Re: 465 Display Help Needed


Stan or Patricia Griffiths <w7ni@...>
 

CRT Mesh comment below:

dhuster@pb.k12.mo.us wrote:

A few comments on what has been offered so far.

The characteristic fuzziness of a 465/475 and 7K scopes over their
earlier cousins (and which apparently is NOT your problem since you
describe major "focus" problems) is due to the inclusion of a scan
expansion mesh within the jug through which the electron beam has to
pass, causing a small amount of beam scatter. The mesh is there to
improve geometry.
My understanding of the reason an expansion mesh was used in 465 and later
vintage tubes was really to improve the vertical and horizontal sensitivity
of the CRT such that expensive transistors would no longer be necessary in
the vertical and horizontal scope amplifiers. It was mostly a manufacturing
cost reduction measure with a spot size tradeoff. Not a good tradeoff, in my
opinion.

Compare the output stages of the 547, 453, and 454 scopes to what you see in
the 465 and 475 and you will see what I am talking about.

Stan
w7ni@easystreet.com

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