Uploaded April 2020 | Updated September 2026, 2 weeks ago

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Although my 2nd bake lasted 2 years 9 months, my 3rd bake lasted only a week, and my 4th bake even with brand new K5 Pro too lasted only a week. My 4850 has reached its bake limit. In this video I describe what I am planning next and how that correlates with my past videos on the subject.

🍎 Apple Forum Discussion about replacement video cards that work in the late 2009 27" iMac: discussions.apple.com/thread/3029120

♨️ My 2nd, 3rd and 4th bakes of the Radeon 4850 video card were done in a convection oven at 200°C (400°F), baking the card for 10 minutes. I use aluminum foil stand-offs to ensure hot air flow beneath the card.

🏥 Defective Video Card Symptoms. In my case, the iMac wouldn't boot fully and would freeze at the Apple logo screen with the progress bar only 50% finished, sometimes with screen artifacts. At times when it would boot to the desktop, there were artifacts that made using the computer impossible. In the case of my 3rd and 4th bakes though, the problem was the screen would stay dark.

🛠 TOOLS to open/close iMac:
• 2 strong suction cups for front glass removal: amzn.to/2tkcmvJ
• Torx T10 for LCD removal (T9 works but T10 is best) & T9 for video card removal. The following kit contains more than needed for the iMac, but it's highly rated, has grippy handles and magnetic tips, and no 1 month+ wait from China: amzn.to/2UCaurK
-or-
Alternative kit, WRENCH style (cheaper): amzn.to/2wIgWWe
-or-
Alternative kit, BIT style (you'll need a handle): amzn.to/2vRkUeC

🔦 OTHER ITEMS needed or recommended:
• Thermal Pastes (2 types REQUIRED!)
K4 & K5 Pro Kit: amzn.to/38WkEZO
-or-
K5 Pro (for chips other than GPU): amzn.to/33OIDJ6
& Thermal Grizzly Kryonaut (for GPU only): amzn.to/36NMQwu

• Anti-static wrist strap (connect wire to earth ground): amzn.to/2uSTy74
• Dust blower - Giottos Rocket Blaster Large: amzn.to/2OgHHXt
• ISO Alcohol 99% (to remove old thermal paste): amzn.to/2YsK8v3
• Swabs & Tissues (for cleaning off the old thermal paste)
• Microfiber cloth (for cleaning the screen/glass)
• Flashlight (to peer into the dark spaces inside the iMac)
• Aluminum Foil (make feet to raise up video card in oven)
• OVEN set to 200°C/400°F (without which, this repair is in vain)
• Time & Patience

🔌 IF NEEDED: Replacement Ribbon Cables:
• BIG (Amazon): amzn.to/32Ygv7s
• SMALL (Amazon): amzn.to/33ZEvX4
• BIG (AliExpress🇨🇳): bit.ly/2AdHvCV
• SMALL (AliExpress🇨🇳): bit.ly/2zRDbIC

💵 NOTE: Your price on Amazon (US only) is the same even if you don't click the "amzn.to" Affiliate links above, but if you do kindly click and purchase within 24 hours, Amazon may pay me a small commission on all qualifying items in your Cart (even items not linked above).

😎 Fan Control Apps to keep your iMac running cooler (I'm using both on different Macs and can therefore recommend either):
• Macs Fan Control: crystalidea.com/macs-fan-control
• smcFanControl: eidac.de

📷 4850 Card Photos (cleaned):
TOP: https://flic.kr/p/RjLLCd
BTM: https://flic.kr/p/RjLKGf

🎥 All my BAKE videos: bit.ly/2UEOf4o
🎥 2015 MBP 15" Repasting Video: youtu.be/_XQNGNAwrLw

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#Apple #Macintosh #iMac #VideoCard #JDW