< I have a 10 year old AV receiver that I opened to de-dust. I noticed that on < the heat sink there a black foam material running across the top length of < the heat sink. The foam looks like double-sided foam tape, but is sticky on < one side only.
I've found that some people like to cover any identifiable markings/stampings, etc. with the thermal `white paste'. Also when trying to remove the heat sink the `paste' has a tendancy to tear the pins off of cpu's.
I also believe that some people believe that the thermal paste is a magical item that makes heat go away. I just spent half a day scrubbing the wite paste off the back of an aluminum block that I would like to use as a heat sink. It's kinda like bolting a plastic fan to a GPU - yes it moves the air but if the air is hot enough the pastic will melt. I've found it better to direct air or water through the fins; heat usually goes up.
< I'm not sure what the intended purpose of this was, and if I should attempt < to repair/replace it with something else as it is cracking off.
Then again your talking to someone that uses closepins to keep their transformer from vibrating too much :)
< I could use regular foam double-sided tape, but imagine that the heat sink < get very hot and the tape would get unsticky very quickly.
I believe this is the general idea - keep it sticky and some people (like myself) usually keep away from it.
< Any thoughts on why it would be there in the first place, and what to use to < replace it.
To keep something from vibrating or running very hot?
As an indicator? I use the glue gun sometimes to make sure that a heatsink didn't get too hot. It's like wax but comes off very easily with a dab of alcohol.