Samsung CT20F3FNT, Service Manual

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Alignment and Adjustments
Samsung Electronics 4-5
4-3-3 High Voltage Check
CAUTION: There is no high voltage adjustment on this chassis.
The B+ power supply must be set to +122.5 volts (Full color bar
input and normal picture level).
1. Connect a digital voltmeter to the second
anode of the picture tube.
2. Turn on the TV. Set the Brightness and
Contrast controls to minimum (zero beam cur-
rent).
3. The high voltage should not exceed 30KV.
4. Adjust the Brightness and contrast controls to
both extremes. Ensure that the high voltage
does not exceed 30KV under any conditions.
4-3-4 FOCUS Adjustment
1. Input a black and white signal.
2. Adjust the tuning control for the clearest pic-
ture.
3. Adjust the FOCUS control for well defined
scanning lines in the center area of the screen.
4-3-5 Cathode Voltage Adjustment
(Screen Adjustment)
1. Connect CRT socket pin GK to an oscilloscope
probe.
2. Input a gray scale pattern. (Use a pattern gen-
erator, PM5518)
3. Use the P mode key (on the remote control)
for the STANDARD picture.
4. Adjust the Screen VR (on the FBT) so that the
voltage on the oscilloscope becomes 125+2.5V
(See Fig. 4-1).
4-3-6 Purity Adjustment
1. Warm up the receiver for at least 20 minutes.
2. Plug in the CRT deflection yoke and tighten
the clamp screw.
3. Plug the convergence yoke into the CRT and
set in as shown in Fig. 4-2.
4. Input a black and white signal.
5. Fully demagnetize the receiver by applying an
external degaussing coil.
6. Turn the CONTRAST and BRIGHTNESS con-
trols to maximum.
7. Loosen the clamp screw holding the yoke.
Slide the yoke backward or forward to pro-
vide vertical green belt. (Fig. 4-3).
8. Tighten the convergence yoke.
9. Slowly move the deflection yoke forward,
and adjust for the best overall green screen.
10. Temporarily tighten the deflection yoke.
11. Produce blue and red rasters by adjusting the
low-light controls. Check for good purity in
each field.
12. Tighten the deflection yoke.
Fig. 4-1
125 2.5V
+_
GND
_