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Service Manual
5.
Repeat for blue focus VR while projecting blue
only.
6.
Repeat for green.
Focus - Optical Lens Adjustment
Optical Adjustments
Note: This adjustment normally should not require
resetting unless the lens has been replaced or
adjustment has changed.
1.
Optical focus adjustment is located on the top of
each CRT lens system. Loosen the adjustment
knurled locking knob. (Figure 25)
Figure 25. Optical Lens focus Adjustment
2.
Turn the PTV ON. Apply and view a monoscope
pattern.
3.
Adjust each lens focus for best focus while viewing
each CRT.
4.
Cover the red and blue CRT, projecting green only.
Rotate the green lens for best focus around screen
center area.
5.
Do the same for the red focus lens while projecting
red only.
6.
Repeat for blue.
Electric & VM Focus Adjustment,
Complete adjustment
(Perform this adjustment when a CRT is replaced
or when major adjustment is required)
Preparation:
1.
NTSC monoscope pattern.
2.
NTSC cross hatch pattern with dots (pincushion).
3.
Set DAC D0f from 0 to 1 (disabling digital
convergence.)
4.
Position the longer tab of the four-pole magnet to
90 degrees (uncorrected position). (See
Figure 27).
5.
Position the long tab of all alignment magnets and
of the dummy ring together in an uncorrected
position. (See Figure 28).
Procedure:
1.
Apply an NTSC cross hatch pattern with dots.
2.
Assure that digital convergence is disabled (Dac
D0F from 0 to 1).
3.
Project red only. (Cover green and blue CRTs.)
4.
Turn the red electrical focus adjustment VR (on
focus pack) fully counterclockwise and note the
position of the dots at the center of the picture.
5.
Turn the red electrical focus adjustment VR
fully clockwise.
6.
If the position of the dots at the center of the screen
moves from the position noted in step 4., adjust the
four pole magnets until the dots are in the same
position as noted in step4.
7.
Turn the red electrical focus adjustment VR (on
focus pack) fully counterclockwise and confirm that
the position of the dots at the center of the screen
did not move from their position noted in ste p6.
8.
If the position of the dots at the center of screen
moved, repeat from step 4.
B G R
Adjustment knurled
locking knobs
REAR VIEW
Figure 26. VM Coil with focus
correction magnet
6-pole magnet
4-pole magnet
Alignment magnet
(Dummy
ring)
Figure 27. 4-pole magnet
Set 90 degrees
Figure 28. Alignment magnet
(or dummy ring)
