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MSI 790FX-GD70 MOSFET failed ???

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February 22, 2011 3:42:58 PM

I'm currently doing a new build...or I was untill I began over clocking the MSI 790FX-GD70 motherboard. I had read on overclockers web that using Auto Over Clock did a good job. I am building this rig to sell and have no need to max over clock the cpu. Thought I'd see what result the Auto gave me. Here is the build components:

MSI 790FX-GD70 motherboard

AMD Phenom II X4 970 3.50 GHz Processor

Antec 850w Power Supply

Two XFX ATI Radeon HD 5770 in SLi Config.

8GB G.SKILL Ripjaws Series DDR3 1600 (PC3 12800)

Anyways, I had it all together and installed Windows 7 64bit OPS. Clicked on the ....I think it was AMD's Auto OverClock and went to the other room. I then heard the fan alarm. Upon returing I found my system powered off. When I pushed the Front panel power button all I got was a flash from my fans and MOBO leds. I began trouble shooting. What I found was that it's the 4 pin 12v CPU connecton on the motherboard. When I unplugged it, I would get the motherboard to run fans and the leds. When I plug it back in, I get the quick flash and nothing. I removed the motherboard to see if anything was grounding, check my standoffs and all was well. The motherboard showed no signs of damage. Checked my CPU all looks new.

I contacted MSI and they are going to replace the board....Don't even know if I want another one. After researching I have come to believe that it is an MSI motherboard problem.

My question to any and all is have any of you had this problem with MSI and MOSFET failure?

Do you believe it is a MOSFET Failure?

Do you think I could have fried my CPU as well?

I'm just worried that it was something else and a motherboard replacement is not going to resolve the problem.
I do not have access to another MOBO with an AM3 Socket...so I can't test. Just need insight from someone that may have had this problem themselves....Thanks, Randy.

a b V Motherboard
February 24, 2011 1:32:13 AM

I would think it is probably the CPU voltage regulator, which the motherboard replacement would solve.

My reasons? As it only occurs when the 4-pin CPU power connector is plugged in, and that only connects to the voltage regulator, it would be a problem with either the VR or CPU. Because of the way it shuts off, I would suspect a short, which would only really be in the VR rather than the CPU.
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February 26, 2011 5:37:54 PM

Thanks for the input...MSI now has the motherboard and I believe they are going to replace it. I guess I just have to wait for the replacement and fire it up....
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August 30, 2011 10:00:54 AM

This was absolutely a MOSFET/Voltage Regulator problem !

I have Phenom II x6 1055T with 790FX GD70. I wanted to overclock it to 4Ghz. At first apply I set the vCore to 1.38v, system booted and failed with BSOD. And then I increased vCore to 1.42v, this resulted a successfull boot. Temperatures were fine as CPU was cooled by Corsair H70. I used some benchmark softwares like wprime, sandra, cinebench. Everything was fine till I used Prime95, after about 7 minutes system crashed. But doing so did not make any damage to my mobo.

After prime95 crash I was thinking that the vCore I set is not enough for a 4Ghz overclock. Now I set the vCore to 1.45volts (Maximum safe range by AMD). System started successfully. Now again its time to run a burn test of CPU.

After about 12minutes with Prime95, system crashed again. This time the only difference from previous crash was that my system was not starting again. When I switched the power on, all LEDs including FANs were ok except CPU. FF was continuously displayed on debug LED. I reset the BIOS many times but nothing happened :( 

Now I clearly understood this was a serious injury. I killed my motherboard :( 

After searching through internet I found a review that helped me to understand what the exact problem was. And the problem was a Voltage Regulator/MOSFET failure. You can see it here:

http://www.legitreviews.com/article/1004/6/

I had immediately contacted to legitreviews and they replied that the first launched 790FX GD70s had some buggy MOSFETs that were not able to hold upto higher voltage. Unfortunately :(  I and you bought exactly one of them. I wanted to compare my MOSFET to their MOSFET and then I detached Dr. MOS and saw that the model no carved of my 790FX GD70's MOSFET (RENESAS 9A2S292 Japan) was exactly same as the one that the burned during testing (RENESAS 9A2S292 Japan). http://www.legitreviews.com/images/reviews/1004/msi_790...

I sent my dead :(  mobo for RMA. After 45 days they replaced with new mobo. I was so afraid of increasing vCore that I couldn't stop me to see again the voltage regulator model no of my new/replaced mobo. I saw some changes with numbers. The old MOSFET (Dead mobo) had 9A2S292 Japan written on it...........but now on new MOSFET it was 9A2S294 Japan. This made me very happy :)  as I was with new MOSFET.

But I am still afraid of setting vcore to 1.45volts :x

Thanks for listening.......and forgive my English coz I am learning :) 
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