Westinghouse K840CK15 Restoration

[old_tv_nut]

A 15GP22 should produce exactly the same greens and cyans in either the CT100 or the Westy if the color demods/matrix circuits are correctly adjusted to NTSC specs.

A 15GP22 will not produce as deep violet-blue, purple, or saturated magenta as later tubes because the blue phosphor color is more toward cyan than the later sulfide blue.

However, in later sets, when the demodulator gains and angles were adjusted to get a good range of skin tones with the later phosphors, the rendition of purples and magentas was thrown under the bus because there are no well-recognized object "memory" colors in that range. So, even though the later tubes could produce more saturated magenta of the correct hue, the demodulators might not output the right signals to get it.

EDIT: then in the 70s, "auto color" came along, which essentially made sure any purplish or greenish skin hues were suppressed. In the simple circuits in most sets, this meant that only cyan and red-orange hues were normal strength, and green and magenta saturation was reduced greatly. The only exception was RCA, whose circuit only affected hues near red-orange (skin), and left strong greens and magentas alone.