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Old 06-22-2011, 08:45 PM
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Steve McVoy Steve McVoy is offline
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Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 1,139
John, your supposition that the 3 bolt version is the earliest one conflicts with the information that Dave gave me some time ago. Here is what he wrote:

This tube [the 6 bolt version] was use in the tri-color models 1 and 2 and possibly the 2A. Model 1 was the first RCA demo to the FCC. These tubes were circa April, 1950 to February, 1952. Models 3 and 3A used a 3-bolt version. Starting with the 3, they improved the trajectory of the guide bolts for the shadow mask alignment. The model 4 appears to be the first of the glass tubes. Most of what I know can be found in the RCA Color TV submission to the FCC...the "red book"...and in the second "Proceedings of the IRE" on color television.
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