Broken GTX 980M

Discussion in 'Hardware Components and Aftermarket Upgrades' started by Darker01, Nov 11, 2017.

  1. woodzstack

    woodzstack Alezka Computers , Official Clevo reseller.

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    Well the mosfets are easy enough to replace, any electrical engineer should be able to do that for you.
     
  2. Khenglish

    Khenglish Notebook Evangelist

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    7 ohms is definitely bad. The only way to find a short is to pull FETs one at a time until the short disappears. There are only 3 FETs for the core so there are not many to try.

    7 is odd though. I would expect a blown FET to be 0. Measure the resistance across the big rows of caps. There is a row of 6 and a row of 2. They are black. The row of 6 is the core and any non-zero resistance is fine, even like .5 ohm. The row of 2 is the memory. Memory is usually between 10 and 50 ohms.
     
    Last edited: Nov 13, 2017
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  3. Darker01

    Darker01 Notebook Enthusiast

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    I measured some 12 Ohms +/- 5% resistors and an 8 Ohm 20W power resistor to confirm that my multimeter is accurate enough at low resistances. Got ~13.5 Ohm and 9.5 Ohm, respectively, so I reckoned I'm off by at least 1 Ohm.

    I measured the resistances in the caps that you mentioned again, and I got another set of values this time. I thought they were MOSFET by mistake. The row of 6 all measured around ~9.5 Ohms, and I noticed the resistance measured across the power input pins is also the same (temperature effect? late evening vs. 6:00 AM?). Row of 2 measured at around 24.0 Ohms.

    I edited my previous post to indicate a mistake with the memory cap resistances.
     
  4. Khenglish

    Khenglish Notebook Evangelist

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    Interesting. It sounds like the core voltage may have gotten shorted to the supply voltage. On the row of 6 the bottom side is the core voltage, and on the mxm power tab the right side is power. Check the resistances between these. It should be in the thousands but it sounds like you'll read 0.

    Other than the GPU core's power FETs there are only 2 components with connections between the GPU core voltage and the card's supply supply voltage. They are the VRM, and the phase driver for the GPU core's 3rd power phase. Both of these chips are on the backside near the top of the card, and the VRM is the bigger of the two. I've never seen these chips fail and short the GPU voltage and supply voltage together, but it's possible. If your VRM died I expect the GPU core to be fried. A working VRM can protect the core from overvoltage if a FET of the phase driver died, but if the short is in the VRM there's nothing to detect it.

    I'd still first pull and check each power FET for the GPU core. They're the 3 big chips at the very top of the card.
     
    Last edited: Nov 13, 2017
  5. Darker01

    Darker01 Notebook Enthusiast

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    Thank you. I'll check the resistances after I get home.
     
  6. Khenglish

    Khenglish Notebook Evangelist

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    Here are images showing what's what assuming that you do read 0.


    [​IMG]

    The core power FETs are boxed in red. One of them is probably dead.

    [​IMG]

    If it's not a dead power FET, then it's either the VRM or the 3rd phase's driver (phases 1 and 2 are integrated with the VRM).
     
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  7. Darker01

    Darker01 Notebook Enthusiast

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    Long day. Just got home. Checked the resistances between the power tab and the capacitors' end with the band and got essentially 0.
    I'll start looking for the replacement power FET later this evening.
    I'm curious. Did I just so happen to have a bad 980M, or are the more recent clevo cards bound to fail like mine eventually?
     
  8. Darker01

    Darker01 Notebook Enthusiast

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    The power FET has 87350D written on it. Found the product page from TI (link). I still have my university email, so I requested 5 samples from them free of charge. I think they'll arrive in a couple of days.
    In the mean time I guess I'll start ordering equipments to desolder those FETs.
     
  9. Khenglish

    Khenglish Notebook Evangelist

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    You just need a hot air gun, solder flux, and a heat gun for it.

    Remember that 2 of the FETs are still good, so just pull one at a time and check the card if it is ok. I recommend filling all 6 FET pads. For just getting the card working though the unused FET pad already has all the required solder and is easier to solder a FET onto than reusing the original pad. Just remember to follow the pin 1 arrows so you don't put the FET on backwards.
     
  10. Darker01

    Darker01 Notebook Enthusiast

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    Thank you for the equipment advice. By hot air gun and heat gun, I assume you are talking about those hot air rework station and the hand held extremely hot air dryer thing?
    Not sure how it go with other components, but do you think if I get away with just using the hot air gun to remove the FET directly with sufficient heating of the surrounding area?

    With regard to the part selection, I think I'm going for this by the virtue of the reviews + EEVBlog video of a similar device. Hopefully it'll work well enough such that I won't have to return it.
     
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