Quote:
Originally Posted by cbenham
Re: the 931A being sensitive to fluorescent room light.
The early B&K Analyst flying spot scanner CRT produces lots of blue light and a good amount of ultraviolet as well. The 931A is the photomultiplier tube used in these old B&Ks
because it is most sensitive to blue light.
The B&K was running full tilt to produce the B&W TV test pattern image and even after many years the test signal is still quite contrasty and visually noise free.
Just trying to reconcile the "damage from room light" and the use of the 931A in the B&K Analyst that continues to work well even now.
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The optics were quite different - the video player used the blue/UV phosphor too, but had small lenses to focus the raster on an area of microfilm less than 3 mm x 4 mm, so the 931A may have been running at higher gain. Don't really know.