Abstract: The heating unit for sealing vacuum electron tubes of the type having a glass stem, a glass exhaust tubulation extending from the stem and a plurality of electrically-conducting leads extending from the stem in a circular array around the tabulation includes a cylindrical heating coil within a coil recess of an electrically-insulating coil support. The coil recess circumscribes a central aperture within the coil support. The coil support has a first and a second surface with a coil-positioning lip projecting upwardly from the second surface thereof and circumscribing the central aperture. A hollow, substantially cylindrical, tubulation-locator having an outwardly extending flange formed in an outside surface thereof is disposed between the second surface of the coil support and a base plate. The locator also includes a centering collar formed in its outside surface and a tubulation centering aperture formed in the inside surface. A top plate is adjacent to the first surface of the coil support.