White Balance - Panasonic CT-1388YD Service Manual

Service adjustments (electronic controls, continued)

White balance

Service DACs (C00) (C01) (C02) (C03) (C04) (C05)
Preparation:
1. Turn the receiver "ON" and allow 30 minutes warm
up at high brightness (White screen).
2. Preset the following service DACs:
• C00 . . . . . . . . 0 255
• C01 . . . . . . . . 0 255
• C02 . . . . . . . . 0 255
• C03 . . . . . . . . . . 80
• C04 . . . . . . . . . . 80
• C05 . . . . . . . . . . 80
3. Confirm with black-white pattern and a white
screen the actual balance (gray scale and white
level). If white balance is required perform the
procedure steps as follow.
Procedure:
CUT-OFF adjustment (low lights)
1. Apply a black-white pattern.
2. Connect a jumper from Q452-Base to cold
ground ( ). ( Or apply +2.5 V D.C. to TP1 and cold
ground ( ) ) to dis-habilitate the neck protector
circuit.
3. Set red Cut-Off (C00) and blue Cut-Off (C02)
registers to 00.
4. Press R-Tune in the remote control (to close the
vertical circuit and get green horizontal line), for
models with no remote press ACTION on TV when
DAC is displayed on screen.
5. Connect scope probe between GK (C-Board) and
cold ground ( ).
6. Measure waveform and adjust register G-Cut Off,
C01, for the scanning period to be 195V for 27",
175V for 20" and 140V for 13", (see Fig. 26)
195V DC for 27"
140V DC for 13"
175V DC for 20"
Figure 27. GK waveform
7. Adjust screen VR (at T551, Flyback) until the green
line just becomes visible.
8. Press R-Tune in remote to open vertical, for
models with no remote press ACTION on TV when
DAC is displayed on screen.
9. Select red Cut-Off (C00) register, press R-Tune to
see green horizontal line. Increase C00 (volume )
until the line just become yellow (by mixing green
and red).
10. Press R-tune to open the vertical, for models with
no remote press ACTION on TV when DAC is
displayed on screen.
11. Select blue Cut-Off (C02) register, press R-Tune to
12. Press R-Tune to open the vertical, for models with
13. Confirm that a good gray scale is established by
White balance (high lights)
1. Using a black-white pattern and white screen,
Observe high light areas, if white turns reddish,
2. Exit service mode.
3. In "picture" menu, adjust "picture" and "bright"
4. If correction is needed repeat step 1 until obtain a
5. After high lights adjustment is satisfactory, perform
White balance touch-up procedure
(This procedure can be used as a minor adjustment
procedure if required)
1. Enter service mode
2. Apply
3. Observe low and high brightness areas for proper
0V DC
(Ground)
Since low level adjustment has a minor effect on high
light adjustment levels than vice versa, is recommend
perform this adjustment at the end.
4. Exit service mode turn off the set. Remove all
- 28 -
close the vertical and see the yellow line, for
models with no remote press ACTION on TV when
DAC is displayed on screen. Increase C02 (volume
) until line just becomes white (mixing green, red
and blue).
no remote press ACTION on TV when DAC is
displayed on screen.
viewing Black-White pattern.
adjust red drive (C03) and blue drive (C05) to
obtain correct white level on the screen.
decrease red drive register, on the other hand, if
white turns bluish, decrease blue drive register.
menu adjustments from low scale to high scale and
check the black and white tracking.
correct balance.
touch-up procedure as follow.
a black and
(recommended with gray tones also).
tracking.
• HIGHT LIGHT areas - Adjust red drive register
(C03) and Blue drive register (C05) for warm
whites.
• LOW LIGHT areas - Adjust red cut-off register
and blue cut-off register for proper black-gray
connections from chassis.
white image signal