Quote:
Originally Posted by radio nut
. . . the crt is weak and has the classic "indian" test pattern burned onto the screen. . . . .
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Sheesh! I don't think I've ever seen test pattern burns except on TV station monitors, and no TV station would use a Muntz!
(Well, I once worked at a TV station that had Crosley monitors in the Lobby, but WLW-A, now WXIA, was owned by AVCO at the time, and boy, did they go away the moment the station was sold.)
On the conductive coating, a more logical guess is that someone cleaned off the old flaking paint not realizing that it was part of the tube.
However, I've seen a few rebuilt CRTs that had an external conductive coating where one was not specified (and if they do, you must fabricate a ground or it will bite you) and much more commonly, a new-out-of-the-box rebuilt CRT that was missing the coating.
A peculiarity of the CRT that you have is both the 16RP4 and 16RP4A require an ion trap while the 16RP4B does not! Back in the late 50's I replaced a CRT, I can't remember the tube number, but it was an all glass B&W roundie, where this tripped me up, and the rebuilt tube actually looked dimmer than the one it replaced until my boss removed the old ion trap that I had transferred to the new CRT! I felt like an idiot for not catching this, and he never let me forget it. I noticed the ion trap never had a brightest spot, even if reversed, and that should have been a clue, but I slept through it.
James