[NJARC] Re: NJARC Digest, Vol 32, Issue 6

[Nick Senker]

As in my previous reply, this is all covered at http://home.pacbell.net/philbert/tuning_eye/tun_eye.htm
Thanks, Nick

-----Original Message-----
>From: Derm Whelan <dermwhelan at yahoo.com>
>Sent: Dec 8, 2006 5:00 AM
>To: njarc at mailman.qth.net
>Subject: [NJARC] Re: NJARC Digest, Vol 32, Issue 6
>
>Visit our web site - See http://www.njarc.org
>_______________________________________________
>Hello again,
>   
>  Here is another article from SCARS. 
>   
>  There are some 1930's 40"s articles I rememebr from the literature but which are not on the net. When I return to Newfoindland next week I will try to find them and post them up. But I am quite certain the results will not contradict Ludwell's findings.
>   
>  Best from Crotia.
>   
>  Derm Whelan
>   
>  Tuning Eye Tube Rejuvenation
>    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.
>  Several rejuvenation methods have been suggested but I’ve yet to find one that works successfully. 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. Rejuvenation experiments conducted by Ludwell Sibley have involved heating the target using microwaves or magnetic fields. The results have been disappointing. Since lasers have revolutionized just about everything from medicine to peeling paint - perhaps someone will develop a laser rejuvenation process.
>  The 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.
>   
>   
>
>
>
>As always,
>
> 
>
>Derm Whelan
>
> 
>
>
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