Panasonic CT-25G6UE Service Manual - Page 23
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•
C5: Drive_B . . . . . .80
3. Confirm using Black & White pattern and a white
screen the color balance (gray scale and white
balance). If white balance is required perform the
following:
Procedure (Low Lights):
1. Apply a Black & White pattern.
2. Connect a jumper from the base of Q452 to cold
ground (
) (or apply +2.5V DC to TP1 to defeat
the neck protector circuit).
3. Set the Red and Blue Cut-Off registers (C0 and
C2) to 00.
4. On the Remote Control, press R-Tune to get a
green horizontal line.
5. Connect the scope between GRN Cathode (GK, on
the CRT-Board) and cold ground (
6. View scope trace at Horizontal rate and adjust the
Service Mode DAC (C1) level until a scanning
period of 195V above DC ground is measured, as
indicated in Fig. 21.
Figure 21. Cathode Waveform, Adjustment
Waveform Detail
7. Adjust screen VR (on T551, Flyback) until the
green line just becomes visible.
8. Press R-Tune (on Remote Control) to display full
screen.
9. Select Red Cut-Off register (C0). Press R-Tune to
display a green horizontal line. Increase C0 value
(using Volume u) until the line turn yellow (mixing
green & red).
10. Press R-Tune to display full screen.
11. Select Blue Cut-Off register (C2) and press R-Tune
to see the yellow line. Increase C2 value (using
Volume u) until the line becomes white (mixing red
blue and green).
12. Press R-Tune to display full screen.
13. Confirm that a good gray scale is displayed when
viewing a Black & White pattern.
14. EXIT the Service Mode.
White Balance (High Lights)
1. Using a Black and White pattern and white screen
adjust Red Drive, C3, and Blue Drive, C5 to obtain
good white level on screen. If white looks reddish,
decrease C3, if white looks bluish, decrease C5.
2. Exit Service Mode.
3. In Picture menu change Picture and Brightness
from low to high scales and observe black and
white tracking.
4. If corrections are required, repeat step 1 until the
correct balance is achieved.
5. Following satisfactory High Lights adjustment
perform the following White Balance Touch-Up.
White Balance Touch-Up Procedure:
Use this procedure to make minor adjustment to white
balance.
1. Enter Service Mode.
2. Apply a black and white (B/W) signal (signal that
includes gray tones).
3. Observe low and high brightness areas of a B/W
picture for proper tracking. Adjust the following as
required for "good gray scale and warm highlights":
•
HIGH LIGHT areas – Adjust Red Drive (C3) and
Blue Drive (C5) registers until picture appear best
for warm whites.
•
LOW LIGHT areas – adjust Red Cut-Off (C0) and
Blue Cut-Off (C2) registers until best picture for
black-gray.
Due to effect from low level adjustment on high level
).
adjustment, it is recommended that this procedure is
done at the end of the adjustments procedure.
4. Exit Service Mode.
5. Remove all external connections made to the
Receiver.
Sub-Brightness Final Adjustment
Service DAC Adjustment (B2)
195VDC
This adjustment should be made last, following
other picture adjustments.
0V DC
Preparation:
1. Turn the Receiver ON and allow 20 minute warm
up at high brightness (white screen).
2. Apply a black and white cross pattern.
3. Set PICTURE to Max.
4. Set BRIGHT to Center.
Procedure:
1. In Service Mode, select Sub Bright register (B2).
2. Adjust B2 until the 7.5 IRE section looks same as
3.0 IRE section as seen in Fig. 22.
3. Exit Service Mode.
Horizontal Centering
Service DAC Adjustment (C9)
Preparation:
Connect a monoscope generator.
Procedure:
1. In the Service Mode, select the Horizontal
Centering Adjustment DAC (C9). Adjust it until
locations "A" and "B" are even on both sides of
screen, as indicated in Fig. 23.
2. EXIT the Service Adjustment Mode.
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Figure 22. Sub-bright adjustment