Zenith CM-150 Series, Service Manual

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CM150/PV150 3-8 GM CHASSIS
SERVICE ADJUSTMENTS
VERTICAL-TILT W EDGE 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 horizontal coils.
HORIZONTAL-TILT W EDGE ADJUSTMENT
The vertical lines at 3 o’clock and 9 o’clock are converged
by horizontally tilting the yoke and inserting a wedge.
First, at 4 or 8 o’clock, whichever has the larger space,
until it is firmly seated between the CRT glass and yoke
coils. Then insert the 3rd wedge in the
remaining
horizontal tilt position until firmly seated between the
CRT glass and yoke coils. Convergence at 3 and 9 o’clock
should be maintained during this operation.
When the 3 wedges are firmly installed for acceptable
convergence lock the wedges in place by applying a strip
of tape (2.5 inches long) across the tabs of each wedge,
firmly against the CRT glass.
The CRT glass surface
should be clean and free of dust and other foreign
material.
NOTE: Yoke alignment only applies to GM Direct
View 3 2” models.
UNUSUAL TILT CASE
There may be some cases where the picture tube and
yoke will require vertical tilt in the opposite (or up)
direction to obtain convergence. In such cases, insert
the vertical tilt wedge at the bottom (or “6" o’clock)
position. Follow through the horizontal tilt adjustment
by using the 2 and 10 o’clock position and secure each
wedge with a piece of tape as described above.
IMPROVING CRT CORNER PURITY
CRT’s that display corner purity problems even after
following service procedures can be modified with a
picture correction kit (P/N 949-50). The purity can be
improved by placing a picture correction magnet
(included in the kit) on the CRT funnel. Refer to the
following modification steps and illustration to place
the magnet properly.
MODIFICATION
1. Place the magnet on the CRT funnel as shown, in the
quadrant exhibiting impurity.
2. Rotate the magnet in place to the position shown for
best purity.
3. Place a piece of 1/2" by 2" Fiberglass tape over the
magnet to hold it in place.
4. Degauss the CRT once the magnet is in place to insure
that the magnet is not over the internal magnet
shield.
NOTE: If the magnet is placed over the internal
magnet shield, any apparent purity correction
will disappear after degaussing. Reposition
the correction magnet off the internal shield
and degauss again
2" To 3"
X
4 Pole Magnets
Clamp and Screw
6 Pole Magnets
2 Pole Magnets
DIRECT VIEW (continued)