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In Reply to: Does Anyone Know What Produces the Brown Stains Inside Some Tubes Like the 845 (NT)? posted by GKwei on September 27, 2004 at 17:00:07:
They're caused by X-rays. That's why you don't see that type of discoloration on tubes that run at lower voltages, they don't
produce X-rays. This effect is useful as on glass tubes that
have no getter, like 4-400, 3-500, etc, it gives a rough
visual indication of the amount of use the tube has had.
Follow Ups:
I don't know, I have a few used X-ray tubes and the discolouration( while quite shaprly bounded ) is not brown, it's violet, and I have a few tubes which are definately not high voltage tubes with this sort of marking as well.It takes more than a few kV to make x-rays, even the statistical probability would give no significant output at even 845 voltages I think.
regard,
Douglas
!
Beware the man who behaves deceitfully towards others, for there is nothing else to save you from his deceiving you
it seems that the "brown" color developes in a heat dependent way. I have noticed some strange things with 83's as they will actually cause tubes located near them to show weird effects (violet glow in glass). But my experience with these tubes is limited to a single amp.
this X-ray valve is about a foot and a half long. big copper electrode with an angled tip and a Tungsten target( which is chewed all the hell up by HV electrons ) and a spherical sction about 8-inches in dia. with about half of it on the angled side of the electrode turned violet. the end near the filament is darker, but like an old 866...
regards,
Douglas
Beware the man who behaves deceitfully towards others, for there is nothing else to save you from his deceiving you
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