just CPU and 1 RAM stick fitted) - FAIL
3) Remove RAM so just CPU fitted - FAIL
4) Remove CPU - WORKS (power comes on and fans spin)
5) Refit CPU - FAIL

Previously, some of the above combinations have worked (e.g., combo 1 worked last night) so it's very inconsistent. The only two combinations which have always given the same results (except day 1, where it powered on with everything fitted) are:

1) Everything fitted and graphics card connected to external power connector - FAIL
2) Everything including CPU removed - WORKS

I assume the "Over temp" LED has a dual meaning, but I can't find out what else it means...

[flossythepig]

Just a thought but has the BIOS been updated to cope with the X2 processor? If not you never knaow what it is trying to do.

Hugh