HP9836C colour alignment (grey scale tracking)

Tony Duell ard at p850ug1.demon.co.uk
Mon Sep 29 15:36:14 CDT 2008

Incidentally, in another thread you described the method of setting the 
purite on a delta-gun CRT by using both ring magnets on the back of the 
yoke and moving the yoke longtitudinally on the CRT neck. 

It's been a long time since I did this, but yes, you're right, the Barco 
manual I've been looking in describes just that procedure. And I think I 
understand how it works

When the CRT is made, the shadowmask and phosphor postions determine the 
'deflection centres' of each beam. In fact I've read somewhere that the 
phosphor dots were created by coating the inside of the faceplate 
unformly with a given colour of phosphor and a resist, putting the 
shadowmask in place and then using a point sourcce of (UV?) light at the 
appropriate defleciton centre position to cure the resist of thoat colour 
phosphor dots (shining thogu hte shadowmask holes, of course), after 
which the remaining unwanted phosphor was washed off.

Anyway, back to the purity adjustmets. Basically (and there is some 
interaction), the rign magnets get the electron beams to pass through 
those deflection centre ppints, moving the yoke gets the actual 
deflecitons centres produced by that yoke to align with the ones used to 
position the phosphors.


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