Westinghouse K840CK15 Restoration

[Electronic M]

Originally Posted by etype2

Starting in June, 1955 with the introduction of the RCA CTC-4 the WCG of the 15GP22 and 21CT55 were changed to less saturated colors according to comments read in this forum.

* Added by author.

15GP22 used in our restored Westinghouse H840CK15.

Something to note: the CTC-4 didn't reduce color gamut. It reduced chroma video bandwidth. Bandwidth reduction reduces the amount of color detail (ie a CTC2 would color smaller dots of a fireworks display than a CTC-4 could), but doesn't affect the color gamut. The color gamut is affected by the phosphors and the signal matrixing equations in the TV. The CTC-4 used a 21AXP22 and some of those sets have the early AXPs that are said to have the correct NTSC phosphor. A CTC-4 may have less color detail and a redesigned demodulator circuit (to reduce parts count and make the set more affordable), but I have to believe RCA was still shooting for NTSC correct matrixing.

One thing to consider: 15GP22 based sets have a coarser phosphor dot pattern relative to screen size than 21AXP22 sets do so the to an extent the increased detail a CT-100s demodulator gives relative to a CTC-4 is atleast partially wasted in the CT-100 due to its coarse dot structure.
Probably the best set for seeing the full quality of early NTSC would be a 21CT55 or a CBS 205 which had the wideband chroma, fine phosphor dot pitch and NTSC phosphored CRTs.