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Someone who can inspect/reflow a GPU

Discussion in 'Electronics & Electrics' started by sammy_b0i, May 3, 2020.

  1. merlin13

    merlin13 Member

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    Weeeeell, putting aside lead free is supposed to be "stronger" and more resistant to board flex breaking the junction when done properly (and the higher eutectic point), Yes and No.

    Problem with ditching the lead free is heating the chip to get it off the board without lifting that last recalcitrant pad, cleaning the solder off the board and the underside of the chip, applying juuuuuust the right ammount of leaded paste to each and every pad whilst making damned sure it doesn't bridge across to an adjacent pin when you drop the chip back on it, re-aligning the chip to within a poofteenth of the right position and keeping it there whilst you heat it back up again.

    And you have to hit the device with lead-free soldering temps anyway to get the damned thing off in the first place - far friendlier to only cook the suspect thing once.

    If you've got access to a serious rework setup then yeah, worth the effort. Especially if you're being paid to do it as a career as well... ;)

    Far easier to flood the underside of the BGA with good liquid No Clean flux then hit it with hot air or IR. And hope the bits on the underside of the board don't fall off either if you get too keen with the hot air...

    And I've got three 32- and 42-inch LCD/LED TVs here right now that I can show you that responded reliably to that second technique, plus a handful of other devices over time that even using my Yum Cha hot air station all behaved well afterwards to that method.
     
    Last edited: May 5, 2020
  2. GrandmasBoi

    GrandmasBoi Member

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    Yeah what you say is true, however I think everybody can relate to this story.. When I was young dumb and full of cum I used to reflow my xbox 360 rrod, first reflow fixed for 2-3 months second reflow 1 month 3rd 2 weeks and so on, so reflow won't "fix it" just breathe a few weeks time into it. Pretty much leaded solder was banned around mid 2000s in commercial electronics so they don't use non leaded because its better, its actually much worse, get cracks cold joints etc alot more.

    To fix it properly you need to reball it with leaded. Yes the pads need to be cleaned using wick and hot air, and need a stencil to apply leaded paste to the chip pads. Aligning is not that much of a issue with leaded solder as it will self align once solder melts, some claim even 40% error margin (only leaded solder self aligns)

    Yes for a big chip you need a ir workstation to pull off the chip and see heat distribution. Sure some heros on YT do it by hand but its no way to do it.

    I reballed many smd chips but on mobile phones by normal air station and above mentioned steps but a full size smd chip is too big.

    Only saying this not to get OP hopes up, flux and a heatgun is one step above using a Hairdryer for 10 mins on it
     
  3. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    Well, the bad news is these photos are post a few rounds of isopropyl spray and scrubbing with a soft toothbrush to really get in between the chips. It was far muckier before. The sticky, kind of... grease substance was in between smaller components, and still is.

    The previous owner had replaced one of the fans at one stage also. I'd assume with the suspicion that it's an ex-mining card would ring true. I looked at the back cluster and felt it looked "darker" than I'm used to seeing, but if that's due to excessive heat, then this isn't sounding like a great expedition from the get go.

    In working condition it's worth ~$600-750 used at the moment, and I paid substantially less than that. And when it posts, it handles things quite well. As mentioned, I left it looping Unigine Valley for ~18 hrs and it didn't break a sweat. I've only invested ~$20 for some new pads and paste, and then my time, which is mostly worthless (!). What do you think?
     
  4. grrrr

    grrrr Member

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    I recon one of the Magic R22 chips has been leaking smoke... :leet:
     
  5. /invariance\

    /invariance\ Member

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    If it doesn’t artifact when it does run, consign the card to its own box, keep booting until it is recognised and leave it folding@home until it totally dies. :thumbup:;)
     
  6. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    So things just went from not that great, to not good at all.

    Got a really soft plastic flexible little pick to clean between those sticky SMDs and one immediately popped off as soon as and sidewards pressure occurred from scraping out the gunk between the chips.

    https://imgur.com/a/oPFhf5E

    :(
     
  7. GrandmasBoi

    GrandmasBoi Member

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    At least the pads are there still, with the right tools and some experience pretty easy to re-attach but not doable with a bigw solder iron

    No idea what that residue is, left over flux from somebody reflowing the card or something spilled?

    The focus on the pictures is not really great, maybe try holding the camera further away and zoom in more rather then holding it too close, but could be just how your camera is
     
    Last edited: May 5, 2020
  8. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    Not sure, the tiny parts I've gotten off so far has the texture of grease, kind of. Reddish in colour. I've got pretty average soldering iron but the tip is pretty small.. it is just a case of holding it in place and dabbing the pads until they take hold, or something else?
     
  9. GrandmasBoi

    GrandmasBoi Member

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    What you will need to do is clean the pads, add flux, mix in some new solder. Wick it down and add new solder again (optional) the more u mix and clean the more new solder you leave on the pads meaning it will bond better.

    Once your pads are ready flux it, the smd chip will stick a bit to the flux so position it as best on the pads as you can.

    It helps now to hold the smd with tweezers if u have a steady hand. Have some solder on your iron tip and go over the smd edges and the pad edges. It will melt and bond the smd to the pad.

    If u got a real shaky hand holding the smd down with tweezers it might do more harm then good.

    You can also use hot air if you got a heatgun?
     
  10. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    May be out of my skillset, but I'll inspect the irons I've got available and see how small the tip gets. Watched a video involving getting one side of the pads with some solder on it, then placing the SMD in place, touching the pad to re-melt the solder, and the SMD should stick in place, making it easier to do the other side. They may have been the larger ones in the photos though.
     
  11. GrandmasBoi

    GrandmasBoi Member

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    Yeah get out your tips and see if they fit in where you working, otherwise for pads which you can't access clean, flux solder the pads, flux again place smd down then bring down ~360 air with a low airflow, few seconds and you will see the smd wiggle and bond to the pads.

    Ps your pads have enough room to do it with a fine solder tip
     
  12. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    I don't see any tips fine enough... zzzzzzz. Not sure what to do with it now.
     
  13. GrandmasBoi

    GrandmasBoi Member

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    If you haven't already put the smd in a zip lock bag or a safe place, then look around oc for anybody near you that can solder
     
  14. merlin13

    merlin13 Member

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    Greasy stuff that Isopro doesn't shift??

    Sounds more than a little odd - that has to start to drop in the realm of Severely Silly Shit, and leans towards Stupid Shit - as in either glue or possibly epoxy.

    Wonder if the previous owner was that clueless to actually glue that part on? Knowing a few Bitminers wouldn't put it past him/her/it....


    Aaaaanyway, so now go for broke and carefully hit it with acetone, knowing that'll lift the component designations and the solder resist if One Gets Too Keen.

    Do Not Use A Plastic Brush - acquire a natural-bristled 1/4" or smaller paint brush and trim the bristles right down to about 5 or 10 mm from the holding pommel. Make them stiff but still a tad flexible.


    As far as resolderering, either someone nearby, or bag it all up and haggle someone at the end of the postal trail to Do The Deed.

    Obviously would be far handier to get someone local rather than Post, Solder, Return Post, Suck It And See, then ponder any GPU rework thereafter - else just Go For Broke and hit all of it.

    Got a TV repair shop in the district perchance?...


    And some more thoughts.

    Without pulling the other two off the board to put onto the right type of meter I'd take a punt and hazard those three parallel bits are capacitors, as those three in parallel with the large pads at each end lean towards a Tantalum cap option.

    But on saying that, the orientation of the three LB519, -520 and 521 designations lean towards inductors - anyone?

    Either way, the other two need to come off the board and all three Unknowns poked with the right type of meter, to see what they buzz out as and whether they're still functional.

    Got a TV repair shop in the district perchance?... :)


    Other curiousity - regardless what they actually are, intrigued that the board could be that twitchy/"finely tuned" that its actually that unreliable if one of them simply fell off.

    All assuming the unreliablity there IS actually related to those of course...
     
  15. _zak

    _zak Member

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    LB is a common designation for ferrite beads, used for filtering power lines (like the clip-on things you can get for cables). The gunk around there is almost suggestive of flux, but if it's not moving with isopropyl that's unusual. It almost looks like some kind of corrosion, supported by the fact that one of the components came off with indirect force, but that unless the past owner attempted reflow with (acidic) plumbing flux, that's not likely. You can see more of it around Q535 to the left in the last photo of your first set.

    Whatever happens next, cleaning will be important. If isopropyl isn't shifting it, you could try hot soapy water followed by distilled water and then isopropyl (if it weren't for the parts falling off, the dishwasher (yes, really!) would be a good option).

    Beyond this, I'm afraid it's much the same as others have said. There's clearly been some heat stress to the card, and repair is going to be tricky without specialist equipment. Even if you do get cleaned up and parts back on, it's impossible to fix damage that may have occurred to internal traces and/or the silicon itself. On the flip side, that gives you nothing to lose if you do attempt repair, with a big potential upside. Good luck!
     
  16. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    Having had a look, I'm really not skilled enough to get that thing back on. Hands aren't steady enough, and don't have the equipment.

    Considering putting it up and seeing if I can get back what I paid for it. There's a few places around Canberra that are "TV Repairs" but not sure how to separate the wheat from the chaff in terms of an "order & replace a replaceable power supply" person, and a "test an SMD and replace if necessary, ultrasonic clean and reflow board"... person.
     
  17. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    I could reassemble it, and see if it still boots with a few power cycles, too.
     
  18. elvis

    elvis Old school old fool

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    CRT TVs by any chance?
     
  19. GrandmasBoi

    GrandmasBoi Member

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    That smd that fell of is most likely a filter, everything else around is labelled e.g R284 = resistor C496=Capacitor D395=Diode

    This one is not labelled it looks like a cap or a filter. U can put your multimeter in diode mode and test those caps including the one that fell off. If they all show continuity they are filters (unless they are caps and line is shorted)

    Anyway this is only mudding the water, I doubt that smd has anything to do with your problem, its easy to knock components off people do it all the time with screw drivers.

    Obviosuly this card had a hard life and usually the components that wear the most from prolonged heat are the gpu/cpu main chip. Most common is board bending/bga joints under the chip losing connection. A reflow will fix this in short term but in long term it will happen again unless you reball.

    Are we positive its bga joints? - NO
    Is it likely - YES
    Do we know the history of the card and what the sticky residue is - NO
    Did we do a good physical inspection under a microscope or very good high res? - NO

    So basically your taking pot shots here, its a bit of a needle in a hay stack. As a hobby I spent hours split over days weeks diagnosing motherboards, changing components, reflowing etc until you get to the problem (brute force)

    If you going to be paying somebody ph forget it.

    Its easy to get derailed and follow totally useless paths e.g you knocked off a random smd which looks sus now you need to measure/investigate/reattach and its prob nothing to do with your problem.

    Once I removed a motherboard chipset and ordered a new one soldered it in (my hunch was very strong) but the problem was something else
     
  20. OP
    OP
    sammy_b0i

    sammy_b0i Laugh it up, fuzzball!

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    Got any spare time on your hands, and don't want to be paid hourly? :lol:
     

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