[NJARC] Dim eye tubes

[Nick Senker]

It seems CRTs used in monitors and TVs are not quite the same as eye tubes.  CRT pix tubes have focused high energy electron guns that can easily burn the phosphors.  I recall working on an old B/W TV where a spot in the center of the screen had completely burned a hole in the phosphor coating.  I'm not an EE but it seems the eye tube emmision is more diffuse and much lower energy.  I appreciate everyones comments.  Nick

-----Original Message-----
>From: michael s christiansen <kb2vrm at juno.com>
>Sent: Dec 6, 2006 11:21 PM
>To: njarc at mailman.qth.net
>Subject: Re: [NJARC] Dim eye tubes
>
>Visit our web site - See http://www.njarc.org
>_______________________________________________
>Hi guys, That's why they have screen savers on computers. I've seen old
>monitors with text actually burned into the CRT. And now on to something
>completely different, Girl Scout Cookies will be delivered the night of
>the party to those folks who purchased them at the last clinic   Thanks,
>Mike Christiansen
>On Wed, 6 Dec 2006 15:51:54 -0800 (PST) Jim Whartenby
><antqradio at sbcglobal.net> writes:
>> Visit our web site - See http://www.njarc.org
>> _______________________________________________
>> 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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>> > 
>> 
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