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PURITY AND CONVERGENCE ADJUSTMENTS
PURITY ADJUSTMENT
1. When replacing picture tube or deflection yoke, mount
deflection yoke and purity-convergence magnets assembly
properly. See Figure 1. Position the picture tube facing east
or west. Demagnetize the picture tube and receiver using
an external degaussing coil. Set receiver to TV Service
Menu No. 73 (no vertical sweep) while degaussing.
2. Place the yoke on tube neck fully forward against glass.
Place the CPM on the tube neck aligning the center of the
purity magnet tabs (2 pole) over center of Focus Gap (G3 &
G4). See Figure 2.
3. Connect a color bar generator to the antenna terminal.
Switch the generator to a white field. Move yoke backward
on the neck until a uniform white field is obtained.
4. Allow 30 minutes warm up on a blank white field (high
intensity grayscale).
Note: If white field cannot be obtained, check Grayscale
Adjustments on page 6.
5. Set the picture controls to the Auto levels. Select a green
raster, either with the signal generator or by adjusting the
bias controls. If a signal generator is used for this step, Skip
to Step 10. If the bias controls will be used, go to step 6.
6. Adjust TV Service Menu No. 15 RB (R-Bias), No. 16 GB
(G-Bias), and No. 17 BB (B-Bias) data to 0 each.
7. Select TV Service Menu No. 73 (no vertical sweep).
8. Adjust the screen control counterclockwise until the
horizontal scan lines is no longer visible.
9. Select TV Service Menu No. 16 GB (G-Bias) and raise the
data to produce green raster. If retrace lines appear, reduce
screen control slightly.
10. Pull yoke back on the tube neck to obtain three-color raster
(blue, green and red).
11. Adjust the angle between the two purity magnet tabs to
center the vertical green belt in the picture tube. Do not
rotate tabs. See Figure 3.
12. Slowly slide the deflection yoke forward until a uniform
green screen is obtained.
13. Check the purity of the red and blue screens for uniformity.
Turn off other colors to check (use bias controls) or use
generator. If necessary, readjust the yoke position until all
screens are pure.
14. If bias controls and screen control were used to set purity,
reset Grayscale. Refer to Grayscale Adjustment on page 6.
15. Confirm that the yoke is not tilted. Tighten the yoke
mounting screw. Adjust convergence next.
CAUTION: Purity and Convergence adjustments have been made at the factory. Readjustments should be made
only after the picture tube or deflection yoke is replaced. Follow the steps below for the necessary readjustments.
