HP9836C colour alignment (grey scale tracking)

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.