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Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

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    Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

    Hello! This is my first thread here. This is the first time I try to repair a shorted GPU, but I'm afraid that I'm short of knowledge to be able to isolate the problem. I would like to check if it can be saved, or it's too difficult/expensive and it's not worth to it (but I would love it!) I tell you...

    I've got this shorted graphic card:




    I see no evidence of damaged components, so let's see what happens with tests.

    I detected a short in the 8-pin plug: without it plugged and the rest on, the motherboard run; with it plugged, usual short behaviour in the power supply.

    So, I looked for the 8-pin scheme and found two:




    One says that pins 4 and 6 are "sense" (I understand that they are connected to sensors or something for detecting or determine the current input), so I'm not sure about what their behavior should be; buuut found with the classic "beep" function with my multimeter that there is a short between pins 8 and 3, and 8 and 2. So I guess that some component is damaged, "bridging" or something. Of course, I haven't found any scheme of this GPU in the net (would be too easy, I guess!)

    So, I've several doubts by the moment:
    1. For those who had already experience with shorted GPUs, which component (or components) do you think is more probable that is faulty?
    2. What are the "sense" pins exactly?
    3. What do you suggest for my next step?
    4. By the way, I've read about some cap meters that works with them within the circuit. Do they worth it really? I was thinking about getting one, just to avoid unsolding all the caps each time.


    Cheers!
    Attached Files

    #2
    Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

    For those who had already experience with shorted GPUs, which component (or components) do you think is more probable that is faulty?
    VRM mosfets

    What are the "sense" pins exactly?
    It's intended to read the voltage at the end of the cable, in most power supplies this wire isn't present

    What do you suggest for my next step?
    Check for shorted mosfets, but remember, low side mosfets will show almost like a short (unles you can disconnect the output)

    By the way, I've read about some cap meters that works with them within the circuit. Do they worth it really? I was thinking about getting one, just to avoid unsolding all the caps each time.
    It depends of the circuit design, if you have components in parallel, you'll have to desolder the capacitor
    Last edited by cpt.charlie; 02-06-2017, 04:09 PM.

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      #3
      Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

      Thanks, Charlie!

      There are two types of MOFSET here in the VRM: 4935N and 4921N. Testet in the circuit with the source and gate pins: all 4935 seem to be good to me (reducing impedance, I guess that's a normal behavior). About 4921, there's one (I mark it in this photo) that has very low impedance (about 8 ohms if I'm not wrong, it beeps). The other 4921 ones shows higher impedance.



      I don't know if it's a low-side one (I tried to figure it out, but I don't know how checking the datasheets), but that's the only one with that behavior. Maybe should I try unsolded?

      What do you think? Did I make the test right (with S and G pins), or should I do something different?
      Attached Files

      Comment


        #4
        Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

        You have to check source to drain not gate to source, if you need to know if it's a low lode mosfet, low side mosfets usually go by pairs and source is connected to GND, on high side mosfets drain is connected to VCC and usually it's one per phase.

        Comment


          #5
          Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

          In that case (source to drain), beeps in 16 of 18 mosfets (the ones next to R125 inductors, marked in the photo). About 1 ohm, maybe 2.



          What could it be? Is it for sure that they are faulty, or maybe the short is before them?
          Attached Files

          Comment


            #6
            Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

            Low side mosfets will beep because the GPU is connected..... if you measure from 12V connector to GND, is it shorted?

            Comment


              #7
              Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

              Charlie is right probably is just a MOSFET, the high side tend to die first so probably the problem is over there, I would check just to be sure the fets on the memory vrm, and as a suggestion a delid for those GPUs help a lot with temps because Nvidia used cheap thermal paste on hose really hot running cards instead of solder or some polisyntetic paste, only do this if you are Shure and heat up the GPU a bit before to soften the glue that hold the IHS so it will be easier to stick the razor under it

              Comment


                #8
                Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                Charlie, sorry for my ignorance, but I'm not sure about what you mean. 12V = VCC? There's short between 2 and 8 and 3 and 8, for example, in the 8-pin connector. If 12V = source pin in mosfets, they are connected to ground all 18 (and VCC as well).

                Hi-side mosfet are always before low-side, or it could be in the other way?

                Drack, what do you mean with memory VRM? What part is memory? (I understand that you don't mean the GDDR5 modules)

                Comment


                  #9
                  Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                  Yes, VCC = 12V in this case, and high side mosfets are always before low side mosfets look at the image as reference.
                  Attached Files

                  Comment


                    #10
                    Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                    The ones with the inductor that says eR33 those are the ones for the ram and I think this card does not have an auxiliary rail, those where added later on their newer cards, btw is that the photo of your card? Because it doesn't have caps after the GPU vrm
                    Last edited by Drack; 02-09-2017, 05:19 PM.

                    Comment


                      #11
                      Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                      Great, thanks!

                      That's right, Drack; the photo is the actual graphic card. It hasn't caps after the GPU VRM (maybe the ultra-little things with a cream color are caps, but I don't think they can manage the current for that "little" GPU ). I thought the same after looking at other graphic cards photos on the Internet.

                      So, also checked the mosfets in memory VRM and there is no short between source and drain in any of the four of them. They're 4935N and 4921N as well.

                      So, my next questions are:
                      1. Do I have have to unsold mosfets (high-side ones first, if fail, then low-side ones) to check if someone is really faulty, or do you suggest another test before? If unsoldering, do you think there is a preferred order to do it?
                      2. Drack, when you said that you recommend with temps, do you mean that you recommend that, if I replace mosfets, I do it with ones with thermal pads like the ones in the scheme that uploaded Charlie? If so, do you recommend some model in special?

                      Comment


                        #12
                        Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                        I don't recommend delid per se, because it's kind of dangerous if you push the razor too much and chip the die or cut some traces on the PCB, but is worth it if you want lower temps even 15c on some cases, for MOSFETs cooling this http://m.ebay.com/itm/Lot-8-pcs-New-...257Ciid%253A11 should work, they are for ram but work perfectly for vrm sometimes you have to cut them a bit to fit but is Copper so it will be easy. If you want to check the MOSFETs that's the best way, I have done that with a heat gun but on a dead board just for practice, never changed one of those, but everything indicates is a MOSFET failure so give it a try, check YouTube videos if you don't know how to do it and try on an old dead Mobo o gfx.
                        Drack.

                        Edit: http://m.ebay.com/itm/New-8pcs-Coppe....c100408.m2460 this are cheaper and look like they would fit, only a bit of cutting on the find and you should be ready to go.
                        Btw if you want to put caps a 820uf solid caps is what you normally see on those or 470uf tantalums
                        Last edited by Drack; 02-11-2017, 11:28 AM.

                        Comment


                          #13
                          Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                          Remember, a capacitor could be the culprit too, if you have a lab power supply you can inject some controlled current into the 12v line and search for overheating components, use some alcohol and try to detect a spot that evaporates much faster than the rest.

                          Comment


                            #14
                            Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                            Liquid flux could work too, just try it with low current, in a schematic you could check what is connected to those pins and test those

                            Comment


                              #15
                              Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                              Oh, right, Drack! Didn't know you were referring to heatsinks. I didn't take photos of the two heatsinks that this GPU has, but one of them touches the mosfets (you can see that heatsink in the photo, the dark part corresponds to them). Anyway, I'm not sure about the efficiency of that dark thing, maybe I'll add some thermal paste to the mosfets too when it's fixed.



                              Thank you very much to both! I have a painting heat gun, I think it will be enough. But maybe I'll be brave enough to try what Charlie said (I have a lab power supply indeed)... I'll decide after googleing enough. These (new for me) testings will take me a while this week, but I hope to come back with news before the week ends.

                              Happy week!
                              Attached Files

                              Comment


                                #16
                                Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                                Well don't put thermal paste on the MOSFETs, thermal pads for MOSFETs, and I was talking about deliding the GPU but forget that part if you don't have heat troubles, that dark thing will do the job, you could try with one of those heat guns, but be careful and watch some tutorials please.
                                Good luck!

                                Comment


                                  #17
                                  Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                                  It weird that we both speak Spanish but have to talk on English because of the forum
                                  Last edited by Drack; 02-18-2017, 07:31 PM.

                                  Comment


                                    #18
                                    Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                                    That was that I thought, Drack; but including Charlie (I guess he's Spanish as well)

                                    I made a little research of desoldering with heat gun in Youtube and finally desolder MOSFETs with this one:



                                    First, I tried with two death motherboards (one per MB), and although the first one I guess I kill it (ups! open circuit between all pins or full short), the second one seems to be good. But when I tried it with the graphic card (with three layers of foil around to protect the rest of components), I had heated it (exposing the MOSFET with a circle move a few seconds, removing the heat gun, try to move, and repeat) more time that the other ones, and I couldn't move it! So I preferred to stop before and ask you:

                                    - Do you think it's ok that I keep more time heating it until it moves? I set the heat gun to maximum (2000W and almost sure I killed the first one already with it) and used a curved tweezer to move it like this one:



                                    Or maybe I should try something new? It's ok if I have to wait, I don't want to kill the GPU that fast I'm waiting for a flux coming (bought online), maybe it will be easier if I make the MOSFET to have a little flux bath before trying again?
                                    Attached Files

                                    Comment


                                      #19
                                      Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                                      Well flux may help with the solder staying where it should, but I think 2000w it's too much, the ones I desoldered were done with a 500w heat gun, it worked alright all the 15 MOSFETs are OK, the tweezer is OK, they should work perfectly, send a message to momaka, he have done this before a lot of time maybe he can help you

                                      Comment


                                        #20
                                        Re: Shorted Graphic Card Gigabyte GV-N580UD-15I Rev 1.0 (nVidia GTX 580)

                                        just a gentle reminder. make sure u use the right type of flux. the flux has to be either (R) non-activated flux or (RMA) mildly activated flux. do NOT use (RA) activated flux or plumber's flux, welding flux or some such. those are corrosive and will melt the pcb. that is all...
                                        Last edited by ChaosLegionnaire; 02-19-2017, 09:52 PM.

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