Resistor pack thingy?

[LegoHead]

Mine failed over the weekend, managed to get a replacement though.

Just wondering why its called a resistor pack, as it looks like a transistor stuck on a huge heatsink inside. Not got past the white jelly yet.

What does it do?

 

[BrianR]

It regulates the speed of the air circulation fan, you have the late type with the transistor regulated circuit, the early ones had wire wound resistors.