Sharp 20GT-15, Service Manual

Page: 10 / 40

20GT-15
8
PURITY ADJUSTMENT
ADJUSTMENT POINT
ADJUSTMENT CONDITION / PROCEDURE
WAVEFORM OR OTHERS
1
NO
PURITY ADJ.
(1)
Receive the GREEN -ONLY signal. Adjust the beam current to ~700
µ
A (21"&20")/
~500
µ
A(14").
(2)
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. 1-1 through the microscope. Adjust the landings to A rank requirement.
(4)
Orient the raster rotation to 0 eastward.
(5)
Tighten up the deflection coil screws. Tightening torque : 108N
±
20N (11Kgf
±
2Kgf)
(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
µ
A.
(For 14", the beam current should be over 500
µ
A).
Fig. 1-1
Fig. 1-2 Rank A (On the right of CRT)
Fig. 1-3 Rank A (On the left of CRT)
a
A
A=B
B
A
A=B
B
b
CONVERGENCE ADJUSTMENT
ADJUSTMENT POINT
ADJUSTMENT CONDITION / PROCEDURE
WAVEFORM OR OTHERS
1
NO
CONVERGENC ADJ (To be done after the purity adjustment.
(1)
Receive the "Crosshatch Pattern" signal.
(2)
Using the remote controller, call NORMAL mode.
(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. a : Drive the wedge at point " a " and swing the deflection coil upward.
b)
Fig. b : Drive the wedge at point " b " and " c " and swing the deflection coil downward.
c)
Fig. c : Drive the " c " wedge deeper and swing the deflection coil rightward.
d)
Fig. d : 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.
Fig. a Fig. b Fig. c Fig. d
R G B
R G B
CRT NECK
Lacquer
Purity Magnet
4-Pole Magnet
6-Pole Magnet.
20cm
40cm (14") (21")
B G R
B G R
R G B
B G R
B G R
R G B
Wedge "a"
Wedge "b"
Wedge "c"
About 100 Deg
About 100 Deg
Lacquer