quessir gave me an old 8800 GTS last year. I've been scrounging together the parts for a secondary PC recently and unearthed it, only to find that it was suffering from colourful but intrusive stripes down the display. Other symptoms included alien hieroglyphs on the BIOS screen and windows being unable to install/update drivers. After
doing some reading, I decided to strip down the card and throw it in the oven to reflow the solder joints. Long story short, it worked. Details below...
1. Remove the covering. On the model I had, there were 4 screws, 2 covered by brand logo stickers.
2. Remove the cover/fan/heatsink assembly and the backplane. There are 8 large screws on the rear of the card and the backplane had a single screw and 4 bolt-type things on either side of the DVI connectors that I used a pliers to unscrew. Don't forget to unplug the fan power cable from the PCB!
2b. Remove the square support heatsink surrounding the cpu. This is fixed on with 9 small screws on the rear of the card.
3. Remove thermal paste from all sections of the card. I scraped off the heaviest portions, then used meths (methylated spirits) to clean the top of individual chips.
4. Pre heat oven to 195degC.
5. Put a layer of tinfoil on a baking tray and use some more to make 3-4 small balls to support the card.
6. Rest card on tinfoil balls. I have seen vids for both orientations, but chose to bake mine GPU side up.
7. Once the oven reaches temperature, bake the card for 8-10 mins. (We have a fan-assist oven, so I gave it 6 mins.)
8. Remove and leave to cool for a few hours. Some people say overnight; I gave mine about 3 hours.
9. Put new thermal paste on appropriate sections of card and reassemble.
10. Reinstall, cross fingers, and boot to check results.
Some people say the running temp has improved on their card. Others say this has only ben a short-term fix, with the card 'dying' again after a month or two. I have seen comments that this fix is repeatable, but would view it as a stop-gap to buying a new card or keeping an old system in operation.
Since the reflow process is carried out in industry, there shouldn't be any component on the card that will suffer much from this procedure. Capacitors that are rated 105degC are (supposedly) tested at much higher temps for shorter periods - the rating is for continuous long-term temperature endurance. That said, I wouldn't do this with a card that wasn't destined for the recycling bin anyway ^^