[Hallicrafters] Temperature Compensator??

[Wayne Light]

I'm recapping my Sx-71 and noticed that on the OD-3, pin 7 there is a capacitor listed as T.C. 
 I don't have a clue what this is. It is noted as a capacitor but in the parts listing there is no value listed...and I can't find one, on the radio.
 
How important is this part? What does it do? 
 
Hope some of you old timers will take a minute and educate me.
 
Thanks Guys,
 
Wayne