Panasonic CT-25G6UE Service Manual - Page 22

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Panasonic CT-25G6UE Service Manual
Service Adjustments (Electronic Controls)
Note: It is recommended to allow for a 30 minute
warm up period, at high brightness level (use
white screen), prior to any picture adjustment.

Sub-Contrast

Service DAC Adjustment (B3)
This adjustment is factory set. Do not adjust unless
repairs are made to associated circuit, the CRT Board
or when the CRT is replaced.
Preparation:
1. Apply a color bar signal pattern with 87.5%
modulation, 70% saturated color bar with a 100
IRE white and 7.5 black.
Note:
The pattern used in this procedure is an EIA color
bar pattern with 87.5% modulation with 100 IRE
white and 7.5 black. Correlate the information in this
procedure to the pattern used if another signal
is used.
2. Preset the following controls:
•
Brightness . . . . . . . Center.
•
Picture . . . . . . . . . . Max.
•
Sharpness . . . . . . . Center.
γ Gamma (S5) . . . . 15
•
•
ACL OFF (CA) . . . . 00
•
Cut Off G (C1) . . . . 00
3. Connect the oscilloscope to the CRT-Board
connector C1-2 (TP35). Set the scope time base to
20µs (horizontal).
Procedure:
1. In the Service Mode, select DAC Sub-Contrast
Adjustment (B3) and adjust for 2.5 ±0.1Vp-p
between white and black level. (See video
waveforms detail, Fig. 18).
2.5V
±0.1V
p-p
Figure 18. TP35 waveform
2. Following adjustments set S5, CA & C1 to their
original settings.
3. Turn Receiver OFF and disconnect test equipment.

Sub-Brightness

Service DAC Adjustment (B2)
Due to the characteristics of this chassis, Sub-
brightness adjustments are not necessary. For good
brightness level set the register to "127", the default
level.
Perform "Sub-Brightness Final Adjustment" on page 23
only if a different brightness level is required for the
picture.

Tint/Color Adjustment

Service DAC Adjustment (B1) (B0)
Preparation:
1. Apply a rainbow color bar signal.
2. Preset the following controls:
•
Brightness . . . . . . . Min.
•
Color . . . . . . . . . . . Center.
•
Tint. . . . . . . . . . . . . Center.
•
Picture . . . . . . . . . . Max.
•
Sharpness . . . . . . . Min.
γ, Gamma (S5). . . . 15
•
•
ACL OFF (CA) . . . . 00
3. Connect the oscilloscope to TP37 (or C1-3).
Procedure:
1. In the Service Mode for making electronic
adjustments, select DAC Sub-Tint Adjustment
(B1). Adjust until the waveform measured is as the
one shown in Fig. 19.
TP47B (A-Board)
Figure 19. TP37 waveform
2. Connect the oscilloscope to TP35 (C-Board) and
GND.
3. Select DAC Sub-Color Adjustment (B0) and adjust
for peak to peak amplitude to be 0.8Vp-p ±0.05V
as shown in Fig. 20.
TP35 (C-Board)
Figure 20. TP35 waveform
4. Following adjustments, reset controls modified
during preparation to their original levels
5. Turn Receiver OFF and disconnect test equipment.
White Balance
Service DACs. (C0) (C1) (C2) (C3) (C4) (C5)
Preparation:
1. Turn the Receiver "ON" and allow 30 minutes
warm up at high brightness (white screen).
2. Preset the following DACs:
•
C0: Cut Off_R . . . . 0 255
•
C1: Cut Off_G . . . . 0 255
•
C2: Cut Off_B . . . . 0 255
•
C3: Drive_R . . . . . . 80
•
C4: Drive_G . . . . . . 80
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0.8Vp-p±0.05V