"CitizenRuth" wrote in message
news
I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers and
other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an inner
metal frame which was screwed to the outer frame. After removing the
screws, the thing wouldn't budge, until I realized it was "glued" on and
I was able to yank it off with some effort.

The adhesive is white and greasy.

What you have there is very common, it's just silicone heatsink compound,
used to increase the efficiency of transfer of heat from component to
heatsink. If it were thermal *adhesive*, they probably wouldn't have used
screws to secure the assembly. Thermal adhesive is generally used instead of
mechanical fixing methods, and the adhesive itself is rather pricey. It is
very common for thermal heatsink compound to age and can become quite
stubborn to break, which might lead one to believe it's adhesive, but it's
easy to spot the difference as thermal heatsink compound will be softish and
sticky as opposed to rock hard. Thermal adhesive is *very* sturdy though,
it's epoxy based, sets rock hard and can require serious force to remove.

You should clean off all the old compound and reapply new. You *might* get
away with reassembly without new compound, but I don't think it's worth the
gamble. If it isn't convenient to get to an electronics shop for a tube of
heatsink compound, the stuff available for CPU heatsinks, which is readily
available from computer shops, is the same thing. White or silver compound
will work great. You don't have to plaster it on like mortar as some people
believe, just apply a nice even coat to one surface and reassemble.

Dave