Focus Adjustment; Purity Adjustment - Sylvania 6427FF Service Manual

19. Focus Adjustment

Purpose: Set the optimum Focus.
Symptom of Misadjustment: If Focus Adjustment is
incorrect, blurred images are shown on the display.
Test Point Adj. Point
--- Focus Control
Tape M. EQ.
Pattern
---
Generator
Note: Focus VR (FBT) --- Main CBA,
FBT = Fly Back Transformer
1. Operate the unit more than 30 minutes.
2. Face the unit to the East and Degauss the CRT
using Degaussing Coil.
3. Input the Monoscope Pattern.
4. Adjust the Focus Control on the FBT to obtain
clear picture.
The following adjustments normally are not
attempted in the field. Only when replacing the
CRT then adjust as a preparation.

20. Purity Adjustment

Purpose: To obtain pure color.
Symptom of Misadjustment: If Color Purity
Adjustment is incorrect, large areas of color may not
be properly displayed.
Test Point Adj. Point
Deflection Yoke
---
Purity Magnet
Tape M. EQ.
Pattern
---
Generator
Figure
GREEN
1. Set the unit facing east.
2. Operate the unit for over 30 minutes before
adjusting.
3. Fully degauss the unit using an external
degaussing coil.
Mode Input
--- Monoscope
Spec.
See below
Mode Input
--- Red Color
Spec.
See below
RED BLUE
Fig. 5
4. Loosen the screw on the Deflection Yoke Clamper
and pull the Deflection Yoke back away from the
screen. (See Fig. 6)
5. Loosen the Ring Lock and adjust the Purity
Magnets so that a red field is obtained at the
center of the screen. Tighten Ring Lock. (See Fig.
5,6)
6. Slowly push the Deflection Yoke toward bell of
CRT and set it where a uniform red field is
obtained.
7. Tighten the clamp screw on the Deflection Yoke.
21. VRS Adjustment
1. Connect Oscilloscope and get the cross hatch
pattern.
2. Adjust the two magnets for VRS adjustment like
the below figure so that the cross hatch pattern
becomes flat.
5-7 L3800EA