Toshiba 20A23 Service Manual - Page 13

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Toshiba 20A23 Service Manual

1. ADJUSTMENT PROCEDURE

Read and perform these adjustments when repairing the
circuits or replacing electrical parts or PCB assemblies.
CAUTION
•
Use an isolation transformer when performing any service
on this chassis.
•
Before removing the anode cap, discharge electricity
because it contains high voltage.
•
When removing a PCB or related component, after
unfastening or changing a wire, be sure to put the wire
back in its original position.
•
When you exchange IC and Transistor for a heat sink,
apply the silicon grease on the contact section of the heat
sink. Before applying new silicon grease, remove all the
old silicon grease. (Old grease may cause damages to the
IC and Transistor.)
Prepare the following measurement tools for electrical
adjustments.
1. Oscilloscope
2. Digital Voltmeter
3. Pattern Generator
On-Screen Display Adjustment
1. In the condition of NO indication on the screen.
Press the VOL. DOWN button on the set and the Channel
button (9) on the remote control for more than 1 second to
appear the adjustment mode on the screen as shown in
Fig. 1-1.
00 OSD
3.
Use the Channel UP/DOWN button or Channel button
(0-9) on the remote control to select the options shown
in Fig. 1-2.
4.
Press the MENU button on the remote control to end the
adjustments.
NO.
FUNCTION
00
OSD H
01
CUT OFF
04
H.VCO
05
H.PHAS
06
V.SIZE
07
V.SHIFT
08
R.DRIVE
09
B.DRIVE
10
R.BIAS
11
G.BIAS
12
B.BIAS
13
BRIGHT CENT
14
BRIGHT MAX
15
BRIGHT MIN
16
CONTRAST CENT

ELECTRICAL ADJUSTMENTS

TV
17
Fig. 1-1
NO.
FUNCTION
17
CONTRAST MAX
18
CONTRAST MIN
19
COLOR CENT
20
COLOR MAX
21
COLOR MIN
22
TINT
23
SHARPNESS
24
FM LEVEL
25
LEVEL
26
SEPARATION 1
27
SEPARATION 2
28
TEST MONO
29
TEST STEREO
30
X-RAY TEST
Fig. 1-2

2. BASIC ADJUSTMENTS

2-1: CONSTANT VOLTAGE
1.
Set condition is AV MODE without signal.
2.
Connect the digital voltmeter to the TP402.
Adjust the VR502 until the digital voltmeter is 117 ± 1V.
3.
2-2: CUT OFF
1.
Adjust the unit to the following settings.
R.DRIVE=10, G.DRIVE=10, R.BIAS=64, G.BIAS=64,
B.BIAS=64, BRI CENT=130, CONT MAX=80.
2.
Place the set with Aging Test for more than 15 minutes.
3.
Activate the adjustment mode display of Fig. 1-1 and
press the channel button (01) on the remote control to
select "CUT OFF".
4.
Adjust the Screen Volume until a dim raster is obtained.
2-3: WHITE BALANCE
NOTE: Adjust after performing CUT OFF adjustment.
1.
Place the set with Aging Test for more than 10 minutes.
2.
Receive the gray scale pattern from the Pattern Generator.
3.
Using the remote control, set the brightness and contrast
to normal position.
4.
Activate the adjustment mode display of Fig. 1-1 and
press the channel button (10) on the remote control to
select "R. BIAS".
5.
Press the CH. UP/DOWN button on the remote control to
select the "R. BIAS", "G. BIAS", "B. BIAS", "R. DRIVE" or
"B. DRIVE".
6.
Adjust the VOL. UP/DOWN button on the remote control
to whiten the R. BIAS, G. BIAS, B. BIAS, R. DRIVE, and
B. DRIVE at each step tone sections equally.
7.
Perform the above adjustments 5 and 6 until the white
color is looked like a white.
2-4: FOCUS
1.
Receive the monoscope pattern.
2.
Turn the Focus Volume fully counterclockwise once.
3.
Adjust the Focus Volume until picture is distinct.
2-5: HORIZONTAL PHASE
1.
Receive the monoscope pattern.
2.
Using the remote control, set the brightness and contrast
to normal position.
3.
Activate the adjustment mode display of Fig. 1-1 and
press the channel button (05) on the remote control to
select "H. PHAS".
4.
Press the VOL. UP/DOWN button on the remote control
until the SHIFT quantity of the OVER SCAN on right and
left becomes minimum.
D-1