2 toasty GF6800s

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  • Scenic
    o.O
    • Sep 2007
    • 2642
    • Germany
    #1

    2 toasty GF6800s

    i don't really now where i should put this thread, so i just put it here..


    i now have 2 dead GF6800 AGP cards lying around here...

    one of them came from a complete system i got for free as defective, the other one died in my stepfather's PC...

    symptoms are the same..

    complete short on the 12V rail of the additional power plug.

    the one that died in my stepfathers PC is a GF6800 (without any letters).
    it started blacking out some day while surfing on the net...
    screen turned black and "no signal" message..
    sometimes it worked after power cycling, sometimes it stayed dead until we gave it a little bit of time to cool down (like 10mins or so..)

    then some day, the same thing happened, but the PC turned off completely and you couldn't turn it on again.. (short circuit protection of the PSU kicked in..)

    after being puzzled for a while it turned out that the sys turned on again if that extra power plug of the graphics card wasn't plugged in.
    gave out no picture though..

    we found that out by accident.. (just forgot the plug while trying around)

    testing with my DMM, the 12V rail on that card is completely shorted.

    the second card.. .well.. i got it in a dead complete system for a few bucks...

    that guy thought the board and/or the PSU were dead (you couldn't turn it on at all)...

    turned out to be the exact same problem. 12V of the additional molex plug shorted... (the rest of the sys worked perfectly fine with a different graphics card.. *yay*)

    i think both cards died the same way.. seems like it..

    on that "complete sys card", there are some obviously burned out components, but my knowledge about this stuff is very limited... (i'm that cap/recap kinda guy, not the general electronics freak..)

    so... any ideas what those components are (those 2 identical ones are mosfets i think) and how to fix this...?

    in that 1 second the pc tries to turn on, the left most component gets so hot that the flux starts to bubble (within 1(!)sec. ) but in general, the whole area seems to get quite hot there (discolored PCB)..

    this is the 2nd card (the complete system one)...
    can't find the other one at the moment...
    leftmost:
    2168
    4F1

    the other 2 (identical):
    IOR (?) 352H
    H74U
    F7832





    location..



    i'd like to fix those as they're too good cards to throw away (at least when they're working ) and this seems to be a common problem for the GF6800xx cards (lots of dead ones with the same symptoms on ebay for example)

    any ideas?
    especially that 2168 4F1 thing worries me.. couldn't find anything useful on google..
    Tags: None
    • Per Hansson
      Super Moderator
      • Jul 2005
      • 5895
      • Sweden
      #2
      Re: 2 toasty GF6800s

      Those are most likely power mosfets, I've replaced them on my previous 7900GT after I managed to mishandle it... Working great still

      The problem is that under normal operation those mosfets get over 100°C hot, they need both heatsinks and active airflow

      This thread might be of help; http://www.xtremesystems.org/Forums/....php?p=2521669
      "The one who says it cannot be done should never interrupt the one who is doing it."

        Comment

        • Scenic
          o.O
          • Sep 2007
          • 2642
          • Germany
          #3
          Re: 2 toasty GF6800s

          i just played around with my DMM..

          those 2 HEXFET Power MOSFETs by international rectifier seem to be OK...

          however.. the other thing (still can't really identify it) is completely shorted.
          all pins = 0 ohm

          and things got really quite hot there...

          some small SMD caps (edit: surface mount lytics.. 16V 100uF) on the other side of the PCB are shorted, too..
          probably got cooked on the long run..


          hmm.... possibly this thing...?
          -> http://www.alldatasheet.com/datashee.../HAT2168H.html

          anyways.. thx for your post :]
          i didn't expect someone to post on the same day...

            Comment

            • Scenic
              o.O
              • Sep 2007
              • 2642
              • Germany
              #4
              Re: 2 toasty GF6800s

              okay... as i had nothing to lose (card was dead anyway) i desoldered that unknown 2168 thing which turned out to be a HAT2168H Silicon N Channel Power MOSFET and did the same thing with a STM4884 i found on a dead old (skt.370) laptop mainboard which happens to have 4 of them on it...

              soldered it onto the GF6800.. put the heatsink/fan stuff back on it.. popped it into my test system (P4 1,8GHz Northwood) and viola...

              POSTed and booted into windows :]

              kept an eye on the temp of those mosfets though..

              seems to be okay so far... it's working in 2D...

              can't test 3D though, because the PSU is a bit too weak (250W FSP) for 3D testing a GF6800 IMHO..

                Comment

                • Per Hansson
                  Super Moderator
                  • Jul 2005
                  • 5895
                  • Sweden
                  #5
                  Re: 2 toasty GF6800s

                  If the PSU has the 12v rails for P4 spec then it'll be fine
                  Anyways, congratz on the fix!
                  "The one who says it cannot be done should never interrupt the one who is doing it."

                    Comment

                    • Scenic
                      o.O
                      • Sep 2007
                      • 2642
                      • Germany
                      #6
                      Re: 2 toasty GF6800s

                      ...and the second card (GF6800 without letters) works fine aswell

                      happens to have the exact same layout with the same failed power mosfet

                      replaced it with another one off the dead notebook board and it seems to work fine too :]

                      so i revived a 6800LE and a 6800

                      now i only need to check the temps in 3D...

                      i guess i'm gonna put some semi-smallish heatsinks on those 3 power mosfets (per card) with thermal glue..

                        Comment

                        • Per Hansson
                          Super Moderator
                          • Jul 2005
                          • 5895
                          • Sweden
                          #7
                          Re: 2 toasty GF6800s

                          Yea, heatsinks are good, monitor the temps first to make sure it's needed of course
                          But something tells me that's the reason yours failed...
                          Arctic Silver Thermal Adhesive is nice (unless you want to remove the heatsink afterwards as you saw in that thread I linked LOL )
                          "The one who says it cannot be done should never interrupt the one who is doing it."

                            Comment

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