[NJARC] Dim eye tubes - How to make them brighter...

[Nick Senker]

This is covered in the link I just posted ( http://home.pacbell.net/philbert/tuning_eye/tun_eye.htm )
Thanks, Nick

-----Original Message-----
>From: Thomas Lee <thomas_v_lee at hotmail.com>
>Sent: Dec 8, 2006 1:18 AM
>To: njarc at mailman.qth.net
>Subject: [NJARC] Dim eye tubes - How to make them brighter...
>
>Visit our web site - See http://www.njarc.org
>_______________________________________________
>Thought this might be of interest...  Taken from a link now long 
>forgotten...
>
>One method that can brighten a dim electron-ray tube is to increase the 
>voltage applied to the fluorescent target. Small changes in supply voltage 
>produce disproportionately larger luminance changes. As a last-ditch effort 
>in some sets, especially where the very expensive 6T5 is involved, the 
>target could be rewired directly to the rectifier cathode to boost B+ by as 
>much as 100 volts. This method is influenced by a number of factors in 
>receiver design and operation however and may not work in every set.
>
>One published method described using a technique similar to that applied to 
>rejuvenate cathode-ray tubes. The problem however is not emission, which 
>this method addresses, but target contamination. CRT rejuvenation techniques 
>have no influence on the condition of phosphors.
>
>Electron-ray tubes remain bright for about a thousand hours of operation. 
>The heaters in electron-ray tubes can fail or weaken before the targets 
>become dim, but this is not the norm. Target dimness is believed to be due 
>to physical or chemical contamination of the willemite boundary layer by 
>Barium and other ions that are boiled off through normal cathode emission. 
>This contamination is visible as streaks of darker gray discoloration to the 
>otherwise light gray coat of a new electron-ray tube target. If you?re 
>rummaging through a box full of tubes at a flea market and spot a tuning eye 
>tube, look for this discoloration before you buy. Be certain to examine the 
>target surface in a bright light. The target of a good - or reasonably good 
>- tube will have a consistent light gray tone. Look for two thin lighter 
>gray streaks that are in the same line but opposite one another. These light 
>streaks are produced by the shadow cast by light shield?s supporting pins 
>and are evidence of a well-used tube.
>
>
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