I may not have explained my problem fully. When water is draining into drain cup it will freeze as it drains out forming about 1/4 to 1/2 inch hanging drip. Therefore, the next time it goes through defrost cycle this frozen drip prevents water from draining into cup then into tube and then into evaporator pan. About every two weeks there is a need for the hair dryer to defrost this drip.
Assuming the drain tube is completely clear and draining fast, maybe you can take a bare copper wire and wrap it around your defrost heater and run the other end down the tube. The heat will transfer and keep the water from freezing.
Drain cup freezes 
