Here’s how to adjust the astig magnets:
Bring the two tabs of each pair of 2, 4 and 6 pole magnets so that they
overlap each other. The tabs should now be in the neutral position, and rotating
the tabs around the neck of the tube should have no or minimal effect on the
dots or flares that you see. Note that there are usually two sets of tabs
exactly 180 degrees apart. If you overlap opposing tabs, rotating the pair
around the tube will greatly affect the astig, so rotate only one tab 180
degrees around the neck so that the two matching tabs are on top of one another.
Once you have confirmed that the right pair of tabs are overlapping, you
start to move the 2 pole pair of tabs apart slightly. You’ll see that the flare
around the dots will start to rotate, and there should be a point where careful
positioning of the 2 pole tabs will result in a good round looking dot.
To complicate matters, you want to then ramp up and down the electronic
focusing control via the remote. As you electronically focus and defocus the
tube, you should remain at round dots that does not move on the screen. It will
take some readjustment of the 2 pole magnets so that the dots remain round and
so that the dots do not move as you ramp the electronic focus controls up and
down.
Next is the 4 pole magnet. As mentioned above, the 4 pole and 6 pole magnets
are more of a fine tuning for the 2 pole magnets. They will affect the astig and
roundness of the dots, and of course will interact somewhat with the 2 pole
magnets. A carefully step by step adjustment of the 2 pole and 4 pole magnets
along with ramping the focus up and down will result in great astigmatism on
each tube.
One way to adjust the astig with better results is to look directly into the
lens to the tube surface with sunglasses on. Your eyes are now a lot closer to
the tube face, and you don’t need to squint in the darkness to see exactly
whether the dots are round on the screen that’s across the room.
Three more images below show good and bad astigmatism but with the internal H
focusing pattern in the NEC PG sets.
The image below shows good astigmatism, good focus. Both the H and V lines
that make up the H pattern are crisp:
|
