daver2
10k Member
Nice job!
Don't forget to test the IEEE488 port as well (when you get the keyboard working)...
Dave
Don't forget to test the IEEE488 port as well (when you get the keyboard working)...
Dave
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PET 4032 replacement CRT (9 inch)
- Thread starter gr8bit
- Start date
Hugo Holden
Veteran Member
The standard P4 phosphor, for white CRT's, is made of a mixture of fine granules, both the complimentary colors, blue & yellow (in the scenario of additive color mixing). The eye perceives this as white.
If you look at the CRT faceplate under high magnification you will see discrete blue & yellow granules with the phosphor illuminated. Interestingly, "pretend white" which our visual system synthesizes as white, from a mix of blue & yellow (which should really have been a mix of R ,G & B phosphors as it is in a color CRT) is not the same as when we are fooled into seeing white from proportions of RG&B. Monochrome CRT's, for this reason, have a peculiar almost "moonlight" look to them. Other times it has been described as silver looking "on the silver screen".
Some particular manufacturer's mixes of the P4 phosphor had a preponderance of blue, others, especially one mix made by Dumont in the USA, had more yellow, that one tended to produced black and white images that looked like sepia tone photos.
Also, because the "white" is synthesized from only two wavelengenths (not a mix of RGB) a camera can be more respsonsibve to one of the colors, in particularly the shorter wavelength ones. Which explains why the photo looks like the text is blue, but your eye sees it as white.
If you look at the CRT faceplate under high magnification you will see discrete blue & yellow granules with the phosphor illuminated. Interestingly, "pretend white" which our visual system synthesizes as white, from a mix of blue & yellow (which should really have been a mix of R ,G & B phosphors as it is in a color CRT) is not the same as when we are fooled into seeing white from proportions of RG&B. Monochrome CRT's, for this reason, have a peculiar almost "moonlight" look to them. Other times it has been described as silver looking "on the silver screen".
Some particular manufacturer's mixes of the P4 phosphor had a preponderance of blue, others, especially one mix made by Dumont in the USA, had more yellow, that one tended to produced black and white images that looked like sepia tone photos.
Also, because the "white" is synthesized from only two wavelengenths (not a mix of RGB) a camera can be more respsonsibve to one of the colors, in particularly the shorter wavelength ones. Which explains why the photo looks like the text is blue, but your eye sees it as white.