DAEWOO DTQ-20P1FC Service Manual
CONTROL VIEW
REMOCON SENSOR
ENTER
MENU
F-CONNECTOR
VHF
POWER ON/OFF
CH UP/DN
VOL UP/DN
300 OHM-75 OHM
COUPLING
TRANSFORMER
75
FROM 75 OHM
VHF ANTENNA WITH
CABLE OR CABLE
TV SYSTEM
3
IMPORTANT SERVICE NOTES
1. X-RAY RADIATION PRECAUTION
1) Excessive high voltage can produce potentially
hazardous X-RAY RADIATION. To avoid such
hazards, the high voltage must not be above the
specified limit. The nominal value of the high voltage
of this receiver is 24.4kv(28.6kv) at zero beam current
(minimum brightness) under a 120V AC power source.
*
The high voltage must not, under any circumstances,
exceed 25kv (29kv). Each time a receiver requires
servicing, the high voltage should be checked following
the HIGH VOLTAGE CHECK procedure on page 7 of
this manual. It is recommended as a parts of the
service record. It is important to use an accurate and
reliable high voltage meter.
2) This receiver is equipped with X-RADIATION
PROTECTION circuit which prevents the receiver from
producing an excessively high voltage even if the
B+voltage increases abnormally. Each time the
receiver is serviced, X-RADIATION PROTECTION
circuit must be checked to determine that the circuit is
properly functioning, following the X-RADIATION
PROTECTION CIRCUIT CHECK procedure on page 7
of this manual.
3) The only source of X-RAY RADIATION in this TV
receiver is the picture tube. For continued X-RAY
RADIATION protection, the replacement tube must be
exactly the same type tube as specified in the parts list.
4) Some parts in this receiver have special safety-related
characteristics for X-RAY RADIATION protection. For
continued safety, parts replacement should be
undertaken only after referring to the PRODUCT
SAFETY NOTICE below.
2. SAFETY PRECAUTION
WARNING
: Service should not be attempted by anyone
unfamiliar with the necessary precautions on this receiver.
The following are the necessary precautions to be
observed before servicing.
1) Since the chassis of this receiver has hazardous
potential to ground whenever the receiver is plugged in
(floating chassis), an isolation transformer must be
used during servicing to avoid shock hazard.
2) Always discharge the picture tube anode to the CRT
conductive coating before handling the picture tube.
The picture tube is highly evacuated and if broken,
glass fragments will be violently expelled. Use
shatterproof goggles and keep picture tube away from
the body while handling.
3) When placing a chassis in the cabinet, always be
certain that all the protective devices are put back in
place, such as; non-metallic control knobs, insulating
covers, shields, isolation resistor-capacitor network,
etc.
4) Before returning the set to the customer, always
perform an AC leakage current check to the exposed
metallic parts of the cabinet, such as antennas,
terminals, screwheads, metal overlays, control shafts
etc. to be sure the set is safe to operate without
danger of electrical shock.
* Minimum brightness
Plug the AC line cord directly into a 120V AC outlet (do
not use a line isola-tion transformer during this check).
Use an AC voltmeter having 5000 ohms per volt or
more sensitivity in the following manner.
Connect at 1500 ohm 10 watt resistor, paralleled by a
0.15µF. AC type capacitor, between a known good
earth ground (water pipe, conduit etc.) and the
exposed metallic parts, one at a time. Measure the AC
voltage across the combination of 1500 ohm resistor
and 0.15µF capacitor. Voltage measured must not
exceed 0.3 volts RMS. This corresponds to 0.2
milliamp. AC. Any value exceeding this limit constitutes
a potential shock hazard and must be corrected
immediately.
AC VOLT METER
0.15µF
Place this probe
on each exposed
metalic part.
Good earth ground
such as a water
pipe, conduit, etc.
1500 ohm
10watt
3. PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have
special safety-related characteristics. These
characteristics are often passed unnoticed by a visual
inspection and the protection afforded by them cannot
necessarily be obtained by using replacement
components rated for higher voltage, wattage, etc.
Replacement parts which have these special safety
characteristics are identified in this manual and its
supplements; electrical components having such features
are identified by shading on the schematic diagram and
the parts list.
Before replacing any of these components, read the parts
list in this manual carefully. The use of substitute
replacement parts which do not have the same safety
characteristics as specified in the parts list may create Xray radiation or other hazards.
4. SERVICE NOTES
1) When replacing parts or circuit boards, clamp or bend
the lead wires to terminals before soldering.
2) When replacing a high wattage resistor (metal oxide
film resistor) in the circuit board, keep the resistor min
1/2 inch away from circuit board.
3) Keep wires away from high voltage or high
temperature components.
4
BLOCK DIAGRAM
- 5 -
GENERAL ADJUSTMENTS
1. GENERAL
In the majority of cases, all color televisions will need only
slight touch-up adjustment upon installation. Check the
basic characteristics such as height, focus and subbright. Observe the picture for good black and white
details without objectionable color shading. If color
shading is evident, demagentize the receiver. If color
shading still persists, perform purity and convergence
adjustments. This should be all that is necessary to
achieve Optimum receiver performance.
2. VERTICAL HEIGHT ADJUSTMENT
1) Tune in an active channel.
2) Adjust brightness and contrast controls for a good
picture.
3) Adjust vertical height control (R315) for approximately
one half inch over scan at top and bottom of picture
screen.
4) Vertical centering adjustment VR316
Horizontal centering adjustment VR556.
3. FOCUS ADJUSTMENT
1) Tune in an active channel.
2) Adjust brightness, sharpness and contrast controls for a
good picture.
3) Adjust focus control (part of T402) for sharp scanning
lines and/or sharp picture.
4. RF AGC ADJUSTMENT
1) Tune in an active channel.
2) Using the attenuator, apply the signal of 60dBm to the
antenna input terminal.
3) Turn RF AGC control (VR555) full clockwise until snow
or/and noise appears in the picture, then slowly turn
control counterclockwise until snow or/and noise
disappears.
5. HIGH VOLTAGE CHECK
High voltage is not adjustable but must be checked to
verify that the receiver is operating within safe and
efficient design limitations as specified:
1) Operate Receiver for at least 15 minutes at 120V AC
line.
2) Set brightness sharpness, contrast and color control to
minumum position (Zero beam).
3) Connect accurate high voltage meter to CRT anode.
The reading should be 24.4kv(28.6kv)
DTQ-14 ----- : 22.6kv ~ 24.6kv
(
DTQ-20 ----- : 26.1kv ~ 28.8kv
If a correct reading cannot be obtained, check circuitry for
malfunctioning components.
6. X-RADIATION PROTECTION CIRCUIT
When service has been performed on the horizontal
deflection system, high voltage system or B+ system, the
X-RADIATION protection circuit must be tested for proper
operation as follows:
)
TEST
1) Operate receiver for at least 15 minutes at 120V AC
line.
2) Adjust all customer controls for normal picture and
sound.
3) Check the voltage of D401 cathode. It's voltage
should be about 22V DC.
4) Connect the cathode of diode D302 and D401 through
a 2.7K ohm, 1/4W Resistor(R313).
5) To start operation, remove the resistor and touch the
cathode of D401 to chassis ground with a short clip
lead (Remove short clip lead as soon as the set
operates again with normal picture).
6) If the operation of horizontal osc. does not stop in step
The circuit must be repaired, before the set is returned
to the customer.
7. CRT GRAY SCALE ADJUSTMENT
1) Tune in an active channel.
2) Set the COLOR control to minimum.
3) Turn the SCREEN control (on T402 fully counterclockwise.)
4) Rotate the RED, GREEN and BLUE BIAS controls
(R971, R972, R973) counterclock wise from the
maximum, set them to the position where notches in
the knobs become parallel to the surface of P.C.
Board.
5) Set the GREEN and BLUE DRIVE controls (R975,
R974) to the mid position.
6) Turn the service switch SW20 (Service Position) on
the CRT board.
7) Rotate the SCREEN control (on T402) gradually
clockwise until the second horizontal line following the
first line appears slightly on the screen. Then turn fully
counterclockwise the two BIAS controls corresponding
to the colors of the first and the second horizontal
lines to eliminated the lines.
8) Set the SCREEN control to the position where the
third horizontal line lights slightly on the screen.
9) Adjust the two BIAS control set to the minimum in item
7) above to obtain the slightly lighted horizontal line in
the same levels of three (red, green, blue) colors. (The
line should be white if the BIAS controls are adjusted
properly.)
10) Turn the service switch SW20 again (Normal position
on the CRT board.)
11) Press PICTURE-SEL, P-UP and set the brightness
and contrast controls to the maximum.
12) Adjust the BLUE and GREEN DRIVE control to obtain
proper white-blanced picture in high light areas.
13) Using P-SEL, P-DN key, set the brightness and
contrast controls to obtain dark gray raster. Then
check the white balance in low brightness. If the white
balance is not proper, retouch the BIAS controls and
DRIVE controls to obtain a good white balance in both
low and high light areas.
7
8. SUB-BRIGHTNESS ADJUSTMENT
1) Tune in a color program.
2) Set the CONTRAST control to maximum and the BRIGHTNESS control to maximum and the SHARPNESS
control to the center position.
3) Set the COLOR and TINT controls to center.
4) Set the SUB-BRIGHT control R554 to center and leave
the receiver on five minutes in this state.
5) Watching the picture carefully, adjust the SUB-BRIGHT
control in the position where the picture does not show
evidence of blooming in high brightness area and not
appear too dark in low bright area.
6) Check for BRIGHTNESS controls at both extremes.
7) If the picture does not appear dark with the
CONTRAST and BRIGHTNESS control turned to
minimum, or not appear bright with the controls turned
to maximum, adjust the SUB-BRIGHT control again for
an acceptable picture.
9 . CONVERGENCE MAGNET ASSEMBLY
POSITIONING
If Convergence magnet assembly and rubber wedges
need mechanical positioning follow figure 2.
9-1. COLOR PURITY ADJUSTMENT
NOTE
1) Demagnetize the picture tube with a degaussing coil.
2) Adjust the CONTRAST and BRIGHTNESS controls to
3) Adjust RED and BLUE Bias controls (R971 and R973)
4) Loosen the clamp screw holding the yoke, and slide
5) Remove the Rubber Wedges.
6) Rotate and spread the tabs of the purity magnet (See
7) Move the yoke slowly forward until a uniform green
8) Check the purity of the red and blue raster by adjusting
9) Obtain a white raster, referring to
10) Proceed with covergence adjustment.
: Before attempting any purity adjustments, the
receiver should be operated for at least 15
minutes.
maximum
to provide only a green raster. Adjust the GREEN BIAS
control (R972) if necessary.
the yoke backward to provide vertical green
belt(zone)in the picture screen.
figure 2) around the neck of the picture tube until the
green belt is in the center of the screen. At the same
time, center the raster vertically.
screen is obtained. Tighten the clamp screw of the
yoke temporarily.
the BIAS controls.
CRT GRAY SCALE
ADJUSTMENT
.
RUBBER
WEDGES
PICTURE TUBE
DEFLECTION
YOKE
GLASS CLOTH
TAPE
CONVERGENCE
MAGNET ASS'Y
TEMPORARY
MOUNTING
{
30 30
30
Fig. 2 Rubber Wedges Location
RUBBER
WEDGES
ADHESIVE
DEF.
YOKE
8
9-2. CONVERGENCE ADJUSTMENTS
BLUE
BLUE
4-Pole Magnets Movement 6-Pole Magnets Movement Incline the Yoke up(or down) Incline the Yoke right(or left)
Center Convergence by Convergence Magnets Circumference Convergence by DEF. Yoke
RED
RED
RED/BLUE
RED/BLUE
GRN
GRN
B G R
BGR
R
G
B
B
G
R
R G B
R
G
B
B
G
R
BGR
NOTE
: Before attempting any purity adjustments, the
receiver should be operated for at least 15
minutes.
A. CENTER CONVERGENCE ADJUSTMENT
1) Receive crosshatch pattern with a crosshatch signal
generator.
2) Adjust the BRIGHTNESS and CONTRAST Controls for
a good picture.
3) Adjust two tabs of the 4-Pole Magnets to change the
angle between them (See Fig. 3) and superimpose red
and blue vertical lines in the center area of the picture
screen. (See Fig. 4)
4) Turn both tabs at the same time keeping their angles
constant to superimpose red and blue horizontal lines
at the center of the screen. (See Fig. 4)
5) Adjust two tabs of 6-Pole Magnets to superimpose
red/blue line with green on top of each other. Adjusting
the angle affects the vertical lines and rotating both
magnets affects the horizontal lines.
6) Repeat adjustments 3), 4), 5) keeping in mind red,
green and blue movement, because 4-Pole Magnets
and 6-Pole Magnets interact and make dot movement
complex.
B. CIRCUMFERENCE CONVERGENCE ADJUSTMENT
: This adjustment requires Rubber Wedge Kit.
NOTE
1) Loosen the clamping screw on deflection yoke to allow
the yoke to tilt.
2) Place a wedge as shown in figure 2 temporarily. (Do
not remove cover paper on adhesive part of the
wedge.)
3) Tilt front of the deflection yoke up or down to obtain
better convergence in circumference. (See Fig. 4) Push
the mounting wedge into the space between picture
and the yoke to hold the yoke temporarily.
4) Place other wedge into bottom space and remove the
cover paper to stick.
5) Tilt front of the yoke right or left to obtain better
convergence in cicumference. (See Fig. 4)
6) Hold the yoke position and put another wedge in either
upper space. Remove cover paper and stick the wedge
on picture tube to hold the yoke.
7) Detach the temporarily mounted wedge and put it in
another upper space. Stick it on picture tube to fix the
yoke.
8) After placing three wedges, re-check overall
convergence. Tighten the screw firmly to hold the yoke
tightly in place.
9) Stick 3 adhesive tapes on wedges as shown in figur3,2.
4-POLE
MAGNETS
PURITY
MAGNETS
6-POLE
MAGNETS
CONVERGENCE MAGNET ASSEMBLY
ADJUST THE
ANGLE
(VERTICAL
LINES)
Fig. 3
CONSTANT
ROTATE TWO TABS AT
THE SAME TIME
(HORIZONTAL LINES)
ADJUSTMENT OF MAGNET
Fig. 4 Dot Movement Pattern
9
10. PICTURE IF/AFT ADJUSTMENTS
NOTE
: THIS RECEIVER IS TRANSISTORIZED AND SPECIAL CARE MUST BE TAKEN WHEN SERVICING. READ
THE FOLLOWING (NOTES BEFORE ATTEMPTING ALIGNMENT)
Alignment requires an exacting procedure and should be undertaken only when necessary.
Isolation transformer must be used to prevent shock hazard.
The test equipment specified or its equivalent is required to perform the alignment properly. Use of equipment which
does not meet these requirements may result in improper alignment.
Accurate equipment is essential to obtain proper alignment of this receiver.
Use of excessive signal from a sweep generator can cause overloading of receiver circuit Overloading should be
avoided to obtain a true response curve. Insertion of markers from the marker generator should not cause distortion of
the response curve.
The AC Power line voltage should be kept 120 volts while alignment is being performed.
Do not attempt to disconnect any components while the receiver is in operation.
Make sure the power cord is disconnected before replacing any parts in the receiver.
TEST EQUIPMENT
Digital voltmeter National Model VP-2600A or equivalent
Oscilloscope
Direct/Low-capacity probe
Tektronix Model 2215A or equivalent.
Tektronix Model P6120 or equivalent
(Accessory of oscilloscope)
Color-Bar/Dot/Crosshatch generator
PIF sweep marker generator
Power supply
Isolation transformer
Tektronix Model 146 or equivalent.
Nihon Tsushinki Model 4723 or equivalent
Academy Model 150A or equivalent
Voltage adjustable type having capacity of
at least 150 watts
BLOCK DIAGRAM
B+
BIAS
POWER
SUPPLY
A
(16.5V)
AGC
BIAS
POWER
SUPPLY
B
(4-5V)
1) Disconnect the
MAIN BOARD
TP3
TP5
PIF SWEEP/MARKER GEN.
VH
Fig. 5 Picture IF Sweep Alignment
TP6
TP1
TP4
DET IN
OUT
TUNER IF output from TP1 and connect equipment as shown above.
OSCILLOSCOPE
Y
X
45.75MHz
Fig. 6 PIF Response
P
45.75MHz
Fig. 7 AFT Response Curve
2) Set the sweep/marker generator for 30 Vrms.
3) Observe 1 Vp-p on scope by adjusting power supply B (4~5V).
4) Adjust PIF coil L505 for according beat signal with 45.75 MHz marker on scope (See Fig. 6).
5) Connect the
DET IN to TP6.
6) Adjust AFT coil L504 for center display at 45.75 MHz on scope (See Fig. 7).
7) After completing the above steps, disconnect equipment and adjust the AGC delay circuit as explained in the General
Adjustments section of this manual.
10
TROUBLE SHOOTING CHARTS
NO POWER
A
RLY1
RELAY
DOES RLY1 (RELAY) OPERATE?
CHECK
IN/OUT VOLTAGES
OF I801(130VOLT REG)
IN: 150V
OUT: 130V
DC
DC
CHECK
I801
STR30130
130V
R413 18K
2WATT
R414 20K
2WATT
DC
IF #26 NORMAL
& NO OUTPUT AT
#23 THEN
CHANGE I501
16.5V
CHECK
16.5V LINE
YES
NO
CHECK
#30
(7.5V
DC
)
30
I501
26 23
Q402
H. OUTPUT
D405
24
GO TO
GO TO
T402
F.B.T
5
4
4
A
B
DOES
SHUT DOWN
CIRCUIT
OPERATE?
H.V
SHUT DOWN
OCCURS AT
22VDC
CHECK
Q402
COLLECTOR
B
5V
SHOULD
BE
4.3V-5.2V
Q708
REGULATOR
CHECK
F801
125V 4A
CHECK
LEAD
SOLDERING
Q701
RESET
R759
D710
L801
LINE FILTER
CHECK
ALL THE POINTS
THEN CHANGE
NORMAL: 5V
RESET: 0V
1
I701
2
9
23
OPEN LOAD
THEN CHECK
#23 ON STATE
4 ~5V
Q704
POWER
CONTROL
RLY1
RELAY
PWR
CONTROL
KEY
CHECK
Q704 &
RELAY
I701
KEY OPERATE?
CHECK DIODE
D701 & SWITCH
KEY BOARD
11
21
42
39
3
7
7
4
10
9
9
10
8
8
16
15
14
14112
10
44
31
11 14
C
D
H
H
GO TO
OK
CHECK THE WAVE FORM OF
I501 #44
NG
NO PICTURE
GO TO
I501
LA 7674
COMPOSITE
VIDEO INPUT
C
D
C217
Y-OUT
DRIVE
H. BLANKING
CHECK
190V
LINE
D404
Q506
VIDEO
CONTRAST
BRIGHT
CHECK
C410
R554
SUB-BRIGHT
CHECK
9V LINES
#11,14
C410
0.1 (M)
AGC
PIN 4
Q501
ABL
CHECK
CONTROL
(MAX)
VOLTAGES
#39:7.5V
#31:6.2V
12V
5V
V
T
(33V)
U001 TUNER
IF
ENA
DATA
CLK
CHECK
CRYSTAL
X701
CHECK THE
VOLTAGE
AT Q101
CHECK
IF AGC
VTG.
5V
DC
SF01
SAW FILTER
Q101
PRE-AMP
I501
LA7674
ADJUST
RF-AGC
R555
DETECTOR
OUTPUT
CHECK
9V LINE
#11, 14
TO Q504
CHECK
HEATER
VTG 6.3Vrms
R402
T402
FBT
H
I701
4241
12
4
6
30
11
1
14
44
48
4
48
E
F
GO TO
YES
CHECK FOR SIGNAL
AT I501 #6
NO
NO SOUND
GO TO
E
F
I501
LA7674
VOL-UP
DOWN
CONTROL
KEY
SOUND VOLUME
MAX: ~7V
DC
MIN: ~1V
DC
CHECK
CONNECTOR
P601
I701
CHECK
9V
DC
LINE#11,14
LOW PASS
FILTER
Q602,Q603
AUDIO
OUT
T601
TSP1036
SP01
SPEAKER
Q601
AUDIO
AMP
DISCONNECT LOAD
CHECK FOR SND,
PWM SIGNAL, IF
MISSING REPLACE
I701
SOUND TAKEOFF
NO OUTPUT:
CHANGE I501
DE EMPHASIS
CHECK
FM DET.
CIRCUIT
CHECK
R601 &
123V LINE
X601
I501
LA7674
SOUND
IF INPUT
Z601
IF #4 IS OK
& NO OUTPUT
THEN
CHANGE I501
13
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