[NJARC] Dim eye tubes

[Jim Whartenby]

Greetings Nick
I don't know the exact cause.  The phosphor coating either wears out,
wears off or get contaminated by the electrons bombarding it.  The same
thing appears to happen to CRTs.

I visited a TV shop in Bound Brook, NJ to pick up a donation of vacuum
tubes for the club at least 8 or so years ago.  In talking with the
owner, he mentioned that he had noticed that this problem happened to a
TV CRT he used to align video camcorders.

He had adjusted a TV so that the top portion of the CRT displayed the
sync bar and never changed the settings. It stayed this way for years. 
When he needed the set for another type of test, he readjusted the
controls and noticed that the area that had been black, that is not
exposed to the electron beam, showed much brighter colors then the rest
of the screen.  So it appears that the phosphors don't last forever.

Lud Sibley experimented with trying to rejuvenate eye tubes with no
success.   He even put a tube or two in the microwave oven!  Nice
sparks but no joy.
Regards,
Jim

--- Nick Senker <ns539 at earthlink.net> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Why do eye tubes (eg 6U5, 6E5, etc) lose their brightness?  Is it a
> failure of the phosphor coating?  I checked one that had good
> emmision, yet it was very dim. Nick Senker
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