2009 27" iMac GPU soft gasket material?

[CooperBox]

In the past I've successufully resurrected the graphics card on a 2009 and 2011 27" iMac, with both still functioning perfectly for well over a year with family members. My aim was to get approx 3years additional use from these iMacs.
I've recently acquired another 2009 27" iMac. The previous owner claims that a friend changed the defective graphics card for a Radeon HD4850 purchased from AliExpress, resulting with no image on screen after boot. This is what I found on removal, a mix of thermal paste and "heaven-forbid" a large blue thermal pad!

Not surprisingly I'm unsure of the serviceability of the ex Ali-Express graphics card, but observing the above, not surprised that a problem still exists as I also found the card was not correctly torqued down (screws found finger-tight) and no soft gasket shield installed around the GPU.
Next photo shows where that soft fabric-like gasket should be installed when it's present:

I therefore need to fabricate a suitable gasket from a similar soft fabric-like material as the original (sketch made below). Could anyone please advise on a suitable material, and ideally the thickness.

 

[Nguyen Duc Hieu]

I therefore need to fabricate a suitable gasket from a similar soft fabric-like material as the original (sketch made below). Could anyone please advise on a suitable material, and ideally the thickness.
View attachment 2020388

Try the yellow sponge you can find in the kitchen. If it doesn't melt when you boil it, it will do the job.
Thickness is about 1.5mm, or 2mm

 

[CooperBox]

Hi, thanks for reply! I hoped you see this, as from previous posts I've observed that you're very well informed about iMacs in general.
I've just performed the 'boiling water' test (3 times over several minutes) and this material shows no deterioration whatsoever, so should prove to be ideal for the task in hand. The thickness looks good too and compresses well.
When all's completed, just for general info I'll advise back on whether I was able to resurect this particular graphics card. If faced with failure, do you have any contacts from where to source another good card? I'm in Europe - SW France.
Cheers!

 

[Nguyen Duc Hieu]

Hi, thanks for reply! I hoped you see this, as from previous posts I've observed that you're very well informed about iMacs in general.
I've just performed the 'boiling water' test (3 times over several minutes) and this material shows no deterioration whatsoever, so should prove to be ideal for the task in hand. The thickness looks good too and compresses well.
When all's completed, just for general info I'll advise back on whether I was able to resurect this particular graphics card. If faced with failure, do you have any contacts from where to source another good card? I'm in Europe - SW France.
Cheers!

I had two of them. When the first one failed, I sent it to a laptop repair shop for baking on a professional chip rework station. It didn't work out.
When the second one failed, I just replace it with a M6100, not bothering of re-baking, even if the reworking would cost me only 5$.
Before rebaking (re-working), the repair shop's technician had carefully removed that sponge. He re-attached it afterward.

 

[The_Croupier]

View attachment 2020346

Now I think I’ve seen everything, sheezch.

 

[CooperBox]

Things progressing reasonably well with this refurbishment.
I located a yellow/green sponge from the kitchen. I'll also need an Energizer CR2032 button battery, as with the motherboard removed the original installed BR2032 was measuring less then 3v.



I'm sure I'm not the only one to notice that the BR2032 variety are difficult to find. I've used CR2032 before as a direct replacement with no adverse affects. I understand that these batteries have slightly different chemical make-up with the BR3020 having a higher temperature environment advantage.

With the motherboard removed, thought this would be an equally good opportunity to renew the CPU thermal paste.





To be continued.......

 

[CooperBox]

Update: Rework completed.
Tracing my template, tearing the green scouring pad from a kitchen sponge and making a gasket was fairly straight forward:-


Then installed a fresh CR2032 PRAM coin cell battery onto the rear of the motherboard (yet another irrational Apple design, possibly to discourage 3rd party repairers):



That was followed by a clean install of High Sierra onto a new Crucial SSD (replacing the original HDD).


Note: the ODD cooling fan at bottom right now provides far more efficient internal cooling with the optical drive permanently removed. The re-attached temp sensor still provides a reading in that zone.


With everything cleaned up correctly, given that the video card was allegedly purchased from AliExpress and the improper manner by which it had been installed, my dilemma was whether I should bake the card first, or just correctly paste-up the Radeon HD4850 graphics card and install ‘as-is’ in the chance that it would be detected. I went for the latter option.
That turned out to be the wrong choice, as after painstakingly repasting the CPU, and then the GPU with K4Pro and an abundance of K5Pro together with my new gasket, and reinstalling everything, although the iMac booted it still failed to detect the video card - which frankly didn’t surprise me after reading of bad experiences with used AliExpress cards.
So as I had nothing to lose, I removed the video card (the quick and dirty way - without disturbing the motherboard), and decided on an oven bake, reasoning that the card would either ultimately be deader-than-dead, or resurrected. I wasn’t optimistic, but again cleaned the card of all thermal paste debris and performed the bake. (For the baking process I methodically respected a reasonable oven pre-heat time prior to inserting the card and also a controlled cool-down period. On completion the card was again repasted with fresh K4Pro and K5Pro then reinstalled.

Just prior to reinstalling the screen I found the V-Sync screen flex cable difficult to insert into it's mating socket and on close inspection found damage to the end copper strips.

This was something I’d seen before on another 2009 iMac, and previously rectified with a minute dab of superglue - a fiddly task performed under x10 magnifier as each copper strip is less than 0.5mm (0.019inch). Cable was also then reinforced by the addition of Kapton tape.
Finally with everything reinstalled, holding my breath I pressed the power switch. Et voila! It booted into High Sierra to which I added a favourite desktop image.


The fans too were behaving themselves and not running at max rpm as I’d very simply short circuited the original HDD temp sensor connector with a home-made jumper wire.


A few fine-tuning steps included:
i) deletion of ODD to provide greater cooling efficiency within the iMac
ii) enabling trim support for the new SSD
iii) tweaking down screen resolution to 1920x1080 (probably overkill, but far more confortable for my ageing eyes)
iv) manually setting Macs Fan Control ODD and SSD fans to a constant 2200rpm, with CPU fan remaining on Auto control.

iMac reburbishment completed.

So in summary, this certainly turned out to be a bitter-sweet exercise. Many detractors will no doubt scoff and say, “Why bother, just buy new”. However I’ve great satisfaction in knowing that this upgraded iMac now performs better than new, is capable of most general tasks from photo/music/video editing and very satisfactory web browsing with current FireFox 102.0 browser. In addition to learning a little more about these amazing, very upgradeable machines, I’ve also saved this from the crusher and inevitable landfill.

 

[The_Croupier]

Just a question, why do you think you removing the ODD is improving cooling?

The ODD is designed to assist cooling of the GPU to directly channel air flow to the GPU radiator fins. You essentially now have a void where the air tunnel used to be.

Unless you plan on using that space for something I would advise to put the ODD back even if it’s defective.

 

[CooperBox]

Just a question, why do you think you removing the ODD is improving cooling?

The ODD is designed to assist cooling of the GPU to directly channel air flow to the GPU radiator fins. You essentially now have a void where the air tunnel used to be.

Unless you plan on using that space for something I would advise to put the ODD back even if it’s defective.

I believe that without the ODD the whole zone is kept cooler - both the radiator and the GPU card itself, as there is less restriction of cooling airflow. Adding to this belief is that this is the 4th similar iMac I've rescued, 3 of which are still in regular use, whereby with the very first attempt I left the ODD in situ and all functioned correctly for just over a year, after which the GPU failed. Granted that may possibly be due to my initial limited use of KP5 paste on the card, which since that event I now ensure is pasted on in great dollops.
I agree that there's a fair amount of controversy on the right and wrong way to restore these iMacs with a defective video card, and although I'd never pretend that my workaround is the definitive method, what I've described above has definitely given a very satisfactory prolonged life on similar iMacs I've worked on.
Should this current refurb not stand the test of time, I'll certainly report back.

 

[Nguyen Duc Hieu]

Just a question, why do you think you removing the ODD is improving cooling?

The ODD is designed to assist cooling of the GPU to directly channel air flow to the GPU radiator fins. You essentially now have a void where the air tunnel used to be.

Unless you plan on using that space for something I would advise to put the ODD back even if it’s defective.

Totally agree.
If the ODD is dead, just disconnect it from the logic board is enough.
Or better yet, there is a cheap caddy bay you can buy and install another SSD to the position. Remember to buy the thick one (9.5mm or better yet, 12mm)

HIGHFINE Universal 9.5mm SATA to SATA 2nd SSD HDD Hard Drive Caddy Adapter Tray Enclosures for DELL HP Lenovo ThinkPad ACER Gateway ASUS Sony Samsung MSI Laptop

HIGHFINE Universal 9.5mm SATA to SATA 2nd SSD HDD Hard Drive Caddy Adapter Tray Enclosures for DELL HP Lenovo ThinkPad ACER Gateway ASUS Sony Samsung MSI Laptop

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