Sharp 20U250 Service-Handbuch - Seite 8
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PURITY ADJUSTMENT
NO. Adjustment part
Adjusting procedure and conditions
1
PURITY ADJ.
1. Receive the GREEN-ONLY signal. Adjust the
beam current to about 700 mA.
2. Degauss the CRT. Maintain the purity magnet
at the zero magnetic field and keep the static
convergence roughly adjusted.
3. Observe the points a, b as shown in Fig. 4-1
through the microscope. Adjust the landing to
the rank A requirements.
4. Orient the raster rotation to 0 eastward.
5. Tighten up the deflection coil screws.
» Tightening torque: 108 ± 20 N (11 ±2 kgf)
6. Make sure the CRT corners landing meet the
A rank requirements. If not, stick the magnet
sheet to correct it.
Note: This adjustment must be done after
warming up the unit for 30 minutes
or longer with a beam current over
700 µA.
* For the following colours press R/C RGB key
to change.
Red-only
Green-only
Signal-colour
screen cleared
Waveform and others
a
b
Fig. 4-1
A
B
A = B
Fig. 4-2
Rank "A"
(on the right of the CRT)
Blue-only
A
B
A = B
Fig. 4-3
Rank "A"
(on the left of the CRT)
* Press R/C RGB key for a sec-
ond in NORMAL MODE, the
colour will change to RGB mono
colour mode.
8-1
CONVERGENCE ADJUSTMENT
NO. Adjustment part
Adjusting procedure and conditions
1
CONVERGENC
1. Receive the "Crosshatch Pattern" signal.
ADJ.
2. Using the remote controller, call NORMAL
(To be done
mode.
after the purity
adjustment.)
Static Convergence
1. Turn the 4-pole magnet to a proper opening
angle in order to superpose the blue and red
colours.
2. Turn the 6-pole magnet to a proper opening
angle in order to superpose the green colour
over the blue and red colours.
Dynamic Convergence
1. Adjust the convergence on the fringes of the
screen in the following steps.
a) Fig. 5-1: Drive the wedge at point "a" and
swing the deflection coil upward.
b) Fig. 5-2: Drive the wedge at points "b"
and "c", and swing the deflection coil
downward.
c) Fig. 5-3: Drive the "c" wedge deeper and
swing the deflection coil rightward.
d) Fig. 5-4: Drive the "b" wedge deeper and
swing the deflection coil leftward.
2. Fix all the wedges on the CRT and apply glass
tape over them.
3. Apply lacquer to the deflection yoke lock screw,
magnet unit (purity, 4-pole, 6-pole magnets)
and magnet unit lock screw.
Finally received the Red-only and Blue-only
signals to make sure there is no other colours
on the screen.
Waveform and others
BGR
B
G
R
Fig. 5-1
RGB
R
G
B
Fig. 5-2
RGB
B
G
R
Fig. 5-3
BGR
R
G
B
Fig. 5-4
Wedge "a"
About
About
100°
100°
Lacquer
Wedge
Wedge
"b"
"c"
Fig. 5-5
4-pole magnet
6-pole magnet
CRT neck
20mm
Lacquer
Purity magnet
Fig. 5-6
8-2