Lear Siegler ADM-3A CRT problem

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Fri May 28 00:26:02 2004

> [...] Lear Siegler ADM 3A [...]

> When I originally stored it (about 4 years ago), all was well. But
> now there are bunch of "spots" peppering the outer perimeter of the
> front of the CRT. These spots are NOT on the surface of the CRT
> (i.e., it is not a "bubbling" sort of phenomenon), but rather behind
> the outer glass.

Based on the picture, I would guess this is the problem that's been
discussed on-list in the past, where something glued to the front of
the CRT develops problems. But that's just a guess, and a rather
uninformed one at that; I'll let those who actually know the problem
speak to that.

> 1) What's happened to my CRT? Is this symptomatic of a slow air
> leak?

No; that is so unlikely that I wouldn't even consider it, and it
doesn't fit the symptoms anyway. The vacuum inside a CRT has to be a
pretty hard vacuum, and even the slowest ordinary leak will completely
ruin it in no time flat. In principle it may be possible to have a
leak slow enough that it still mostly works after some years - but it
wouldn't affect some areas of the screen and not others; gas in the
tube will affect the whole screen, because it will interfere with
electron flight everywhere.

> 2) Can the CRT be fixed/repaired? (my guess is no)

If it's the problem I refer to above, it can be fixed, but it's not
trivial. Again, I'll let people familiar with the problem speak, if
they think it might be what's wrong with your 3A.

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Received on Fri May 28 2004 - 00:26:02 BST