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Service Adjustments (Electronic Controls, cont.)
Procedure:
1.
Apply a Color bar pattern.
2.
Connect oscilloscope to TP47B (Blue Output) in
A-board, below IC101.
3.
Select DAC Sub-Tint (B1) and adjust waveform so
that peaks 7 is halfway between peaks 5 and 6 as
shown in Fig. 24
4.
Connect oscilloscope to TP47R (Red Output), in
A-Board, below IC101.
5.
Select DAC Sub-Color B(0) and adjust for
waveform to measure 1.3V ± 0.05Vp-p, See
Fig. 25
6.
Remove jumpers (Preparation step 3).
7.
Set DAC S3 to 1.
8.
Confirm that the phase can be changed about
± 30
o
by TINT CONTROL. (Tint ratio AB=1, AC=2).
Color Temperature Adjustment
(B/W Tracking)
Serviceman DAC Adjust. (C0) (C1) (C2) (C4) (C5)
Minor Touch-Up Method
OBSERVE low and high brightness areas of a B/W
picture for proper tracking. Adjust only as required for
“good gray scale and warm highlights”.
1.
LOW LIGHT areas – In Serviceman Mode for
making electronic adjustments, select Cutoff (C0)
RED, (C1) GRN, (C2) BLU and adjust the picture
for gray.
2.
HIGH LIGHT areas – In Serviceman Mode for
making electronic adjustments, select Drive (C4)
GREEN, (C5) BLUE and adjust the picture for
warm whites.
Complete Adjustment
Preparation:
1.
Turn the Receiver “ON” and allow 45 minutes
warm up at high brightness.
2.
Apply a color bar signal with color “OFF”.
3.
Set Picture Icon Menu Video controls to Normalize.
4.
Turn the SCREEN control (part of FBT T551) fully
counterclockwise.
5.
Set Service Switch On:
Connect a jumper from Q451 (Base) to R812 +5V
side. (TPA146 or IC882-3)
6.
Preset the following Serviceman DACs for best
results:
• Red Cut-Off
C0 . . . 128
• Green Cut-Off C1 . . . 128
• Blue Cut-Off
C2 . . . 128
• Green Drive
C4 . . . . 64
• Blue Drive
C5 . . . . 64
Procedure:
1.
Connect the oscilloscope to TP47R.
2.
In Serviceman Mode for making electronic
adjustment, select the Sub-Bright DAC (B2).
3.
Observe oscilloscope waveform and adjust
serviceman mode Sub-Bright DAC (B2) until 2.5V
above DC ground is measured (See Fig. 26)
4.
Connect scope to RED Cathode (KR) on
CRT-Board
5.
In Serviceman mode for making electronic
adjustments, select RED CUTOFF DAC (C0)
6.
View scope trace at Horizontal rate and adjust
Serviceman Mode DAC (C0) for the scanning
period to be 170V for 25in models and 160V for
20in models above DC ground (See Fig. 27.)
7.
Write the same data (C0 register value) to Green
C1 and Blue C2.
8.
Turn SCREEN VR (Part of FBT) slowly clockwise
until a faint horizontal line in color appears.
9.
Using the Serviceman Mode Dac CUTOFF
adjustments, increase their setting to produce a
white horizontal line.
10. Confirm a good gray scale by viewing B/W color
bar Pattern.
11. If correction is needed perform Minor Touch-Up
Method.
12. Perform Sub-Brightness adjustment procedure if
needed.
1
3
4 5 6 7 8
a
b
a = b
2
A
B
C
Figure 24. TP47B waveform (A-Board)
1 2 3 4 5
6 7 8 9 10
Figure 25. TP47R waveform
1.3Vp-p±0.05V
0V DC
Figure 26. TP47R Waveform
2.5V DC
Figure 27. KR Waveform
Cathode Waveform.
170V DC for 25”
0V DC
(Ground)
160V DC for 20”