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Electrical Adjustments - Toshiba 27A41 Service Manual

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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.
Inferior silicon grease can damage IC's and transistors.
When replacing IC's and transistors, use only specified
silicon grease.
Remove all old silicon before applying new silicon.
Prepare the following measurement tools for electrical
adjustments.
1. Oscilloscope
2. Digital Voltmeter
3. AC Voltmeter
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
---
04
H. POSI
05
V. POSI
06
H. SIZE
07
V. SIZE
08
V. CENT
09
V. LIN
10
VS. CORR
11
G. DRV
12
B. DRV
13
R. BIAS
14
G. BIAS
15
B. BIAS
16
BRI

ELECTRICAL ADJUSTMENTS

TV
15
Fig. 1-1
NO.
FUNCTION
17
SUBCONT
18
UNI COL
19
---
20
TINT
21
SHARP
22
RGB CONT
23
PARABOLA
24
TRAPEZIU
25
COR TOP
26
COR BTM
27
V EHT
28
H EHT
29
FM. LVL
30
LEVEL
31
SEP1
32
SEP2
33
T. STE
Fig. 1-2
2. BASIC ADJUSTMENTS
2-1: CONSTANT VOLTAGE
1.
Set condition is AV MODE without signal.
2.
Connect the digital voltmeter to TP002.
Adjust the VR502 until the digital voltmeter is 135 ± 0.5V.
3.
2-2: RF AGC
1.
Receive the VHF LOW (61dB).
2.
Connect the digital voltmeter between the TP001 and
the GND.
3.
Activate the adjustment mode display of Fig. 1-1 and
press the channel button (02) on the remote control to
select "RF. AGC".
4.
Press the VOL. UP/DOWN button on the remote
control until the digital voltmeter is 2.4V.
2-3: CUT OFF
1.
Adjust the unit to the following settings.
G. DRIVE=64, B. DRIVE=64, R. BIAS=15, G. BIAS=15,
B. BIAS=15, BRIGHT=75, UNI COLOR=64
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.
2-4: WHITE BALANCE
NOTE: Adjust after performing CUT OFF adjustment.
1.
Place the set with Aging Test for more than 10 minutes.
2.
Receive the white 100% signal from the Pattern
Generator.
3.
Using the adjustment control, set the brightness and
contrast to normal position.
4.
Activate the adjustment mode display of Fig. 1-1 and
press the channel button (13) on the remote control to
select "R. BIAS".
5.
Using the VOL. UP/DOWN button on the remote control,
adjust the R. BIAS.
6.
Press the CH. UP/DOWN button on the remote control to
select the "G. DRV", "B. DRV", "G. BIAS" or "B. BIAS".
7.
Using the VOL. UP/DOWN button on the remote control,
adjust the G. DRV, B. DRV, G. BIAS or B. BIAS.
8.
Perform the above adjustments 6 and 7 until the white
color is looked like a white.
2-5: FOCUS
1.
Receive a 70dB monoscope pattern.
2.
Turn the Focus Volume fully counterclockwise once.
3.
Adjust the Focus Volume until picture is distinct.
2-6: HORIZONTAL POSITION
1.
Receive the center cross signal from the Pattern
Generator.
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 (04) on the remote control to
select "H. POSI".
4.
Press the VOL. UP/DOWN button on the remote
control until the right and left screen size of the vertical
line becomes the same.

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