[ NOTE: I put Annotations on this video but you can't see them on mobile. Use a desktop computer to view them. ]
► Tools you will need to open and close the iMac:
• Torx T10
• 2 strong suction cups (for front glass removal)
• Philips "+" screw driver (for RAM door)
• Anti-static wrist band
► Other items you will need:
• Dust blower - Giottos Rocket Blaster Large or Compressed Air
• BR2032 button cell battery for use on logic board
• Thermal Paste for GPU heatsink
• Alcohol (I used anhydrous Ethanol)
• Microfiber cloth (for cleaning the screen/glass
• Vacuum cleaner (for those dust bunnies)
• Flashlight (to peer into the dark spaces inside the iMac)
• Sticky labels (yes, you should mark the connectors)
• An oven set to 200°C (without which this repair is in vain)
• Time & Patience
► 4850 Card Photos (cleaned):
► I baked the Radeon 4850 video card at 200°C for 9 minutes. I chose 9 minutes because after reading much about this subject, some people said 8 minutes and others 10, so I took the average, which is 9. It worked for me. Just be sure to use the aluminum foil at the bottom of the board to allow hot air to flow all around the board.
If you use Arctic Silver 5 like I did, don't use to much because if the heatsink presses down on your hefty glob and if it spills onto the tiny capacitors on the GPU chip itself, the silver could short the connections. If you are worried, just buy Arctic Silver MX-4 which is not conductive.
►►► July 11, 2017: Well, my 1st bake lasted all of 4 months. What inspired me to do the 1st bake was another YouTuber who did the same repair and who said recently his iMac had been running fine for 17 months since the repair as of Feb. 2017. Why he got 17 months when I only got 4 months is anyone's guess. The good news though is I have done a 2nd bake and had success. Here's the full video:
Thanks for watching!