PC problem.

[Dave Plowman (News)]

Got a fault on the old ASUS desktop. Running Win7.

For ages at start up it has said CPU fan fault - but pressing F1 gets it going and it's fine afterwards. The CPU fan seem to run normally, and I tried replacing it.

But now, press the power button and it doesn't even get to the start up banner.

Main fans and CPU fan running, though. But not the PS one. Press and hold the reset button makes that run. Release and it stops.

Play around and it will sometimes boot but crashes soon afterwards.

Worth trying a new PS? Or would any fault in it be obvious?

[Martin Brown]

I suspect that with the reset button pressed the load on the PSU is minimal and it croaks as soon as it is required to do any work.

Might be worth seeing if you can boot it and see the PSU voltages in the advanced section of the BIOS or diagnostics (if they are provided).

Usually PSU's fail completely so that they blow an internal fuse or in one case I had the magic smoke and fan assisted sparks coming out the back. I unplugged it PDQ. Swapping the PSU is certainly worth a try.

[Dave Plowman (News)]

Vcore 1.40v

3.3 3.32 5 5.02 12 12.22

All from the bios page.

They all look OK to me - but not sure what Vcore should be.

[Brian Reay]

Have you tried reseating the memory, replacing the back up battery, checking any socketed devices are pushed home.

It is always worth vacuuming out the dust etc, especially from between heat sink fins, while you are in there.

I?ve recovered a surprising number of dead PCs with nothing more than the above.

[Andrew]

Maybe remove any additional PCI/(e) cards that are optional to reduce the loading and see what happens.

Doesn't it give a series of audible beeps that indicates what the fault could be ?.

Good time to upgrade to a 80+ PSU to save on leccy, assuming it is standard PSU size.

If the national voltage and frequency went down too low back in august, I wonder how many 'odd' failings are occuring all around the country with all manner of stuff.

[Martin Brown]

But not if the PSU itself goes into thermal shutdown under load.

Switched mode PSU's tolerate brownouts remarkably well. My recollection from the old days of tube based VDUs is that the monitor would fail to light up the screen before the PC stopped working when we did voltage tolerance tests on things expected to have a rough service life.

[Brian Gaff]

Have you checked the bios? I had a similar issue and a driver for the fan had vanished for some unknown reason. If the processor is overheating that fast though, could the processor be faulty or the thermal contact with the heat sinc be bad? Have you vacuumed out the heat sink? Brian

[Brian Gaff]

Yes also one dodgy stick of ram can make the pc shut down almost as soon as it comes on. Brian

[Michael Chare]

There can be duff capacitors in the PSU which cause problems like that.

[jeikppkywk]

That sort of quirky result is often due to bad caps on the motherboard. Easy to check by eye, look for electros with bulges on the top.

Very unusual for a bad PS to produce those symptoms, It can do but if it does, its usually due to the 12V supply being way out but that?s easy to check with a multimeter.

Not always but it wouldn?t normally produce those symptoms if it was the PS. The PS fan effect is unusual, measure the voltage its getting with the reset button being held in and when its released when the fan is going and when its not. A few systems do shut down if the PS fan can be seen to not be rotating,. but that?s uncommon.

[jeikppkywk]

It wont be the Vcore producing the PS fan effect.

[Commander Kinsey]

What is this voltage/frequency event you're referring to? In my experience you can't rely on the mains being solid at any time. After all, it's supplying thousands of houses in your area with loads changing all the time, you can't reasonably expect them to keep it perfectly stable. Any appliance you use must be able to accept some changes. I put my computer (and peripherals, and my house lighting) onto a UPS. Had zero problems since, plus the LED lights in my house last 4 times longer.

[Commander Kinsey]

Most computer PSUs I've used will shut off after a 1 second powercut. You really need a UPS.

[Commander Kinsey]

RAM is easily tested with a freeware self booting program called memtest. Faulty RAM usually causes blue screens.

[Commander Kinsey]

[Commander Kinsey]

Usually spottable as they bulge or burst. Same happens in LCD TVs.

[jeikppkywk]

More likely on the motherboard with the cpu fan warning tho.

[John Rumm]

It could be the RPM sensor is not working (either on the fan, or the logic for reading it on the motherboard. You may be able to change the fan type in the BIOS such that it does not expect it to be a three wire type.

That sounds more like a PSU problem.

That could be overheating - either CPU or PSU.

I would say its worth a try.

[Dave Plowman (News)]

The BIOS does give the fan RPM. If the tach signal failed, I'd expect that to be rubbish? But it looks a sensible speed to me.

I've ordered up a new one.

[jeikppkywk]

Maybe its just slow to start and that?s why hitting F1 sees it fine later.