Toshiba M-V19H01, Service Manual

Page: 126 / 166

Alignment and Adjustments (Electrical)
6-6
6-2-5 CRT Gray Scale Adjustment
1. Set the Color control to minimum.
2. Adjust the Brightness and Contrast controls
for a low light area.
3. Adjust the Red, Green and Blue Bias controls
to obtain a gray raster of low brightness.
4. Adjust the Brightness and Contrast controls to
maximum.
5. Adjust the Blue Drive and Red Drive controls
for a properly white-balanced picture in high
light areas.
6. Repeat steps 2 through 5 for correct gray
scale.
6-2-6 Automatic Degaussing
A degaussing coil is mounted around the
picture tube. External degaussing after
moving the TV should be unnecessary, but the
receiver must be properly degaussed upon
installation.
The degaussing coil operates for about 1
second after the power is switched ON. If the
set is moved or turned in a different direction,
the power should be OFF for at least 10
minutes.
If the chassis or parts of the cabinet become
magnetized, poor color purity will result; if
this condition occurs, use an external
degaussing coil. Slowly move the degaussing
coil all around receiver, including its faceplate,
picture tube, sides and front. Slowly
withdraw the coil to a distance of about 6 feet
before turning the TV OFF or disconnecting it
from the AC source.
If color shading still persists, do the following
Color Purity and Convergence adjustments.
6-2-7 Color Purity Adjustment
1. If a magnetic-tape beam bender is mounted on
the neck of the picture tube, replace it with an
adjustable-type (Magnet Assembly) prior to
center-purity and center-convergence
adjustments. Consult the replacement parts
list for the correct part number.
2. Warm up the MVCR for 20 minutes, with
Brightness set to maximum.
3. Fully degauss the receiver. Use an external
degaussing coil.
4. Roughly adjust convergence.
5. Input a black and white signal.
6. Turn the low-light controls (Red and Blue)
fully counterclockwise to obtain a green field.
Adjust the Drive controls for a green field.
7. Loosen the Deflection Yoke clamp screw, and
move the Deflection Yoke as close to the
purity magnet as possible.
8. Loosen the purity magnet clamp. Adjust the
purity magnet to set a vertical green raster
precisely at the center of the screen. Then
tighten the clamp.
9. Slowly move the Deflection Yoke forward, and
adjust it for the best overall green screen.
10. Tighten the Deflection Yoke clamp screw.
11. Produce a blue and red raster. Turn the bias
controls fully clockwise. Ensure that good
purity is obtained on each field.