A cathode-ray tube (CRT) assembly of a projection television includes a CRT for creating an image, a lens for magnifying the image created in the CRT and projecting the image onto a screen, and a coupler disposed between the CRT and the lens. A cooling liquid receptacle is provided within the coupler, and is filled with a cooling liquid. For that purpose, a cooling liquid pouring inlet is disposed on one side of the coupler for pouring the cooling liquid into the cooling liquid receptacle, and an oilpack is connected to the cooling liquid receptacle so that a portion of the cooling liquid is contained therein when the cooling liquid in the cooling liquid receptacle expands due to heat generated by the CRT. The oilpack comprises a sealed space, a pack holder disposed between the sealed space and the cooling liquid pouring inlet, and an oilpack coupling mechanism formed on the pack holder.