Hi:
I've posted photos showing darkening that I've described in previous
posts:
Photos are located in "Photos|figureloop": Member: figureloop
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Care to speculate on the cause of these different types of darkening?
And if this is possible to occur on new in box tubes, then why are some
tubes completely free of darkening? Note that I see insulating spacer
darkening on all other NIB tubes I've bought from non-Ebay sellers as
well. NL840s from Sphere show spacer darkening as well as "bleaching"
of the anode back wall, and ZM1040/Z566M from Ask Jan First show
darkening on the spacers.
I am not insinuating that these sellers have misrepresented their
products. I suspect that some sputtering of spacers may occur in
factory burn in procedures. Also, if there was an induction heating
step prior to filling that heated the elements to glowing heat, then it
is possible that this procedure causes darkening of spacers, and
possibly even emits metal vapors which condense on the walls of the
IN-18 tubes.
However, in the latter case, this would seem to indicate a great deal of
inconsistency in Russian IN-18 factories since clearly there are tubes
which show no darkening whatsoever. The darkening mystery continues...
