THE SET

tricolor history

Andy's interesting contribution sheds light on some mostly forgotten history of early television color picture tubes. Before RCA introduced the 21AXP22 late in 1954 as its first 21-in. tricolor picture tube, they had plans to introduce a 19-inch version of their production tricolor tube, the 15GP22. That 15-inch tube is compared to the 19-inch tube in the vintage graphic to the left.

The above scan of the 1962 GE picture tube manual correctly shows the RCA 15GP22 and CBS 15HP22 as 45-degree deflection angle designs, which resulted in the great overall length of these tubes for so small a picture. The 19TP22 (a photograph of this CRT has not yet surfaced) was a 60-degree design. Therefore, it is nearly two-inches shorter even though the screen is significantly larger. Note, also above, all three tubes use electrostatic convergence -- a practice quickly dropped, as it required extensive high-voltage circuitry to provide the modulated 10-kV convergence signal.

These were the last tubes to use a flange for the high-voltage connection. The metal-funnel of the 21AXP22 used a lip; finally, the all-glass 21CYP22 returned to the cavity connection used extensively on black and white picture tubes.
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Typical Operating Conditions, see table below, lists the same 20-pin base and pinout for all three electrostatic convergence tubes. Twenty-pin bases were needed to provide high-voltage isolation for the convergence signal pin. Six of the actual pins -- 10, 11, and 12, then 14 to 16 -- were not installed on these tubes, thus keeping pin 13 well away from the others.

Non-electrostatic convergence designs used a 14-pin base.

I found it interesting that the newer RCA 21AXP22 (lip) and older CBS 19VP22 (flange) used the same base and had the same pinout. There is a picture of the 19VP22 elsewhere on this site; it is easily located with the search engine at the beginning of Tidbits II.

[Updated 6-17-2002; 5-11-2004]

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