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 NEC PG Series
Mechanical Setup Procedure
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(Page 7)
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ASTIGMATISM (CPC) MAGNETS
If the above focus test indicated that you need to do the astig adjustment,
proceed with this section.
Lower the projector brightness and increase the contrast. This will help you see
the dot pattern in
this step. Now put up the coarse dot pattern with only the green CRT on and
completely defocus the
green tube with the focus pot. You should see big round blobs on the screen.
Usually, these blobs
will be misshapen, which is why you are doing this step. This is due to the
astig adjustments being
off. Rotate the astig magnets to make the dots in the CENTER of the screen as
round as possible.
You will notice that one pair of magnets moves the dot around and the other
magnet pair changes
their shape.
NOTE: when you do any adjustment inside the projector only use one hand to make
the adjustment
and don't touch a metal ground with the other hand. If you want to feel safer
try wearing a tight
fitting rubber glove on the hand you are using to make adjustments with.
You are adjusting the magnet positions to get the dot to the center of the halo
(or circular blur) and
the halo itself a nice round shape. Once you think everything looks uniform, in
the CENTER of the
screen, try focusing the green with the focus pot. Put up the crosshair and see
if it moved. Use the
centering magnets to once again line up the crosshair in the middle of the
screen (align it with the
center of the string).
As stated above the astig and centering magnet adjustments affect each other.
I.E., make one
adjustment and the other goes out of adjustment. So you will have to work back
and forth between
the centering and astig adjustments to keep the crosshair pattern centered on
your string and the
dots nice and round. This may take a few attempts. Once you have that complete,
run the focus pot
back and forth with the crosshair pattern displayed. If the crosshair does NOT
move, you got it the
first time! If it moves at all, in any direction, you must work on the
astigmatism magnets again.
When you adjust the focus pot the crosshair should blur evenly and not to just
one side. This is
basically a matter of making ever smaller adjustments until you get it right.
This is the single most
important adjustment on the NEC, so take your time. You DID brew that coffee,
right?
Don't forget to focus it with the focus pot, while the focus menu is set to “0”.
This gives you the
proper center for making electronic adjustments later if needed. Once the green
tube is centered and
focused, it is now the reference for everything else.
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