Juuuust a minute!
The smelling can be signs of a small disaster to come!
The resistor in the power pack should not get too hot because the power requirement for the SM 100 series of motors is very low.
First, the micro switch that sticks is the red (or sometimes black) one in the picture:
In that picture, you also see three yellow capacitors with a value of 0.068uF, 0.33uF and 0.01 uF.
These three safety caps (X2 safety factor) tend to develop cracks in the plastic over the years. Once cracked, they soak up humidity and given time, will short out. This will go off like a firecracker, stink to high heavens and make a mess - which is the reason they are given the pet name Firecrackers...
Any unit with these Rifa caps (not only Dual...) should have these replaced ,if cracked, for that reason.
The heat developed in that resistor is a good sign that the C2 (and C3 if present) is starting to go.
Replace all of them for piece of mind!
Klaus Adlhoch, fmr. Assistant Service Manager,
Noresco -N.Q.I.-Dual of Canada,
Area of expertise: Tech Training and Consumer Service P.R.
Associated with Dual till Thompson era.
Favorite Duals: TG 12a, 1009, 721.