View Single Post
Old 06-01-2021, 07:36 PM   #11
master hoarder
momaka's Avatar
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 10,862
Default Re: Tesla m40 burned my motherboard VRM

Originally Posted by waldoalvarez00 View Post
Seems the memory VRM failed somehow, that is why L14 inductor is cracked and close shunt is also little bit bulged. Since it takes power from PCIex port that is what caused the motherboard VRM to burn.
I agree 100% with the video, but this is NOT why your motherboard's CPU VRM burned. The two are not connected in any way and it's just NOT possible.
I've connected many video cards with burned MOSFETs and inductors to motherboards (and even watched as one puffed a ton of magic smoke due to a single rail powerful PSU not shutting down when it should have), and in none of those cases the motherboard was damaged. The only exception is if RAM VRM on the GPU takes power from 12V rail from PCI-E connector - then you can get melted pins on PCI-E connector if PSU doesn't shut down and there is a severe overload there.

But regardless, motherboard's CPU VRM -cannot- be damaged by video card.

Whatever happened in your case, I can't say with 100% certainty because I don't have hardware in front of me. However, I am pretty certain of the above that motherboard wasn't damaged by your GPU.

That aside, of course the cracked inductor on your GPU probably should be addressed indeed. To me, that looks like a factory installation defect and not one from an overload. If it was overloaded, you would have seen some sooth and discoloration like the pictures in the video above. Your card doesn't have that and your R33 inductors look good. The fact that your card even booted to desktop means they are still working. Now, should you do a preemptive replacement of the R33 inductors so that your card doesn't fail? - That's up to you. But to me, it seems that your Tesla video card is working OK at the moment, and I again would strongly suggest you test it on another (older / less valuable) motherboard to confirm its operation. I think you will find that it works normally, and your AsRock z77 burned CPU VRM for some other (unknown) reason. (Though, like petehall347, I too don't like the looks of those long threaded rods and suspect foul play with the custom cooling you had on there.)

Originally Posted by waldoalvarez00 View Post
Is just a bad designs from nVidia. Not even a fuse there.
It's not a bad design. Just cheap construction for cost savings during manufacturing. The design is good.
They just used smaller inductors to save on part costs, regardless that this is an expensive GPU, which is typical of today's cost-manufactured shit.

Also, a fuse may not help. It takes time for a fuse to blow - even for a fast-blow type. In some cases, that alone may not be enough to prevent damage to the GPU and its RAM. A good VRM will ramp up T_on time on its bottom-side MOSFET and ideally indefinitely leave it turned ON when it starts detecting over-voltage on the output. But seems that not all VRMs know how to respond well (or quick enough) to an over-voltage / high-side MOSFET failure.

I've had this happen on an Intel motherboard whose upper MOSFET shorted multiple times on me while trying to repair its VRM (issue turned out to be a partially-dud PWM driver.) I had to replace the same upper MOSFET no less than 4 times. And not once did it damage my CPU. Each time the upper MOSFET shorted, the lower one closed and made the over-load / short-circuit protection on the PSU kick in, thus completely shutting everything down. Of course, I was using a modest PSU with low 12V current rating, so it shut down quick. I -don't- like high-power single 12V rail PSU that can do more than 30 Amps without any sort of limit. I honestly consider these a bit of a fire hazard, especially anything over 700-800 Watts, because even with an 8-pin and 6-pin PCI-E power connectors, that can still push upwards of 60 Amps through those 6-8x 18-16 AWG wires... or about 8-10 Amps per wire - and that's without the PSU even thinking it's overloaded.

So if you want to stay on the safe side when testing hardware, use a PSU that has several separate 12V rails with 18-22 Amps limit. This is by far the quickest way to prevent damage to video card, motherboard, and even PSU wires.

Last edited by momaka; 06-01-2021 at 07:47 PM..
momaka is offline   Reply With Quote