I had a go with a 1200w heat gun (hot air blower) normally used for stripping paint on my nvidia chip. First covering the whole logic board with tin foil -folded many times, then cutting a small square hole in the foil where the nvidia chip is.
i tested the heat gun in the air on lowest setting, and gauged how hot it was with my hand from a distance. At about 50 cm distance it was unbearable after a second or two.
From around 20-30 cm distance i gently heated the whole board from above, moving the air gun over all of the foil. I did this for around 2 mins.
then I focused a bit tighter on the nvidia chip, at around 20 cm, for 3 mins, at which point i could smell the solder a little and then another minute a little closer. So a total of 4 mins at fairly close range to the nvidia chip. I think the key here was that I could smell the solder / electronics when it was 'cooked'. I was VERY scared to over cook it and end up with one big blob of solder underneath. I left the logic board to cool after heating - after reading you mustnt move it. Reassembled it into my A1226 Macbook pro and its working fine. Ive adusted my energy preferences in be powersaving. I hope the fix lasts..time will tell.