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Old 22nd Oct 2021, 8:49 am   #23
Join Date: Aug 2008
Location: Melbourne, Australia
Posts: 183
Default Re: 5FP7 project starting with the focusing coil.

Originally Posted by AdrianH View Post
Just wondering about adding an iron wire wrap over the focusing coil, does anyone know if it makes an improvement in that it may need less current through the coil?
Was thinking of two layers of 1.2mm, would it have any adverse effect?

Cleaned up an old Radar frame and started to mount parts in it to save all the mess.
Attachment 243929

Looking good Adrian

Yes the Focus coil was always a problem to me in 1990 mainly didn't want to wind a new coil or add to what i had .
You would think a round permanent magnet would be a easier fix .

Magnetic Focus
In early television tubes and in some high quality tubes such as tubes for film scanning, the focus lens takes the form of an electro-magnet or permanent magnet producing, over a short region, a magnetic field parallel to the axis of the tube. This magnetic field acts to bend the electron paths towards the axis and by correctly adjusting the strength of the field, the point of focus may be made to occur at the fluorescent screen

Iron wire sounds like it would help i would try it .
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