There is no failure in a color CRT that can produce a black & white image. All color CRT's utilize 3 separate electron emitters (for red, green, and blue) that are driven separately by the decoding electronics. Even total failure of the blue gun, for example, would produce a yellow image (since it's an additive color process, and red and green are left).

A failure in the color subcarrier detection circuitry could produce a black & white image. I hope you're happy you asked. Nobody cares about old analog electronics any more.

I just noticed you said all the overhead monitors had the same problem. That means the problem was in the playback device (probably a "Hi-8" player. All small-format analog videotape players use a "color-under" system wherein the color information is modulated onto a subcarrier much lower in frequency than the standard NTSC subcarrier of 3.579545 MHz. Any number of problems in detecting and converting the recorded color information can result in a black & white picture.


[This message has been edited by RichG (edited Jan 03, 2004).]