Philips MAGNAVOX 20MC4304 Service Manual page 111

13. Head Switching Position Adjustment
Purpose: Determine the Head Switching Position dur-
ing Playback.
Symptom of Misadjustment: May cause Head
Switching Noise or Vertical Jitter in the picture.
Note: Unit reads Head Switching Position automati-
cally and displays it on the screen (Upper Left Corner).
1. Playback test tape (VFMS0001H6).
2. Enter the Service mode. (See page 1-9-1.)
Then press the number "5" button on the remote
control unit.
3. The Head Switching position will display on the
screen; if adjustment is necessary follow step 4.
6.5H(412.7µs) is preferable.
4. Press "CH o" or "CH p" button on the remote con-
trol unit if necessary. The value will be changed in
0.5H steps up or down. Adjustable range is up to
9.5H. If the value is beyond adjustable range, the
display will change as:
Lower out of range: 0.0H
Upper out of range: -.-H
5. Turn the power off and on again.
The following 2 adjustments normally are not
attempted in the field. They should be done
only when replacing the CRT then adjust as a
preparation.
14. Purity Adjustment
Purpose: To obtain pure color.
Symptom of Misadjustment: If Color Purity Adjust-
ment is incorrect, large areas of color may not be prop-
erly displayed.
Test point Adj. Point
Deflection Yoke
---
Purity Magnet
Tape M. EQ.
--- Pattern Generator
GREEN
* This becomes RED COLOR if the 7KEY is pressed
while in service mode.
1. Set the unit facing east.
2. Operate the unit for over 30 minutes before adjust-
ing.
3. Fully degauss the unit using an external degauss-
ing coil.
4. Set the unit to the AUX mode which is located
before CH2 then input a red raster from video in.
5. Loosen the screw on the Deflection Yoke Clamper
and pull the Deflection Yoke back away from the
screen. (See Fig. 9.)
6. Loosen the Ring Lock and adjust the Purity Mag-
nets so that a red field is obtained at the center of
the screen. Tighten Ring Lock. (See Fig. 8,9.)
7. Slowly push the Deflection Yoke toward the bell of
the CRT and set it where a uniform red field is
obtained.
8. Tighten the clamp screw on the Deflection Yoke.
1-9-8
Mode Input
--- *Red Color
Spec.
See below.
Figure
RED
BLUE
Fig. 8
T1006EA