Before Making Electrical Adjustments; Basic Adjustments - Toshiba 20AS22 Service Manual

1. BEFORE MAKING ELECTRICAL
ADJUSTMENTS
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
2. Use the Channel UP/DOWN button or Channel button
(0-9) on the remote control to select the options shown
in Fig. 1-2.
3. Press the MENU button on the remote control to end
the adjustments.
NO. FUNCTION
00 OSD H
01 CUT OFF
02 RF AGC
03 VIF VCO
04 H.VCO
05 H.PHASE
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
ELECTRICAL ADJUSTMENTS
TV
15
Fig. 1-1
NO. FUNCTION
16 CONTRAST CENT
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: RF AGC
1. Place the set with Aging Test for more than 15 minutes.
2. Receive the VHF HIGH (63dB).
3. Connect the digital voltmeter to the W043.
4. Activate the adjustment mode display of Fig. 1-1 and
press the channel button (02) on the remote control to
select "RF.AGC".
5. Press the VOL. UP/DOWN button on the remote
control until the digital voltmeter is 2.5 ± 0.05V.
2-2: CUT OFF
1. Adjust the unit to the following settings.
R.DRIVE=10, B.DRIVE=10, R.BIAS=64, G.BIAS=64,
B.BIAS=64, BRIGHTNESS=125, CONTRAST=60.
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 a broadcast.
2. Turn the Focus Volume fully counterclockwise once.
3. Adjust the Focus Volume until picture is distinct.
2-5: VIF VCO
1. Place the set with Aging Test for more than 10 minutes.
2. Receive the monoscope pattern.
3. Connect the digital voltmeter between the pin 5 of
CP601 and the GND.
4. Activate the adjustment mode display of Fig. 1-1 and
press the channel button (03) on the remote control to
select "V.VCO".
5. Press the VOL. UP/DOWN button on the remote
control until the digital voltmeter is 2.5V.