Sony KV-28FQ75U, Service Manual

Page: 21 / 108

21
•
When complete readjustment is necessary or a new picture tube is
installed, carry out the following adjustments.
•
Unless there are specific instructions to the contrary, carry out
these adjustments with the rated power supply.
•
Unless there are specific instructions to the contrary, set the
controls and switches to the following settings :
Contrast .................................. normal
Brightness .................................. normal
Preparation :
1. In order to reduce the influence of geomagnetism on the set’s
picture tube, face it in an easterly or westerly direction.
2. Switch on the TV set’s power and degauss with a degausser.
(1) Adjustment of Neck Assembly and Y-Splitting Axis.
1. Position the neck assembly as indicated in Fig.3-2.
2. Loosen the deflection yoke fixing screw.
6. Position the Y-splitting axis correction magnets located on the neck
assembly as indicated in Fig 3-1.
Carry out the adjustments in the following order :
3-1. Beam Landing.
3-2. Convergence.
3-3. Focus.
3-4. White Balance.
Note : Test equipment required.
1.
Color bar/pattern generator.
2. Degausser.
3. Oscilloscope.
4. Digital multimeter.
4. Move the deflection yoke backwards and adjust with the purity
magnet so that the red is at the centre and it aligns
symmetrically [See Fig.3-6].
5. Move the deflection yoke forward to the point where the entire
screen just becomes red [Mark its position].
6. Move the deflection yoke further forward until the screen just
changes colour at the edges. [Mark its position]
7. Position the deflection yoke between the two marks indicated
above.
8. Input a crosshatch pattern from the pattern generator and rotate the
deflection yoke so that the horizontal lines are parallel with the top
and bottom of the screen.
9. When the position of the deflection yoke has been determined,
fasten it with its fixing screw.
10. Adjust the upper and lower pin symmetrically by tilting the DY
up and down then insert a DY wedge at the top. Use the Y- splitting
axis magnets to finely adjust the pin balance. [Fig.3-3].
11. Adjust the H-trap by moving the DY left or right. Insert DY
wedges at top and bottom left and top and bottom right. Finely
adjust using the H-trap VR on the DY assembly. [See Fig.3-4].
12. Switch the pattern generator to green then blue and confirm the
purity.
13. If the beam does not land correctly in all the corners of the screen,
use disk magnets to correct it. [Confirm the corner landing for
green and blue]
SECTION 3
SET-UP ADJUSTMENTS
3-1. Beam Landing
Caution :
High voltages are present on the Deflection yoke terminals - take care
when handling the Deflection yoke whilst carrying out adjustments.
Fig.3-3
Fig.3-2 Neck assy
Align the edge
of the neck assy with
the edge of the G2 grid
on the G3 side.
G2
G1
G3
+
Fig.3-1
Y-splitting axis correction magnet
(2) Landing
Note : Before carrying out the following adjustments adjust the
magnets as indicated below [See Fig.3-5].
1. Input a crosshatch signal from the signal generator.
2. Rough-adjust the focus and horizontal convergence.
3. Switch from the crosshatch pattern to an all-red pattern.