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Discussion Starter #1
J have just read trough the installation manual for the Sony G70 to see if I can do a calibration myself.

According to the installation manual there exist a special cap that should be put on the lens while adjusting the magnetic focus (AQP/DQP).

I'm just in the process of buying an used G70 and I'm not sure if this cap is still with the projector.

Can the magnetic focus be adjusted without this cap and/or how vital is it for getting a good picture ?


Thanks,

H-B
 

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The cap isn't by any means magical. It is merely one with a hole about 3 cm diameter in the center. This greatly reduces the f number of the lens and reduces the amount of confusion between blurring due to poor optical focus vs poor electromagnetic focus and astigmation. If optical focus is well done, you really don't need the cap. You normally should go back and forth between optical and beam focus any way to get both perfected. A quick way to get optical in quickly is to intentionally defocus the electron beam and display a field pattern. The adjust optical focus for one gun at a time to make the crystalline structure of the phosphor surface appear sharply on the screen. That works even when beam focus is way off because the phosphor crystalline structure is a physically constant and present feature of the surface you are trying to project. If you really want to replicate the effect of the hole cap, just take a piece of black kraft paper and cut out a hole. Tape the paper with a hole over the lense and you'll duplicate the effect of the cap. The presence or lack of the special cap should have no bearing on purchasing the projector.
 

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Discussion Starter #3
Thanks Guy,


I haven't calibrated a CRT before and when reading the manual thought it seemed pretty straightforward to do it yourself. Maybe a lot of work but not to difficult. Then I got uncertain when the special cap was mentioned.


I now feel relieved and will go ahead with my purchase and my step into the CRT world :)


/H-B
 

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Welcome to the CRT world. I assure you that you will get frustrated and daunted along the way, but the eventual destination is worth the path. The Sony's are pretty easy to set up and get a decent picture. It will take you several months of practice before you really begin perfecting the image. CRT setup is a skill which you improve each time you REDO it. For me, it's an almost meditative process. A full blown setup to maximize a projector's performance can take me 12 to 24 hours of work not counting hanging the projector, but you can get an emminently watchable image with a lot less time than that. It is a great help if another enthusiast in the area can help you out the first time.
 

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Guy is right, the cap is not neccessary. In fact I was told by William don't use it, just throw it away. He helped me through my set up of my G70.

John
 
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