Changhong Electric PF2939, Service Manual, Page: 36 / 47

SERVICE MANUAL
ADJUSTMENTS
Set-up Adjustments
● The following adjustments should be made when a complete realignment is required or a new
CRT is installed. Perform the adjustments in order as follows.
1. Color purity
2. Convergence
3. White Balance
Note
：
The purity/convergence magnet assembly and rubber wedges need mechanical positioning.
Refer to Fig. 15.
1. Color Purity Adjustment
Note
：
Before attempting any purity adjustment, the TV should be operated for at least 15 minutes.
1) Demagnetize the CRT and cabinet using a degaussing coil.
2) Set the brightness and contrast to maximum.
3) Receive the green raster test pattern.
4) Loosen the clamp screw holding the deflection yoke and slide it backward or forward to display
vertical green belt (zone) on the screen.
5) Remove the rubber wedge.
6) Rotate and spread the tabs of the purity magnet around the neck of the CRT until the green belt
is on the center of the screen.
7) Slowly move the deflection yoke forward or backward until a uniform green screen is obtained.
Tighten the clamp screw of the yoke temporarily.
8) Check purity of the red and blue raster.
Yoke
Fig. 15
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