Replacing Nvidia 8800 GS on 2008 imac: Tips/Guide

Discussion in 'iMac' started by twistedbydesign, Sep 13, 2012.

  1. twistedbydesign, Sep 13, 2012
    Last edited: Sep 14, 2012

    twistedbydesign macrumors member

    Oct 15, 2008
    I'm writing this guide because these drives seem to have an extremely high failure rate. My 2008 imac (2.8Ghz intel core 2 duo processor) had the card fail on me not too long ago so I set out to find a solution.

    There is a lot of conflicting data on whether the graphics card in the imac is replaceable. This stems from the fact that many of the older generation imacs have the GPU soldered to the logic board. This is NOT the case with the 2008 24 inch that has the card mentioned above. It is very difficult to get to. But with planning, patience and care, it can be replaced. Since there don't seem to be any guides for this particular generation and the failure rate of these cards is so high, I figured I'd take the liberty of posting some tips and references for changing this card. I was going to do a step by step guide, but the ifixit guide is pretty much all you need.

    I replaced my Nvidia 8800 GS with an ATI Radeon HD 2600 Pro. The product number for the ATI card is 661-4663. This card was a direct drop in for the Nvidia Card. I ordered it from memory4less and it came with the heat sink. There are a lot of sites that claim to have this card, but after ordering I got a notice that it was not in stock. Memory4less was more expensive, but the only place I could find that actually HAD it. The ATI card is 256mb as opposed to the 512mb that the Nvidia card has. It's definitely a bummer to downgrade. But the ATI cards seem to be rock solid and I don't notice any performance issues since the switch.

    It was noted by another poster that some of the ATI cards may cause freezing issues for some users due to a driver problem when using Lion or Mountain Lion. I use snow leopard and I have not personally had this issue. But it is something to be mindful of.

    Keep in mind, this is NOT a quick fix. It takes a LOT of time and careful handling of sensitive components of the imac. I'm not the most tech savvy person in the world. But I'm very patient and methodological which helped me to get through this with no major issues.

    I don't have any pictures because at the time I replaced the drive I wasn't planning on making any sort of how-to. I also don't have screwdriver sizes or anything like that. I just had a box full and had to pick out whatever fit. However, I used this ifixit guide for replacing the graphics card in an older intel 20 inch imac.:

    While there are a few small differences in some steps, this guide was extremely helpful for me. If your card already has the heat sink attached to it, as mine did, You only have to go up to step 38( after that it goes into placing the old heat sink on the new card.) This guide also has screwdriver sizes listed. But please note that the screw sizes and placement will not be exact since that guide is for the 20 inch.

    A few tips:

    -In order to get the glass panel off my mac, I used two suction cups from GPS stands that I had lying around. If you are careful, you can do it with just one, but two is a bit easier. This is cheaper than buying suction cups for a one time job.

    -There are probably 10 to 15 DIFFERENT types of screws. Make sure you have a system of keeping track of all the screws and where they went. I printed off pictures of the logic board and numbered every screw I took out then layed the screw on a piece of paper with the number next to it. Some ppl have used baggies to label them. This is very important because even screws that parallel each other can be different sizes.

    -Avoid touching the LCD panel. I got a few prints on mine and it took like 10 mins of gently wiping with a microfiber cloth before I could get it clean again.

    -When Rescrewing the LCD panel, don't screw it in too tight or you will get increased backlight bleeding on your display. I had to take the glass off again and readjust the screws.

    -The LCD Panel is plugged into the logic board. Re-plugging this part in was the most difficult part for me of the whole thing. I had to have my roommate Hold up the panel while I tried to get it plugged in. It's such a strange angle and it's a pain. Fair warning.

    -Also, compressed air is a must. It'll give your imac a nice cleanin, and will help to keep dust from settling on the LCD or the glass (spray frequently, but be careful!)

    -The placement of the screws to remove the logic board are somewhat different from the guide. I did have a paper that I printed off and labled which screws I took out, but I threw it away since it was scribbled all over (and, once again, I wasn't planning on writing any guides).

    -Don't forget to remove and replace the memory before and after taking the computer apart.

    Along with the ifixit guide, I wrote in a notebook EVERYTHING that I unplugged from the logic board before unscrewing it. In fact I would suggest writing down every step in the entire process so that you can easily work backwards when its time to reassemble. There are a lot of things to unplug. I will list them off here, along with descriptions.

    I would suggest printing off this list and checking each item off once during disassembly (when you unplug it), then once again during reassembly. This will help to prevent you from forgetting to plug something back in and having to take everything apart again. I'll include the descriptions I wrote in the notebook. They aren't very techie sounding. I kept them very basic so I didn't get mixed up. Some of these are different than the ifixit guide, which is why I am adding the descriptions. I dont know how consistent the 24's are inside, but hopefully this helps.

    Items unplugged from Logic board/Location on logic board:

    Left Speaker Wire: Long black wire that leads from the left speaker to the sound card on the right side of the imac.
    Ambient Temp: four tiny wires connected to a small 4 prong plug goes into the very bottom left corner of the logic board
    Power Button: Two tiny black wires connected to 2 prong plug. Located Just to the bottom-right of the CPU fan plug
    CPU Fan: Labeled on motherboard: Located directly above “Ambient Temp”
    SATA Data Cable: Labeled as “MLB”. Goes into Right/middle/Bottom of Logic board. Just to the left of where Blutooth gets plugged in.
    DC-In Cable: Large cable/plug with retaining tabs. This is the largest plug on the board.
    Airport antenna connecters x2: Tiny single wires that pop into the wireless card. Gray goes on top, Black goes on bottom. The wireless card can be identified by the model information and “made in china” written on it.
    Blutooth Antenna: Tiny single blue wire. Pops into golden slot just like the airport connectors. Located to the left of the watch battery on the right side of the board.
    Camera Cable Connector: Labeled on board: Slot is just below the wireless card, slightly to the right. The cable is a single thick black wire with 4 small wires (gray, white, light green and blue) coming out and one slightly thicker black wire. The plug is near wireless and blutooth plugs on the board.
    Right Speaker Wire: Long black wire that goes to sound card. Plug is on top left of soundcard.
    Optical Drive Fan: Slides out Parallel to the board (rather than being pulled up out) This is located just above the soundcard. It is somewhat covered by the optical drive cable.
    Optical Drive cable Clip: Screws in with 2 small screws: there is a small chip on the end of the cable.
    Microphone Cable Connector: Plugs into the sound card just to the left of the Right Speaker Connection.
    Hard Drive Thermal Sensor: Located at the top of logic board Just under hard drive. Comes out parallel to board. Black & Gray cables intertwined to a 3 prong connector.
    Optical Drive Thermal Sensor: Right next to hard drive thermal sensor. Two black intertwined wires. 2 prong: Goes in Parallel
    Hard Drive Fan: Labled: Next to Optical Drive Thermal Sensor. 2 black wires, one brown wire, one gray wire. 4 prong. Goes in parallel.

    Using these tips and the ifixit guide, you should be able to replace the card without much of issue. As stated, there are some differences in some of the connecters and screws/screw placements. I just eyeballed this for the most part and was able to get through it without any problems.

    If anyone does decide to attempt this, I would suggest taking pictures and noting differences from the ifixit guide and posting them on here to help anyone else that decides to replace their card.

    I'll be sure to update this with anything else I might think of. I realize that this is a bit longwinded for not being an actual step by step guide. But I do hope this helps for people who are considering replacing the card.
  2. Intell macrumors P6


    Jan 24, 2010
    Do note that some people have had freezing issues with the ATI 2400/2600 in the iMac7,1 and iMac8,1 on 10.6.7 and higher, including Lion and Mountain Lion. The freezing is basically everything freezes except the mouse courser. Non-GUI things like sound and network file sharing still work. Another type of this freezing is when the screen is black and usually happens when waking from sleep. This freezing is a driver problem that Apple apparently knows about, but has not yet fixed.
  3. twistedbydesign thread starter macrumors member

    Oct 15, 2008
    I wasn't aware of this. I use snow leopard. I added a notice to my initial post. Thank you for the info!
  4. Johnf1285 macrumors 6502a


    Dec 25, 2010
    New Jersey
    Awesome guide.

    One question. Did you attempt to salvage your 8800gs?

    I read online that a few people were able to "resurrect it" in a sense by removing the heat sink and baking it in the oven around 400 degrees or so, with the solder/trace side facing upwards, allowing the solder to flow through each trace again.

    Not sure if this method works every time. I am also curious too because I use to own this same exact iMac, so shocked to learn about the poor reliability on the 8800gs :(
  5. moab macrumors newbie

    Sep 13, 2012
    @Intell My NVIDIA GEFORCE 8800 GT has just recently died and after talking to twistedbydesign I decided to replace it with the same ATI he used, following his amazing guide.
    I wasn't aware of these issues with Mountain Lion though, which is the OS I want to use. So I'm wondering, do you know of any other cards compatible with iMac 8,1 24" 3.06GHz from early 2008 (A1225) that don't freeze with Mountain Lion? Or what drivers should I use to make the ATI run smooth?
  6. twistedbydesign thread starter macrumors member

    Oct 15, 2008
    I read a few reports of people claiming that they could be "baked" back to life. But I didnt want to take any chances. I think I remember reading that it was a temporary fix for several ppl but that the card crapped out again before long. I have heard very few reliability issues with the ATI card so i decided to stick with that. My imac is mostly just used for browsing, garageband and as a media center. So I wasnt too concerned with having to downgrade the card.


    I did a quick search and found this:

    these people don't seem to have any issues with the card and mountain lion. None of them have your exact mac. But a bit more research into some testimonials of ppl with the ATI card might put your mind at ease or shed some more light on potential issues.

    perhaps there is something else related that may be causing some ppl problems.
    Intell: Where did you hear about this issue?
  7. moab macrumors newbie

    Sep 13, 2012
    That's very reassuring, I have 4GB RAM and 3.06GHz, so it looks like it should handle Mountain Lion. Also, apparently some ppl there are using the 256mb card for gaming and design stuff and it works OK.
  8. twistedbydesign thread starter macrumors member

    Oct 15, 2008
    Oh! another thing I'll add above. Don't forget to remove the memory and don't forget to put it back in.
    I forgot to reinsert the memory after I was done and my heart stopped till i realized that that's what the problem was. lol
  9. Intell macrumors P6


    Jan 24, 2010
    I'm not saying every ATI 2400/2600 is having freezing problems with 10.6.7+, only some cards are. There are only three video cards that will work in a 7,1 and 8,2 iMac, the ATI 2400/2600 an the Nvidia 8800.
  10. moab macrumors newbie

    Sep 13, 2012
    It looks like there's a few cards that will work with iMac 24". I'm not sure what's that Airwall thing, anyone knows about it?
  11. moab macrumors newbie

    Sep 13, 2012
    Ok, it's just an anti shock mount, I don't know why is listed everywhere as a video card.
  12. twistedbydesign, Sep 14, 2012
    Last edited: Sep 14, 2012

    twistedbydesign thread starter macrumors member

    Oct 15, 2008
    Interesting. Are you going to try a different card than the ATI? If you do please let me know the results!
    I think intell is correct that only those few cards are interchangeable. I definitely wouldnt bother trying another 8800 GS. They seem to timebombs.
  13. moab macrumors newbie

    Sep 13, 2012
    I might try the GeForce GT130 just because it's 512mb. I'm not sure whether I should trust NVIDIA anymore though. Does anyone know of any issue with this card?
  14. Johnf1285 macrumors 6502a


    Dec 25, 2010
    New Jersey
    I know... all these Nvidia problems have me worried if the next gen iMac uses Nvidia whether or not it'll suffer similar issues.

    I've had a few Nvidia cards in the past, in laptops, windows pc's, etc., and luckily haven't had any problems. Knock on wood!
  15. twistedbydesign thread starter macrumors member

    Oct 15, 2008
    Seems to be mostly an issue with this particular GPU. I haven't heard many bad things about Nvidia overall.
  16. Leind, Oct 5, 2012
    Last edited: Oct 5, 2012

    Leind macrumors newbie

    Oct 5, 2012
    Thanks a lot for the above information. Very useful.

    I will add my 2 cents :

    A video explaining the removal of the Motherboard. Once the motherboard is removed the video card is very easy to remove (2 screw on the card and one on the Heat sink, and a temp sensor cable) :

    Also, I can confirm that reflowing the 8800 card is working. But it may not least long. My Imac is now working for the time being after "baking" the card at 240 C° for 6 minutes (Before it was not even booting up, and I had yellow vertical bands every 2 cm).
    My experience with Laptop GPU is that it can last from 2 days to 6 months. Since the Imac is stationary it can help, as vibration and movement when the GPU is hot are very bad.

    So I'm looking for another solution.

    One would be a software to control the Imac ventilator. The 8800 solder is in fact sensible to rapid change of temperatures, especially when cooling off rapidly after heavy use. So fine-tuning the ventilator speed, or at least setting arbitrarily the ventilator on high all the time would help. I know that Thinkpad users have had some success with this method for similar Nvidia GPU issues.

    Does someone know if such software exists?

    (More details : After the EU banned the use of dangerous chemicals in electronics to facilitate recycling (RoHS directive), Nvidia amongs many others had to switch its solder formula.
    They got it wrong, and the solder they used at first was very sensible to brutal change in temperature. A whole generation of Laptop GPU were affected and were litteraly timebomb. The bad years were 2007 to early 2009, depending on the video chip. After they switched the manufacturing process things got back to normal. )


    Also waiting on the results of the GeForce GT130 and other cards.

    This card should be OK regarding the solder issue since they were launched in march 2009.

    twistedbydesign, could you tell me if the 8800 Heatsink was the same as the 2600 Pro?
    I am considering the purchase a naked 2600 Pro and would like to know if I can reuse the original heatsink.
  17. twistedbydesign thread starter macrumors member

    Oct 15, 2008
    Keeping the Nvidia card would definitely be ideal (no need to spend a LOT of money on a technically inferior card, lol).What exactly is in that the baking does to the card? If it has to do with the solder is there any (easy-ish) way to just completely resolder certain parts so that the heat/vibrations arent an issue? If it's the type of solder they use, could you just suck up the faulty areas and re do them?

    My only concern is that the imac is suuuuch a pain to take apart, I'd almost prefer the peace of mind of replacing the card rather than chance having to take it apart again.

    Thanks for your contributions!
  18. Leind macrumors newbie

    Oct 5, 2012
    There are micro-fractures forming inside the solder, which eventually cause the card to fail.

    By reflowing the card, you briefly melt the solder, and get rid of the fractures. The problem is that an oven is not ideal, ideally you would need professional equipment able to control precisely the temperature, as if you overdo it the solder will be bristle. But it's the cheapest way to fix a card.

    Replacing the solder is not possible. Perhaps feasible with professional equipment, but replacing the card would be cheaper anyway.

    If you don't game, I don't think you will notice any difference between the two cards. I'd rather change the card too. Do you remember if the 2600 heatsink was the same as the 8800?
  19. twistedbydesign thread starter macrumors member

    Oct 15, 2008
    The one i bought came with a heatsink. They looked identical from what I remember though.
  20. razorme macrumors regular


    Jul 16, 2002
    Calgary, AB
    I'm resurrecting an old thread because there are probably still people out there looking for help. I just had my 2008 iMac w/3.06 & NVIDIA 8800GS fail.

    I brought it to Apple and they quoted $200 to repair. I'm guessing this $200 repair is subsidized because it was only $39 for labour despite the time it takes. Unfortunately once they started, they refused to continue because they saw that I had been inside the iMac to replace the failed Apple Hard drive (failed in 2012).

    So I decided to try baking the card. I used the iFixit guide without too much trouble. I removed the heat sink and baked just the card itself at 400 deg F for 10 minutes, let it cool for 5 minutes, then baked again at 400 deg F for 10 minutes. I wanted to be aggressive and make sure the solder melted so hopefully the fix would last a long time.

    I replaced the thermal paste and put back together (removing all the smudges Apple left on the glass cover too). It is working great!!!

    I installed smcFanControl to increase the minimum RPM of the CPU fan from 1200 to 1600 rpm. I tried a much higher RPM but it doesn't seem to really make a big difference to temperatures but sure is noisy.

    If you have the time, rebaking the card is an option. Be careful!
  21. JackRM, Aug 15, 2013
    Last edited: Aug 15, 2013

    JackRM macrumors newbie

    Aug 15, 2013
    Hi guys,
    I also got a 2008 24" 3.06 iMac with 8800GS
    After all adventures with my card (baked 3 times) and each baking was good for 3-6 months. Finally (I hoped so) I bought a new chip and made it swap in a specialized laboratory (as I've been told that should be the best solution).
    Today my card failed again after 6h of fullscreen movie watching (ambient temperature was 27C/81F) with its usual boot artefacts and so on as the photo attached.
    Now it's been a 3 years of baking the card and I'd like to drop this damn card and swap to another one.

    Do you have some feedback or info if I can put in the GT130 card in my iMac ?

    I'm considering buying the naked gt130 and fitting to the existent 8800's heat sink.

    Thanks in advance.
    Jack, Italy

    Attached Files:

  22. Intell macrumors P6


    Jan 24, 2010
    See the other tread you posted in for the complete list of compatible iMac7,1/8,1 cards. There are only three and the GT130 is not one of them. Maybe you should start your own thread on the subject.
  23. tvsp macrumors newbie

    Dec 8, 2010
  24. razorme macrumors regular


    Jul 16, 2002
    Calgary, AB
    FYI - my iMac still works great nearly 8 months after doing an aggressive double-bake. If it does fail a second time in the future, it will be time to move on as it is getting quite outdated, although it does run Mavericks just fine.
  25. henry99 macrumors newbie

    Sep 11, 2014
    iMac 2008 EMC 2211 - double baking succeeded!

    Hello to all,

    I would like to thank you all so much for this discussion and for sharing "baking experiences" for nVidia 8800GS card and my 2008 iMac. I'm so grateful to you for your help that saved my beloved computer.

    Few weeks ago nvidia graphic card broken on my 2008 iMac EMC 2211, on local Apple repairing service they told me that this model is not supported any longer since it is more than 5 years old.

    So disassembling and trying to "double-bake" my broken nvidia card was one of the very less options available.

    I decided it is worth a try, then carefully read few tutorials, because for example unmounting logic board and few other details were little bit different on my iMac than it the attached tutorial by twistedbydesign, but I succeeded to reassembly it and...

    ...and my iMac started to work again... now it's almost 2 months and I hope it would last...

    razorme: I just wonder is your iMac still working?



    razorme: I just wonder is your iMac still working?

Share This Page