Carvin Mixer Board "Component I have not seen before"

[ENB]

My Carvin 1644P powered mixer board has a couple of issues that may be due to have been over heated. This amp has 4 separate internal 300 watt power amps (Solid State). One channel has become distorted. Upon opening the unit up and cleaning out "any" dust I had found with air, I begin to give a close visual inspection. ON the units power output section there is what appears to be 4 transisitors with what appears to be a copper heat sink of copper attatched to a spring steel looking device the size of a small cigarette lighter. The corners of them are soldering into the PC board but is totally isolated form any of the printed circuit. Three of these things hae what looks like a black rubber device nearly the size of a pencil erasure. However one of them has been discolored to a wite color and appears has melted a bit. Am I looking at some type of a thermal protection device? I have asked Carvin for a schematic but not gotten any response.

Just looking for ideas.

ENB