PSU faulty under load?

[Guest]

I have a thermaltake toughpower 750W PSU, advertised as 4 x 12V rails.
My computer has an AMD 9950 Black and an ATI 4870, and nothing else fancy.

I recently had a problem (http://www.tomshardware.co.uk/forum/257516-15-smoking-memories-incandescent), when, while using folding@home, after a little while, the computer would shutdown. It would not start again until the PSU was unplugged and replugged (standard PSU safeguard, I believe). However, uppon restarting (several hours later), my graphics card fried (smoke and everything).

The next day, it was working again, but my graphics card completly fried the day after that, after the same shut-down problem.

I sent the card back in for RMA, and will be getting a new one shortly (I hope).

I'm wondering if my PSU is faulty. I've heard that if the PSU gets hot, its power output goes down, and it can fail to power the computer. However, the shuting-down is a fail safe that prevents damage, before anything serious happens, right?

My PSU has a 12" bottom mounted fan, but my antec p180 case has the PSU bottom mounted, so there is only about 1/2 an inch under it. Do you think I over heated my PSU, leading to a power problem? There is a fan that is blowing air onto the PSU, but at min speed. Should I increase the speed? Do you think I have an air cooling problem?

I know the PSU can power my system, but I wonder how good it can do it prolonged under max load...

Also, the PSU claims to have 4 rails. How can I know how they are divided on my cables? How can I be sure my rails are correctly divided (especially with my 2*6 pin PCI-e card)

 

[Guest]

Sorry to double post, but I couldn't find the edit button.
Here is the PSU pecs: http://www.thermaltakeusa.com/Product.aspx?C=1264&ID=1508#Tab0

 

[mythor20]

The opening under the PSU should be facing up recieving air from the bottom of your case, 750w should not have ANY problems running your system with your specs.

You say you only have half an inch under the PSU? Can you not turn your PSU upside down to allow the PSU to receive air from the top of it instead of the bottom of the case still blowing air out the back of your case?

Your GPU when it fried, possibly damaged your PSU although it shouldn't with the PSU's overcurrent protection? Have you tried another PSU?

 

[mythor20]

Look at the specifications of your PSU, the 12V rails should be rated at a specific amperes (amps(A)).

There is a sticker (should be) on the side of your PSU, each rail named 1 to 4 should be labelled, then simply decipher that with your 4 12V outputs.

Does this make sense?

 

[Guest]

I can't flip over the PSU because there is no air intake over the PSU in my case. I'm going to try to switch some fans around, and clear up some clutter, so there is a better airflow.

According to the specs page, all four +12V rails (12V1 to 12V4) have 18A limits, with a combined maximum of 60 Amps. Other than that, it doesn't say much.
I suppose the 12V1 is used exclusivelly for the ATX power supply, but what about the other 3? I have a quad core CPU, and my GPU reauires 2 PCI-e connections. If even one of these share the same rail, won't that be problematic.

I'm also worried that if the system works correctly, that under full load, if some rails are shared, I'm flirting with the 18 Amp limit, thus causing a power failure if the PSU gets a bit hot, or if an un-expected power demand arrives from somewhere else (DVD drive spinning up or something)

Am I worrying over nothing?

 

[mike99]

Install Speedfan and monitor the 12V supply with the Chart Tab, see if it is unstable under load. Check the temp of the air from rear of PSU with back of your hand, can be warm, bot not HOT!

Mike.

 

[Guest]

I'll try that.

Does speed fan monitor the Amps on the 12V rails, or just the volts?

 

[evongugg]

Your symptoms are that of as failing power supply.

Anytime your PSU fries something, get rid of it. Don't take any chances.
You did the right thing to return it.

 

[Guest]

Actually, I returned the Graphics card, thus PSU is still in my system. The system works fine without the card.
I'm going to test the system with a garbage card tonight.

 

[RetiredChief]

I dought that you are maxing out any of your 12V rails. I have the 4870 card also. I also have 4 HDDs and the only difference is that I have a E6400 (OCed to 3.2 ) vs your 9950 Proc. My max Power consumption under full load is only about 320 Watts.

In refer to the 2 x 6 PCI-e connectors on the GPU - That is more of a issue of preventing overheating of the Connector pins than a current limiting issue (ie 12 x 18 = 216 Watts). As to which rails are which, 1) the PSU manual may Identify. 2) a good review (forgot the web site) may have. 3) Not the tracer color on the 12V wire as they tend to use a differerent color for each rail.

I would use CPUIDs Hardware monitor (Vs Speedfan) to monitor your rails as it displays bout nominal, min, and max voltage. None of the monitors displays current and only the 12V1 (to MB) is monitored.

What I would do is look at how much your +12V1 drops under load (ie run ATITools 3D view) and monitor the diff between max and Min. Your Min should not drop Below +11.5 V (Some say 11.3 V).

On PSU cooling - I also have my PSU located at the bottom whith the PSU drawing air from the "Floor". I set my Case on a piece of plywood for two reasons. 1) it tends to reduce dust buildup which can cause overheating. 2) If set on a carpet, the feet sink into the carpet thus reducing the clearence. Inaddition to placing the case on plywood, you can plce a 1/2 to 1 inch block under each of the four case feet.

PS excuse spelling and grammer error as they are not my strong points

Added: PSU vs GPU failure. You stated your GPU card "Fried". This may, or may not have been caused by the PSU. And Yes, if the initial problem was the GPU then it MAY have damaged, or weakend, your PSU - Some what like the question of which came first the chicken or the egg. Not sure of the ranking of your PSU (ie which tier it falls in), But even good PSU's fail. Most "Good" PSUs have good voltage/overcurrent protection - But very few have good undervoltage protection and undervoltage can cause overcurrent. If You do replace your PSU and you are concerned about current per rail you could look for a PSU with a single rail (only major disadvantage is that it allows excessive current per +12 V line if an overcurrent condition exist).

 

[Guest]

Thanks for your reply.

I'll try to monitor the using your app. According to my previous thread, the PSU wasn't faulty, as only the GPU was fried. However, I still have my doubts.
The PSU manual doesn't identify which connector is which rail. I'll try looking for reviews.
As for the PSU location, my case is completely sealed, with air intake coming from the front, with anti-dust filters. This means the bottom of the case is closed, so ply-wood or no ply-wood wouldn't change anything. But the case is designed for good airflow, so I think I should be fine.

I read a review about my card that it had good overvoltage protection, but bad undervoltage, so I hope I didn't damage it.

As I said, I'll try with a garbage card, and I'll keep the thread posted.

 

[RetiredChief]

I would mod your case by drilling a series of holes (approx 1/8 -> 3/16") on the bottom of your case under your PSU fan and add a filter. I know a lot of work as you have to remove PSU and MB. But it would reduce PSU temp as your cross (front to back) air flow does not provide good air flow at the bottom of the case. This would eliminate any question on good cool air to the PSU.