Does this GPU from my iMac look normal?

Discussion in 'Mac Basics and Help' started by The.316, Jul 30, 2019.

  1. The.316 macrumors 65816

    The.316

    Joined:
    Jul 14, 2010
    Location:
    25100 GR
    #1
    I have been running unsupported Mojave on my late 09 27” iMac. It was working fine for a while, until it restarted, and I started getting this:

    6B75AE87-5F50-410D-A284-F031043183C2.jpeg
    B2638A72-B292-46C6-A76F-9FF28EE71796.jpeg


    Someone told me that it’s probably a bad graphics card. I removed the card, and this is what it looks like:

    A55240BE-3AE9-46A3-929D-110FEC89CD57.jpeg A713EC2E-7F84-4551-A268-751EFF75C29F.jpeg 54F42579-174C-40F0-9013-CB9F3C9B5D67.jpeg EFEEEC67-5B90-42DF-B848-3FE144C12053.jpeg 82D4F925-2ECF-4200-A6AF-04B39F25C4A2.jpeg C8025789-7CE5-4334-ADF2-0C1D9B0E5849.jpeg

    There seems to be some discoloration in some areas, probably from high levels of heat. Would cleaning both the card and heat shield do anything? I thought maybe if I added new paste and thermal pads would do something. Or should I just look around for a replacement card?
     
  2. velocityg4 macrumors 601

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #2
    You can always try cleaning. It probably won't help much. You could get lucky. Also try booting into recovery mode from an officially supported version of macOS and do the usual SMC, PRAM and NVRAM resets.

    If everything fails bake it. Sometimes that revives a dead GPU or motherboard. Temperature and time are critical. You also can't budge it until it cools down. Via a slow cool down.

    This is a last ditch effort. When all else has failed. You try this since there is nothing left to lose when you have determined the part is dead. I've revived several devices this way. This isn't considered safe for the parts. It can destroy them. That's why it is a last ditch effort. They are dead anyways so why not try it.

    Unlike the guide I go straight to 385F (195C) for 13minutes. I'd rather minimize the number of trips a part takes through the oven. The repairs at the higher temperature have held up well. This repair could only last a few hours, days, weeks, months or years. I've had good luck so far. Lasting one to two years. Perhaps it's because I go with a more aggressive heating pass the first run.
    https://www.ifixit.com/Guide/Tempor...raphics+Card+by+Heating+it+up+in+an+oven/2240

    I couldn't find the original guide I used the linked one is close. I'll list the steps I take which may vary a little. I've revived two Macbook Pro's, two GPU and a Dell Laptop this way. Each one I determined as a candidate because of similar GPU issues.
    1. Clean thoroughly with rubbing alcohol
    2. Remove any plastic you can. Remove any glue, stickers, labels, film, &c.
    3. Create a flat aluminum foil tray to place under card (I put his all on a cookie sheet to aid in moving the card quickly into the oven)
    4. Crumple up four aluminum balls to put under card
    5. Create an aluminum hood to go around any plastic components to minimize melting
    6. Preheat oven to 385F (195C)
    7. Ventilate room as well as you can. Open windows. If you have an home exhaust fan or range hood which exhausts (some just carbon filter). Turn it on.
    8. Quickly place card in oven and close door (you want to minimize heat loss)
    9. Bake for 13 minutes
    10. Turn off oven and crack door open to slowly cool. Allow to cool without moving for twenty to thirty minutes.
    You're going to need new thermal pads and thermal paste when you reassemble it. I don't know what thickness pads it uses for the VRAM or if it is flush fit of thermal paste all around.
     
  3. jabbawok macrumors 6502

    jabbawok

    Joined:
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    Location:
    Worcestershire
    #3
    I've had luck sticking mine in the oven, but that's usually when they don't work at all, because the GPU has lifted off the PCB a bit and the solder balls have become detached. I'd look for a replacement if I were you. I doubt they cost much from an older model.
     
  4. The.316 thread starter macrumors 65816

    The.316

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    #4
    I’m going to try baking it. I have to wait a few days because I ordered some thermal paste. I’ll keep you guys updated. Thanks for the responses.
     
  5. jtara macrumors 68000

    Joined:
    Mar 23, 2009
    #5
    Those chips had WAY too much thermal paste on them! It looks like somebody applied it with a trowel. (Is that thermal paste, or is that spackle?! Honestly, it looks more like spackle or toothpaste than any thermal paste I've ever seen...)

    Is that the original thermal paste? Had it been replaced? Did you buy the card used?

    The purpose of thermal paste is to fill small gaps and irregularities. The paste itself should not CREATE a gap between the chip surface and the heat sink! A good way to insure that is to use a credit card or similar to wipe off the excess.

    The thermal conductivity of thermal paste is WAY LESS that that of the chip package or the heat sink. But it is also WAY MORE than air. Thermal paste is meant to fill AIR GAPS and thus provide SOME thermal conductivity in places where the heat sink doesn't have contact with the surface of the chip package. It shouldn't prevent the heat sinks from contacting the chip packages. That completely defeats the purpose of the thermal paste.
     
  6. velocityg4, Jul 30, 2019
    Last edited: Jul 30, 2019

    velocityg4 macrumors 601

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #6
    What thermal paste did you order?

    Heatsinks usually have a gap on VRAM. Normally they use thermal pads on stuff like VRAM. Since they don't generate as much heat as a GPU or CPU a couple watts vs a few dozen to a couple hundred watts. So they don't need as much. Larger GPU frequently just rely on airflow over open VRAM. They likely just used a thick paste instead of pads.

    This also leads to a difficulty for the Op. There may be a gap too wide for GPU/CPU paste to fill.
     
  7. The.316 thread starter macrumors 65816

    The.316

    Joined:
    Jul 14, 2010
    Location:
    25100 GR
    #7
    Just some paste from where I work. Does it have to be specific?

    http://www.sun.gr/index.php?SCREEN=products_detail&ProductID=243216


    Do you have any suggestions? Can I use the paste on all the required components of the card, or do I have to use pads as well?
    --- Post Merged, Jul 30, 2019 ---
    I figured it was too much as soon as I saw it. It looks like toothpaste, and it has the feel of dried out toothpaste. That is actually how it came from Apple. Too bad I couldnt contact them regarding how bad of a job they did.
     
  8. velocityg4 macrumors 601

    velocityg4

    Joined:
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    Location:
    Georgia
    #8
    That should be decent enough. Likely better than whatever Apple used.

    Thermal Grizzy Kryonaut would be the best non-conductive paste. But you aren't overclocking the GPU and a thin application of any decent thermal paste should perform better than factory thermal paste. Since they slather it on.

    Since the bottom of the heatsink is copper. You wouldn't want to use something like Thermal Grizzly Conductonaut due to the reactivity with copper. Plus it takes a lot of care to avoid a short circuit with liquid metal.
     
  9. The.316 thread starter macrumors 65816

    The.316

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    #9
    And thermal pads? Just generic ones will suffice?
     
  10. velocityg4 macrumors 601

    velocityg4

    Joined:
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    #10
    I don't know what thickness you need. 0.5m, 1.0mm, 1.5mm and 2mm seem to be standard. You can see what thickness those white flakes are. As the pads compress a little. You don't want them too thick as you won't get a good seat on the GPU. Too thin and they are useless.

    Arctic pads are the minimum I'd get. Thermal Grizzly Minus Pad 8 is better. Fujipoly Extreme X-e looks really good. Alphacool Eisschicht and Fujipoly Ultra Extreme XR-m look to be the best for thicker thermal pads.

    If you want to use something like Apple used on the VRAM and VRMs. Taking out the guesswork for the thermal pads. You can use K5-Pro. Correct thickness thermal pads perform better but the K5-pro is easier.

    As with any paste. Wipe all areas with alcohol and wear gloves. The stuff isn't easy to wash off. More importantly you don't want to contaminate any surfaces with your finger oils. Be very careful with the pads as everything wants to contaminate them.
     
  11. The.316 thread starter macrumors 65816

    The.316

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    #11
    Ended up ordering this:

    http://www.computer-systems.gr/en/content/product/k5-pro-k4-pro-set-new-package
     
  12. jtara macrumors 68000

    Joined:
    Mar 23, 2009
    #12
    I actually had never heard of thermal pads. So, I did some research.

    Watch this before you use thermal pads!



    No thermal paste at all did a better job than thermal pads.

    He actually tried toothpaste!

    (FWIW, he has tested peanut butter and oreo cooking filling in the past.)
     
  13. velocityg4 macrumors 601

    velocityg4

    Joined:
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    Location:
    Georgia
    #13
    The video is showing a completely different use for the thermalpad than being discussed. The video is using it for a CPU which has a high thermal load (high watts) over a tiny area. The VRAM is much lower watts spread over a wide surface area.

    The VRAM along with VRM need the thermal pads or K5-Pro because they have an air gap with the heatsink. This is because the GPU itself needs a press fit for more efficient thermal transfer. So, the other components have some leeway to prevent obstruction. The thermal pads or K5 just fill the space to allow the small amount of heat to transfer from the VRAM to the heatsink. It's even mentioned at 8:33 how it works well with the VRM on a 1080 Ti.

    He's also using a 0.5mm pad. Which he states is for the GPU VRM and was unable to get a CPU specific thermal pad. Which still likely aren't as good as thermal paste. Since paste is just supposed to fill tiny imperfections in the CPU/GPU surface and heatsink. Even if he had a CPU pad it would be much thicker than paste in a properly tightened CPU/GPU.

    Regular thermal paste can't be used on the VRAM because of the air gap. It would just run. Also if you used a 0.5mm thick application of thermal paste. It wouldn't perform much better than a decent thermal pad. As a good thermal pad has a higher W/mK rating that many thermal pastes. Thermal paste works so well because of the press fitting squeezing it into fine voids. Which a pad won't compete with. The direct cpu to heatsink with no pad also works better than that thermal pad. Since you are still getting a lot of metal on metal contact.
     
  14. jtara macrumors 68000

    Joined:
    Mar 23, 2009
    #14
    Stupid design. But, I gather - popular?

    Either put those cute little individual heatsinks on the VRAM, or give them their own common heatsink that's not part of the GPU heatsink.

    Do the pads have a metal core? Or is that an option?
     
  15. The.316 thread starter macrumors 65816

    The.316

    Joined:
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    #15
    So this seems positive so far:

    D2827FAC-084F-420A-A3D0-085F46312573.jpeg

    Did the bake technique. Preheated the oven to 200c, left it in for a bit more than 9 minutes, let it cool half an hour, added the right pastes, and put it all back together. I’ll see what happens after reloading Photoshop, and doing some work on it.

    Someone who posted a video on YouTube, about how to do the bake technique, said that it’s been working for him for the past 30 months. Fingers crossed.
     
  16. jabbawok macrumors 6502

    jabbawok

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    #16
    Congrats. It’s very satisfying when you recover something like that. I would recommend doing whatever you can to keep the whole thing cool. I assume you gave the heat sink and fan a good clean.
     

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15 July 30, 2019