LG RU-27FB30C Series Service Manual page 37

PRELIMINARY SETUP
1. Allow the receiver to warm up for 15 to 20 minutes.
2. Degauss the CRT.
3. Connect a cross hatch generator to the receiver and
"rough in" the static (center) convergence. Follow
the Convergence Procedure.
4. Adjust for the focus.
PURITY ADJUSTMENT
1. Purity tab positioning. Set the 2 pole purity tabs
together in the 3 or 9 o'clock positions and the 4-
and 6-pole purity tabs together in the 12 or 6 o'clock
positions.
2. Move yoke to the maximum forward funnel position.
3. Next, switch the crosshatch generator to a red field.
4. Pull the yoke toward the rear of the CRT neck, keep
ing it centered, until a red raster is displayed.
5. If the red raster is not displayed as a pure red field,
adjusts the 2-pole purity tabs until a pure field is
obtained.
6. Check for proper yoke tilt setting.
Wedges' Adhesive Tape (3)
Deflection Yoke
Yoke's Glass Cloth Tape
Rubber Wedges (3)
3828VD0210A
SERVICING
PURITY & CONVERGENCE SETUP PROCEDURE
Purity & Convergence
Magnet Assembly Unit
6 Pole
Purity Magnet
4 Pole
3-5
CONVERGENCE ADJUSTMENT
1. Release locking assembly.
2. Connect crosshatch generator to the receiver and
adjust static (center) convergence as follows:
a. Adjust the 4-pole static control by moving the
two tabs separately to converge the red and
blue lines horizontally. Move the two tabs to
gether around the neck of the CRT (in a 45º
arc) from the top-dead-center position to con
verge the red and blue lines vertically.
b. After the 4-pole control has been adjusted to su
perimpose the red and blue lines on top of one
another. Use the 6-pole static adjustment to
place the converged red and blue lines over
the green line. Move the two tabs together
around the neck of the CRT (in a 30º arc) from
the top-dead-center posotion to move the lines
vertically. Adjusting the two tabs separately will
move the converged beam to the left or right.
Using a crosshatch generator capable of pro
ducing individual fields, adjust the generator
to produce a red field. Use the purity tabs to
center a red stripe.
CRT Ring Location Purity
Adjust Tabs Beam Movement
for Convergence
Ring Rotation direction
Pairs of Both Tabs
Opposite
6 Pole
Convergence
R&B over G
Same
Opposite
4 Pole
Convergence
R over B
Same
Movement of Red
and Blue Beams
B B
OR
R R
OR
B R
B R
B B
OR
R
R
OR
B R
R B
FCN - SERVICING