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Guys- Dug out that book- "The Cathode Ray Tube" & looked up what it said about that 30" Dumont CRT-"....For many years Du Mont held the size recordw/their 30"round metal 30BP4 of 1950 to '51, which was used in their Royal Sovereign deluxe television console. (It) used 90-degree deflection to keep the length within reason & employed magnetic focusing. Du Mont soon encountered cathode life problems because getters could be used only in the neck due to the unaluminised screen. Any getters used in the forward portion of the tube would leave barium patches on the phosphor, resulting in non- uniform brightness across the screen. Neck mounted getters were inadequate to maintain a good vacuum w/the large volume & internal surface area of such a large picture tube. A last time build of 500 tubes was made for replacement purposes & the 30BP4 was discontinued after only 1 to 2 years of production. A conversion kit to allow replacement w/a 27" rectangular glass picture tube was also produced to allow future replacements to be made." So there you have it- if anybody runs across one of these bad boys, you'll know the story of it. -Sandy G.
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02-24-2004, 07:29 AM
Linear Mode
