Weekly television digest (Jan-Dec 1960)

22 DECEMBER 26, 1960 more about MYLAR TUBE SHIELD: Du Font’s Mylar shield for pic ture utbes (see p. 16) is actually the 3rd route of approach to the laminated-on-the-tube implosion plate —Coming’s & Pittsburgh’s being the other 2. At Chestnut Run, Del. last week we saw much the same presentation & demonstration now being given on request to tube & set makers. Later we talked with representatives of tube & set manufacturers. Du Pont showed us four 19-in. portable sets (they happened to he doctored-up Admirals), each with picture from the same channel, and each one labeled with its weight. Here’s how they lined up: Set with conventional external implosion glass weighed 39 lb. 8 oz.; with Corning laminated cap, 42 lb. 8 oz.; with modified Corning laminated cap (glass flanges clipped oif for mounting in portable cabinet), 40 lb. 8 oz.; with Mylar shield, 36 lb. 2 oz. We compared image on Mylar-shield set with that on conventional external-glass set, with Coming glare-free treated cap and with standard Corning cap in brightlylighted room. Both the Corning treated cap and the Mylar shield sufficiently eliminated reflections (daylight streaming through Venetian blinds) to produce satisfactory pictures. Both surfaces looked similar. Du Pont engineers explained that because Mylar film surface is so close to faceplate, there should be less tendency for the non-reflective surface coating to cut down picture resolution than with implosion plates mounted further from the image. Pictures on all 4 sets appeared identical in color. Implosion resistance: Implosion tests have been made on 2 versions of the Mylar-capped tube — ^with & without a metal band around the periphery of the faceplate. Du Pont officials said that it satisfactorily contained implosions, but added that they didn’t yet know whether such a tube could be characterized as “implosion proof” as is the Corning laminated tube (Vol. 16:50 pl5). Tubes used with Mylar shield so far have been standard Kimble-type 19 & 23-in. “heavy” tubes designed for use with external implosion glass. Du Pont officials said they didn’t know whether it can be used with Corning-type lightweight bulb designed for laminated glass cap. The Burning Issue How about scratching & burning? Again pointing out that outer surface of the shield is extremely close to image, du Pont engineers said this characteristic as well as the light-scattering non-reflective coating minimize effect of scratches. Indeed, we couldn’t notice any scratches as we viewed the Mylar-shield picture. They added that Mylar, while not nearly as scratch-resistant as glass, is the most resistant plastic film made and the reflective coating is even more so. Mylar shield will melt or discolor “if you stoke a cigar up real hot and grind it into the surface,” they told us. But under ordinary circumstances, it wouldn’t be affected. In the demonstration for tube makers, du Pont people placed a lighted cigaret on a sheet of Mylar draped over a piece of plate glass, with no harmful effect, pointing out that heat is diffused by the glass. Melting or burning, they said, is much less of a hazard with Mylar than with the commonly used polystyrene external implosion plates. The whole question of scratch & burn, they said, “is something for tube & set makers to evaluate.” Costs: On one aspect of the cost picture, everyone is agreed — that there’s no way to know for sure until somebody tries production. However, du Pont claims that pro cessed laminated film in 23-in. size should cost tube maker about $1 per tube, vs. $1.85 for Corning glass cap. Since Mylar requires only a sliver of epoxy resin to bond it to tube, Du Pont says, there should be more savings over the l-to-1% lb. of resin per tube used in the Corning process. The company concedes, however, that processing, labor & equipment costs are unknown. Production & rebuilding: Using converted drape forming machinery, a tube maker can process one tube a minute per machine, du Pont engineers told us. Can the Mylar shield be removed from the tube ? Since the adhesive takes couple of days to “set” at room temperature, rejects can be easily reprocessed, they said. They weren’t certain whether the Mylar shield could be economically removed from used duds for rebuilding. How Shield is Applied to Tube Here’s how the Mylar shield is shaped & fixed to picture tube in a single operation: “Adhesive is applied to the edges of a clean picture tube which is then placed in the drape-forming machine, face up. The face of the tube is covered with a relatively thin epoxy adhesive. The Mylar film is clamped above the picture tube, heated, and then draped over the tube face with a combination of motion & vacuum in such a way that no air bubbles are trapped between the film & the glass. A metal band drawn tight around the film & tube holds the film in place until the adhesives harden. The tube is removed from the drape-former as soon as the excess film has been trimmed. It is held face up until the quick-setting epoxy adhesive hardens enough to stand pressure without deforming.” Du Pont hopes to arrange with manufacturers of vacuum-forming production machinery to run off more Mylar-shield tube samples. They declined to state where their current tube samples had been processed. One tube maker (not the one referred to on p. 16) expressed cautious interest after seeing du Pont presentation & demonstration. National Video Pres. Asher Cole told us he thought process has “possibilities.” He added: “We’re following this with great interest. We must learn more about it, but we can’t get cost answers until there’s some production experience. If we could save $l-to-$1.50 per-tube, it could be very valuable. It needs more developmental work.” “We’ve gotten to the point where we can get general industry opinions,” echoes du Pont Lab’s Jay J. Stewart. “Now we want to encourage the industry’s active participation in further development.” He said he believed Mylarshielded tubes can “comfortably be in production in 12 months.” Motorola’s new address is 9401 W. Grand Ave., Franklin Park, 111. (NAtional 5-6000). Obituary John Fisher, 55, vp-founder of the Astron Corp., died in the TWA-UAL jetliner collision Dec. 16. Others with electronics industry connections: Arthur Burten, 35, industrial sales mgr., Astron Corp.; Herman Mueller, 41, research chief, Liquidometer special products div.; Murray T. Wright, 30, GE missile-development presentation specialist (his father, Clark M. Wright, is sub-contracting mgr., Schenectady GE plant) ; Lester Mogren, 36, IBM products field engineer; David W. Plummer, 25, IBM systems technician; George Keenan, 32, GE installation & service dept, engineer; Stephen Baltz, 11, son of William S. Baltz, vp & chief legal counsel. Admiral.