Service manual

SERVICING
3828VD0171G 3-3 DIGITAL FCS - SERVICING
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 genera-
tor to a red field.
4. Pull the yoke toward the rear of the
CRT neck, keeping it centered, until a
red raster is displayed.
5. If the red raster is not displayed
as a pure red field, adjust the 2-pole
purity tabs until a pure field is ob-
tained.
6. Check for proper yoke tilt setting.
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 con-
verge the red and blue lines horizon-
tally. Move the two tabs together around
the neck of the CRT (in a 45° arc) from
the top-dead center position to con-
verge the red and blue lines verti-
cally.
b. After the 4-pole control has been
adjusted to superimpose 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 30° arc) from the top-dead-center
position 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 producing individual fields,
adjust the generator to produce a red
field. Use the purity tabs to center a
red stripe.
VERTICAL-TILT WEDGE ADJUSTMENT
The vertical lines at 6 and 12 o’clock
are converged by vertically tilting the
yoke and inserting a wedge at the top
of the yoke until it is firmly seated
between the CRT glass and the horizon-
tal coils.
Yoke's Glass Cloth Tape
Wedges' Adhesive Tape (3)
Rubber Wedges (3)
Deflection Yoke
Purity & Convergence
Magnet Assembly Unit
6 Pole
Purity Magnet
4 Pole
Ring
Pairs
6 Pole
Convergence
R&B over G
Convergence
R over B
4 Pole
Rotation direction
of Both Tabs
Opposite
Opposite
Same
Same
Movement of Red
and Blue Beams
B
B B
R R
B
BR
R
B
R
R
OR
OR
OR
B
B
R
R
OR
CRT Rin
g
Location Purit
y
A
d
j
ust Tabs Beam Movement
for Convergence