PC shutdown issue, PSU -12v at -9.5V ?

[Dutchman]

Hi there

I recently posted in the general section about PC issues I've had:
http://forums.overclockers.co.uk/showthread.php?t=18062029
My PC Spec
Corsair HX 620W PSU ( bought from competitor )
8800gtx ( bought from OCUK in ages ago )
Phenom II x3 720 @ 3.4 ( bought from OCUK in Apr 2009 )
Gigabyte GA-MA790XT-UD4p MB ( bought from OCUK in Apr 2009 )
4GB Corsair XMS3 DDR3 TwinX memory ( bought from OCUK in Apr 2009 )
Sunbeam Core Contact cooler ( bought from OCUK in Apr 2009 )
1 x WD 250GB and 1 x WD 750GB Sata drives
DVDRW drive

Since then I've had my PC shutting down on me unexpectedly a few times already, twice in the past hour.
What's strange is viewing the sensors via SIW.exe, the -12v is reading between about -9.4 and -9.9V , is this indicative of the PSU being the issue.
I've searched the forum and a few tech sites but can't get too much info regarding what the -12v reading means.
Any ideas ?

 

[Dutchman]

Thanks for the comments and suggestion guys.
Sorry, I did omit quite a few things. I have already run thorough memtest on both my mem sticks, also been running without an overclock since the issue started, never overclocked my 8800gtx, it runs hot enough just on standard settings.
But I think it's a good idea to run it with just 1 mem stick, just 1hdd, no dvd, will give this a go over the weekend.

Haven't got a multimeter but starting to think it may be a good time to get one now. I saw a few websites actually showing how to test your various PSU readings using this, guess it's worth a go

 

[Dutchman]

Well, just when I think I'm making some progress in tracking down what's causing this I get thrown a curveball googly doosra.

As Suggested by Johnerz I took my system back to basics, 1hdd, 1stick ram, no dvd and it ran fine for 2 days doing pretty much the same things that had caused at at least 2 a day shutdowns. So I put the other stick memory back in and within about 5 minutes the PC shuts down.
Eureka, must be dodgy memory !
So I take out that stick of memory, put back the hdd and dvd and it runs fine for another 2 days. So today I decided to start putting some serious strain on the PC to see if all okay, running Prime95 and Furmark to stress CPu, mem and GPU. Prime95 started fine and the minute furmark started, shutdown. I power the system back up and run prime 95 and then furmark and this time it runs fine, gpu pushes 90 degrees after bout 10 minutes, left it another 20 and no issues. Then go to play a game of PES2009 and it shuts down 5 minutes into it.

So first I thought it was one bad stick of memory, then GPU then back to PSU.
I did log a support ticket with Corsair last week and they have come back and said that I should RMA my PSU. It's a starting point, but my concern is that I send it in, they find nothing wrong and send it back and I'm out £15+ shipping. Secondly, it'll leave me without a working PC till I get this back, unless I buy another PSU ?
Any thoughts ? I'm starting to lean towards buying new PSU, I'm a bit accident prone and have a feeling buying a multimeter and attempting PSU readings whilst the system is live and at load is going to leave either my system or me with some permanent damage

 

[Dutchman]

If probing with a multimeter puts anything at risk, well, even your hand is a greater threat to hardware if you remove anything. Not an exaggeration. (did you disconnect AC power cord from its receptacle before removing anything?) Get the meter. Stop entertaining fear. Get hard facts - numbers. Then have a useful reply in the next post.

Lol, yes I disconnect the AC power cord before doing any work in there, also ensure I'm not statically charged.

I'll have a look at high street store tomorrow for a multimeter. Best site I could find for showing how to test the psu with a multimeter is this:
http://pcsupport.about.com/od/toolsofthetrade/ht/power-supply-test-multimeter.htm

Is that okay or do you have a better guide ?
Also, will any multimeter do ?

 

[Dutchman]

whats the temps of your cpu?

Why buy a new PSU, when you can have your current one checked and if neccessary replaced for free at the cost of £15 PnP? You won't find a new PSU for £15, and if you do, don't touch it

I gather your CPU is overclocked, and that at one point you were seeing differing behavior between one stick of RAM and another. It may be that one of your sticks is bad, and you also have another issue, and I suspect it may be a lack of voltage for the RAM or Northbridge. What speed is the RAM running at after the overclock? Is it still in spec? If not have you tried underclocking the RAM before upping the CPU speed? It's been a long time since I tried to overclock an AMD system, but I should imagine that pushing up the hypertransport might require more northbridge power (Assuming that's how the OC was done, and not a clock multiplyer change).

CPU temp under load is about 29° C, at low usage it's around 22
Since issue started I've taken off overclock so it's running 2.8 standard, overclock was using only multiplyer change.
Hazardo - not that simple, as I would have to take the psu out and send it away, and from past experience RMA'ing stuff I'd be lucky to get it back in 3 weeks, so I'd have to be PCless for that time.

Westom - thanks for your input, I've got my newly bought trusty £14 multimeter and about to find out what voltages my PSU is pushing out ( or some other weird numbers ). Okay, actually I'm gonna have dinner, watch a bit of telly and then do it, If I'm not back by 10 please call Emergency services for me !

 

[Dutchman]

First get a significant load on the PSU - as large as you can without causing a crash. For example, play complex video graphics (ie a movie) while searching the hard drive, while downloading from the Internet, while playing a CD-Rom, while powering a USB device, while playing sound loudly, while ... Now the supply 'system' (not just a power supply) has sufficient loading for useful numbers.

Measure (and report with three significant digits) voltage on the purple wire where that wire connect to motherboard (push red probe inside the nylon connector - black probe connected to chassis).

Also measure voltage on the green and gray wires both before and when power switch is pressed. Report those numbers and behavior as switch is pressed. Do not get confused using that jumper. Do not disconnect the supply from motherboard. Do not disconnect or remove anything.

Measure voltages on any one of orange, red, and yellow wires as the power switch is pressed. Even if a voltage starts to rise, then falls to zero - report it. Even if nothing happens when the switch is pressed, still measure and report each voltage.

Measuring those voltages should take less than a minute. Report those three digit numbers here for analysis and to learn what you did.

Right, here we go
Purple on full load was 5.04 and remained constant. Ran video in background, played pes2009, plugged in all my usb devices ( 1 external hdd, 1 x 16gb memory stick, 1 webcam, usb wireless ), ripped dvd to hdd, not sure how much else I could do
GRay - 0 before, then went to 1.56 and then 3.87 within a second and remained there
Green - Weirdest thing, couldn't get a reading off this despite trying about 10 times and pressing in the test lead quite hard and from different angles
Orange - constant 3.39
Red - constant 5.04
Yellow - constant 12.08

From the pin outlay I can see that the 3.3,5 and 12v seems fine, but what's the green meant to be and is the gray within the right range ?

 

[Dutchman]

Thanks guys, I appreciate your time !

Let me just clarify my issue - my pc randomly shuts down. It doesn't BSOD or hang or crash, it's literally as if somebody has switched off the unit at the wall, no fans remain spinning and only way to get PC back is to turn it back on again.

Westom, I think I took your post very literally and as such only measured orange,red and yellow at startup and once windows had started I took it off, so it would've had 0 load.

Measure voltages on any one of orange, red, and yellow wires as the power switch is pressed. Even if a voltage starts to rise, then falls to zero - report it. Even if nothing happens when the switch is pressed, still measure and report each voltage.

Measuring those voltages should take less than a minute. Report those three digit numbers here for analysis and to learn what you did.

Less than a minute, took me nearly 30minutes, as my PC is between the wall and desk leg, I have to disconnect it and move it away to connect, and I constantly had to reread your post to ensure I get the right things measured.

To get full load I did this:
Ran video in background, played pes2009, plugged in all my usb devices ( 1 external hdd, 1 x 16gb memory stick, 1 webcam, usb wireless ), ripped dvd to hdd, not sure how much else I could do
I'll do the same and remeasure the orange,red,yellow and try to get something on that green cable, good to know what it should do as I thought it should be 0 and then rise, but much easier if I know it has to be around 2 and then drop when I power on

So, I guess it's back to the drawing board ( or measuring board ).

 

[Dutchman]

Okay, redid measurements and below is the results

Green - Was 4.92 prior to power turning on, after power on it drops to 0.02, so seems fine according to previous statements

Under load which I tried as before, but also did seperate readings under a load by running prime95 Large ffts and a 1920x1200 16xMSAA Furmark just to make sure
Orange - Startup, 3.39, under load, still 3.39
Red - startup 5.04. under load still 5.04
Yellow, startup 12.08, under load went got readings of 11.98 and 12.04.

I guess from the above that it seems it's not the PSU then.
Whilst doing this testing I did a visual inspection and couldn't find any bulging tops.

So from your items to tick off it kinda leves the CPU, GPU and MB ? All but one of the shutdowns I've had has happened whilst either gaming or running a gpu stress test, reckon I should start hairdrying it a bit and seeing if it goes, although Furmark pushed it to around 90 degrees and it was still fine.
For both GPU and CPU I can surely run burn in tools like prime and furmark for longer to see if this cause shutdown, but I feel this would still not definitely point to the culprit as the MB always comes into play.
You mentioned diagnostics, as mine is custom built I obviously don't have any, but we use Hp machines at work, could I get diagnostics for that that would work/test my system ?

What is strange is that during both today and yesterdays tests the PC didn't once shutdown, and that's makes this issues so frustrating is that I can't readily at will replicate the shutdown.

 

[Dutchman]

Cheers again for the comments and suggestions.
Plec, makes sense what you are saying and once finished here I'm gonna give that plug a wiggle and see what happens.

Weird_Dave, If I knew when it was shutting down I could run the test, but it's very random, and each time I have deliberately tried to get it to shutdown by running load and such nothing happens.

Westom, good point indeed, I've not even thought of checking PSU fan, most notably because my PSU is mounted fan down in an Antec p182, but may unscrew it and see what the fan is doing.

 

[Dutchman]

A defective connector would appear in the numbers. Simply measure voltage after the connector. If connector is intermittent, then that defect also appears on the meter as a voltage reduction. Observe a defective plug using the meter; even when connector is not causing failures today. Either voltage will always be lower, or the connector is not causing intermittents.

No reason to remove that fan. A tool, ears, and your hand should be sufficient to feel the fan working. A stick can be stuck into an 80 mm fan to stop it. Then see (hear) how quickly it restarts when released. A fan with sufficient torque will start quickly. A fan with reduced torque (defective) sometimes will not start or will start slowly.

Very useful as always, thanks Westom. I actually gave the plug a wiggle and nothing, also measured all yellows, orange and red cables again, still getting similar results to before.
I actually didn't mean I would remove the fan, just meant that my psu is mounted fan down and is at the bottom of the case, so I can't stick something in to stop the fan and see if it resumes spinning okay. I can feel a very faint bit of airflow coming out of the back, may need to see if this picks up under load.
I'm out tonight and working tomorrow but reckon Sunday I'll have a look at the PSU fan.

 

[Dutchman]

Dutch,
Your PSU has variable fan speed, so it may not spin as fast as you would normaly expect.
If the fan is spinning fast, don't shove a stick in to stop it as you can damage it, better to power on with the fan stopped by the stick.
Is there a gap between the fan and the bottom of the case?

Thanks, I'll do it that way rather than shoving in something after it's already running
There is a gap between the case and the PSU, haven't taken a photo myself but this one here is similar to my setup and shows the gap:
http://ups.imagup.com/04/1240549330_P1010018.jpg

I'm gonna test my PC intensively today( I'm gonna play games ! ) and do more troubleshooting tomorrow

James, thanks for the suggestion, if I don't get anywhere in next couple of days I will slum it and put the ATI 1950 for a few days