Abstract: For use in the manufacture of a cathode ray tube, an apparatus for testing a hermetic, glass-like frit seal interposed between the funnel and faceplate of an in-process cathode ray tube. The inside walls of the funnel have a conductive coating adapted to receive test voltage which is applied to an anode button located on the wall of the funnel. A discontinuity in the hermetic seal causes a high voltage breakdown in the seal when the test voltage is applied to the cathode ray tube. The apparatus comprises an elastomeric band which is capable of being stretched over the tube, conforming to the shape of the hermetic seal between the funnel and faceplate. It further includes means for supporting and locating the cathode ray tube in a position such that the tube may be tested.