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Discussion Starter #1
Check the lower left side of the attachment for a reason that worn tubes have bad gamma responce. From a Sencore User Manual. Oh yeah, people that write in books oughta be switched.

 

sencore.pdf 98.3740234375k . file
 

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Very good article tse . I've read this before but it is a very good refresher on the inner workings of a CRT . :)
 

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What year was this document published? Seems a bit dated to me and does not mention the type of cathode it is referring to. This is very important becasue most modern CRTs use dispensor cathodes which I do not think would exhibit the issues mentioned.
 

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I hope I'm not posting bad info. There is no date in the booklet that I can find. The equipment was recently purchased.
 

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My CR7000 book has the same info. And I HAVE been able to get out some H-K shorts.


It's somewhat dated, but keep in mind that the CR7000 is used to rejuvenate somewhat dated tubes. Our CRT's would fall into that category, so the info applies.


Marc
 

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Quote:
Originally Posted by Tinman
My CR7000 book has the same info. And I HAVE been able to get out some H-K shorts.


It's somewhat dated, but keep in mind that the CR7000 is used to rejuvenate somewhat dated tubes. Our CRT's would fall into that category, so the info applies.


Marc
This information is true only if the CRT is using an oxide cathode, it does not apply with a dispensor cathode. To "rejuvanate" an oxide cathode it appears that the CR7000 just applies more current to the cathode in order to burn off the oxide layer that is formed after many hours of operation. Certainly shorts that are caused by a contaniment may be fixed by blowing it off with a HV pulse but this only works sometimes.
 

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Discussion Starter #7
The part that I liked was where bad gamma response was explained by the low drive electrons coming from a small part of the cathode where the coating would wear sooner than the area that the higher drive level electrons would come from. This caused low emission during dark scene content. May not be applicable with the different types of cathodes.
 
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