Sharp 27C24 Schematic
27C241
SERVICE MANUAL
COLOR TELEVISION
Chassis No. C/D-BM
MODELS
In the interests of user-safety (Required by safety regulations in some countries) the set should be restored to its
original condition and only parts identical to those specified should be used.
27C241
CONTENTS
Page
» ELECTRICAL SPECIFICATIONS .........................................................................................................1
» IMPORTANT SERVICE SAFETY PRECAUTION .................................................................................2
» LOCATION OF USER'S CONTROL .....................................................................................................4
» INSTALLATION AND SERVICE INSTRUCTIONS................................................................................6
» CHASSIS LAYOUT .............................................................................................................................12
» BLOCK DIAGRAM ..............................................................................................................................13
» SCHEMATIC DIAGRAMS ...................................................................................................................14
» PRINTED WIRING BOARD ASSEMBLIES ........................................................................................20
» REPLACEMENT PARTS LIST............................................................................................................23
» PACKING OF THE SET ......................................................................................................................31
ELECTRICAL SPECIFICATIONS
POWER INPUT.................................................... 120 V AC 60 Hz
POWER RATING ..................................................................105 W
PICTURE SIZE ........................................... 2,187cm2 (339sq inch)
CONVERGENCE ............................................................. Magnetic
SWEEP DEFLECTION .................................................... Magnetic
FOCUS ............................................... Hi-Bi-Potential Electrostatic
INTERMEDIATE FREQUENCIES
Picture IF Carrier Frequency ..................................... 45.75 MHz
Sound IF Carrier Frequency...................................... 41.25 MHz
Color Sub-Carrier Frequency .................................... 42.17 MHz
(Nominal)
AUDIO POWER
OUTPUT RATING .....................1.5W + 1.5W (at 10% distortion
and Dual CH Operate)
SPEAKER
SIZE ...............................................................9x5cm (Oval type)
VOICE COIL IMPEDANCE ............................ 32 ohm at 400 Hz
ANTENNA INPUT IMPEDANCE
VHF/UHF.....................................................75 ohm Unbalanced
TUNING RANGES
VHF-Channels...............................................................2 thru 13
UHF-Channels ............................................................14 thru 69
CATV Channels ...........................................................1 thru 125
(EIA, Channel Plan U.S.A.)
Specifications are subject to change without
prior notice.
SHARP CORPORATION
This document has been published to be used for after
sales service only.
The contents are subject to change without notice.
27C241
IMPORTANT SERVICE SAFETY PRECAUTION
Ë
Service work should be performed only by qualified service technicians who are thoroughly
familiar with all safety checks and the servicing guidelines which follow:
WARNING
1. For continued safety, no modification of any circuit
should be attempted.
2. Disconnect AC power before servicing.
3. Semiconductor heat sinks are potential shock
hazards when the chassis is operating.
4. The chassis in this receiver has two ground systems
which are separated by insulating material. The nonisolated (hot) ground system is for the B+ voltage
regulator circuit and the horizontal output circuit. The
isolated ground system is for the low B+ DC voltages
and the secondary circuit of the high voltage
transformer.
To prevent electrical shock use an isolation
transformer between the line cord and power
receptacle, when servicing this chassis.
CAUTION: FOR CONTINUED
PROTECTION AGAINST A
RISK OF FIRE, REPLACE ONL Y
4A 125V
WITH SAME TYPE 4A-125V
FUSE.
SERVICING OF HIGH VOLTAGE SYSTEM
AND PICTURE TUBE
When servicing the high voltage system,
remove the static charge by connecting a
10k ohm resistor in series with an insulated
wire (such as a test probe) between the picture tube ground and the anode lead. (AC
line cord should be disconnected from AC
outlet.)
1. Picture tube in this receiver employs integral implosion
protection.
2. Replace with tube of the same type number for
continued safety .
3. Do not lift picture tube by the neck.
4. Handle the picture tube only when wearing
shatterproof goggles and after discharging the high
voltage anode completely .
X-RADIA TION AND HIGH VOLTAGE LIMITS
1. Be sure all service personnel are aware of the
procedures and instructions covering X-radiation. The
only potential source of X-ray in current solid state
TV receivers is the picture tube. However, the picture
tube does not emit measurable X-Ray radiation, if
the high voltage is as specified in the "High Voltage
Check" instructions.
It is only when high voltage is excessive that Xradiation is capable of penetrating the shell of the
picture tube including the lead in the glass material.
The important precaution is to keep the high voltage
below the maximum level specified.
2. It is essential that servicemen have available at all
times an accurate high voltage meter.
The calibration of this meter should be checked
periodically.
3. High voltage should always be kept at the rated value
−no higher. Operation at higher voltages may cause
a failure of the picture tube or high voltage circuitry
and;also, under certain conditions, may produce
radiation in exceeding of desirable levels.
4. When the high voltage regulator is operating properly
there is no possibility of an X-radiation problem. Every
time a color chassis is serviced, the brightness should
be tested while monitoring the high voltage with a
meter to be certain that the high voltage does not
exceed the specified value and that it is regulating
correctly.
5. Do not use a picture tube other than that specified or
make unrecommended circuit modifications to the
high voltage circuitry.
6. When trouble shooting and taking test measurements
on a receiver with excessive high voltage, avoid being
unnecessarily close to the receiver.
Do not operate the receiver longer than is necessary
to locate the cause of excessive voltage.
2
2
2
IMPORTANT SERVICE SAFETY PRECAUTION
(Continued)
27C241
BEFORE RETURNING THE RECEIVER
(Fire & Shock Hazard)
Before returning the receiver to the user, perform
the following safety checks.
1. Inspect all lead dress to make certain that leads are
not pinched or that hardware is not lodged between
the chassis and other metal parts in the receiver.
2. Inspect all protective devices such as non-metallic
control knobs, insulating materials, cabinet backs,
adjustment and compartment covers or shields,
isolation resistor-capacity networks, mechanical
insulators, etc.
3. To be sure that no shock hazard exists, check for
leakage current in the following manner.
• Plug the AC cord directly into a 120 volt AC outlet,
(Do not use an isolation transformer for this test).
• Using two clip leads, connect a 1.5k ohm, 10 watt
resistor paralleled by a 0.15µF capacitor in series with
all exposed metal cabinet parts and a known earth
ground, such as electrical conduit or electrical ground
connected to earth ground.
• Use an AC voltmeter having with 5000 ohm per volt,
or higher, sensitivity to measure the AC voltage drop
across the resistor.
• Connect the resistor connection to all exposed metal
parts having a return to the chassis (antenna, metal
cabinet, screw heads, knobs and control shafts,
escutcheon, etc.) and measure the AC voltage drop
across the resistor.
AII checks must be repeated with the AC line cord
plug connection reversed. (If necessary, a nonpolarized adapter plug must be used only for the
purpose of completing these check.)
Any current measured must not exceed 0.5 milliamp.
Any measurements not within the limits outlined
above indicate of a potential shock hazard and
corrective action must be taken before returning the
instrument to the customer.
1.5k ohm
10W
0.15µF
TEST PROBE
TO EXPOSED
MET AL PARTS
234567890123456789012345678901212345678901234567890123456789012123456789012345678901234567890121
CONNECT TO
KNOWN EARTH
GROUND
SAFETY NOTICE
Many electrical and mechanical parts in television
receivers have special safety-related characteristics.
These characteristics are often not evident from visual
inspection, nor can protection afforded by them be
necessarily increased by using replacement components
rated for higher voltage, wattage, etc.
Replacement parts which have these special safety
characteristics are identified in this manual; electrical
components having such features are identified by "å"
and shaded areas in the Replacement Parts Lists and
Schematic Diagrams.
234567890123456789012345678901212345678901234567890123456789012123456789012345678901234567890121
For continued protection, replacement parts must be
identical to those used in the original circuit. The use of
substitute replacement parts which do not have the same
safety characteristics as the factory recommended
replacement parts shown in this service manual, may
create shock, fire, X-radiation or other hazards.
3
27C241
Front Panel
POWER
→
Press On.
Press again Off.
→
LOCATION OF USER'S CONTROL
(27C241)
VIDEO IN 2 L-AUDIO-R
(VIDEO/AUDIO terminals are also
provided on the rear.)
SENSOR AREA FOR
REMOTE CONTROL
MENU
→
Press Accesses MAIN
MENU.
Press again Exits MAIN
MENU.
Basic Remote Control Functions
POWER
Press On.
→
Press again Off.
REMOTE KEYPAD
Accesses any channel from keypad.
FLASHBACK
Returns to previous channel.
VOLUME UP/DOWN
(+) Increases sound.
(–) Decreases sound.
• In menu mode, changes or selects
the TV adjustments.
MUTE
Press Mutes sound.
Press again Restores sound.
• CLOSED CAPTION appears when
sound is muted.
→
→
→
→
VOLUME UP/DO WN
(+) Increases sound.
(–) Decreases sound.
CHANNEL UP/DOWN – MENU
\
( ) Selects next higher channel.
( ) Selects next lower channel.
\
• Press both at the same time to
access the MAIN MENU
screen.
Infrared T r ansmitter Window
INPUT
Press Switch to external video
→
INPUT 1 mode.
Press 2 times Switch to external
video INPUT 2 mode.
Press 3 times Switch back to the
original TV mode.
CHANNEL UP/DOWN
\
( ) Selects next higher channel.
( ) Selects next lower channel.
\
• Moves the “
screen.
MENU
→
Press Accesses MAIN MENU.
Press again Exits MAIN MENU.
DISPLAY
→
Press Displays receiving channel f or
four seconds.
Press again Removes display.
• Temporarily displays receiving
channel when in Closed Caption
mode.
→
→
” mark of the MENU
→
→
TV
4
INSTALLATION AND SERVICE INSTRUCTIONS
Note: (1)When performing any adjustments to resistor controls and transformers use non-metallic
screwdrivers or TV alignment tools.
(2)Before performing adjustments, the TV set must be on at least 15 minutes.
27C241
CIRCUIT PROTECTION
The receiver is protected by a 4.0A fuse (F701),
mounted on PWB-A, wired into one side of the AC
line input.
X-RADIA TION PROTECTOR CIRCUIT TEST
After service has been performed on the horizontal
deflection system, high voltage system, B+ system,
test the X-Radiation protection circuit to ascertain
proper operation as follows:
1. Apply 120V AC using a variac transformer for accurate
input voltage.
2. Allow for warm up and adjust all customer controls
for normal picture and sound.
3. Receive a good local channel.
4. Connect a digital voltmeter to TP653 and make sure
that the voltmeter reads 21.9 ±1.4V.
5. Apply external 27.8V DC at TP653 by using an
external DC supply, TV must be shut off.
6. To reset the protector , unplug the AC cord and make
a short circuit between TP651 and TP652. Now make
sure that normal picture appears on the screen.
7. If the operation of the horizontal oscillator does not
stop in step 5, the circuit must be repaired before the
set is returned to the customer.
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 checks
should be as follows:
1. Connect an accurate high voltage meter between
ground and anode of picture tube.
2. Operate receiver for at least 15 minutes at 120V AC
line voltage, with a strong air signal or a properly tuned
in test signal.
3. Enter the service mode and select the service
adjustment "S03" and Bus data "01" (Y-mute on).
4. The voltage should be approximately , 30.5kV (at zero
beam).
If a correct reading cannot be obtained, check circuitry
for malfunctioning components. After the voltage test,
make Y-mute off to the normal mode.
5
Window 2: DEF
DEF
RETURN
RETURN
FIX V ALUE
NEXT
FEATURE
D01
D03
D05
RETURN
D02
D04
D06
Window 5: FIX VALUE
Window 1: ADJUSTMENT CATEGORIES
SERVICE MODE
DEF
SIGNAL
FEATURE
FIX V ALUE
EEPROM
RETURN
RETURN
Window 3: SIGNAL
SIGNAL
S01
S13
RETURN
S02
S14
F01 F02
F13 F14
RETURN NEXT
F15 F16
F27
F26
RETURNPREVIOUS
PREVIOUS
Window 4: FEATURE
M01 M02
M05
M03 M04
RETURN
27C241
For adjustments of this model, the bus data is converted to various analog signals by the D/A converter circuit.
Note: There are still a few analog adjustments in this series such as focus and master screen voltage. Follow
the steps below whenever the service adjusment is required.
To enter the service mode and exit service mode.
While pressing the Vol-up and Ch-up buttons at the sametime, plug the AC cord into a wall socket.
Now, the TV set is switched on and enters the service mode.
To exit the service mode, turn the television off by pressing the power button.
1. Service mode.
Before putting unit into the service mode, check that customer adjustments are in the normal mode. Use the reset
function in the video adjustment menu to ensure customer control are in their proper (reset) position.
2. Service number selection.
In the service mode, you will see the window screen as window 1. There are 4 adjustment categories 2DEF,
3SIGNAL, 4FEATURE, 5FIX VALUE as show in Figure A.
Press CH UP/DOWN button for selection and enter by VOL UP or VOL DOWN.
Press CH UP/DOWN button to select the adjustment item and VOL UP/DOWN
to adjust the data number for each categories.
(OSD disturbance can be erased by R/C display key)
(Note: EEPROM - factory used only)
Figure A: ADJUSTMENT CATEGORIES
6
Below are the adjustments ranges and initial values for FIX V ALUE category.
FIX V ALUE
SERVICE
POSITION
F01 OPTION 1 00-FF B1 *1
F02 OPTION 2 00-FF 07 27
F03 E-SAVE 00-3F 2A 2A
F04 TUNER SETUP 00, 01 00 00
F05 R-TONE RD 00-7F 03 03
F06 R-TONE BD 00-7F 7C 7C
F07 B-TONE RD 00-7F 00 00
F08 B-TONE BD 00-7F 04 04
F09 FM LEVEL 00-1F 16 16
F10 AFC GAIN 00, 01 00 00
F11 G DRIVE 00, 0F 0F 0F
F12 FBT BLK SW 00, 01 01 01
F13 V COMP 00-07 07 07
F14 OSD CONT 00-03 01 01
F15 SHARPNESS 00-3F 0D *2
F16 FLT SYS 00-07 01 01
F17 KILLER OP 00-07 02 02
F18 PRE SHOOT 00-03 00 00
F19 CORING 00-03 04 04
F20 DC REST 00-03 02 02
F21 BS S TART 00-03 01 01
F22 BS GAIN 00-03 01 01
F23 ABL START 00-07 00 00
F24 R/B ANGLE 00-0F 08 08
F25 H BLK R 00-0F 03 03
F26 H BLK L 00-0F 00 00
F27 YC 00-07 05 04
ADJUST ITEM
RANGE
DATA
INITIAL VALUE
27C241
(Hex)
*1: adjust item
ADJUST ITEM
OPTION 1 B1
27C241
MODEL
*2: type of tuner
TUNER TYPE
VTUVT1T5UF202 13
VB68ADT2506*S
CRT
Table - A
Below are the ranges and initial values for each adjustment and in each categories.
DEF
SERVICE
POSITION
D01 H-PHASE 00-1F 0C
D02 V-SIZE 00-7F 40
D03 V-POSITION 00-3F 20 Must be "20"
D04 CC-POSITION 00-FF 1A
D05 V-LINEARITY 00-1F 10 Must be "13"
D06 V-S-CORRECTION 00-1F 10 Must be "14"
ADJUST ITEM
RANGE
DATA
INITIAL VALUE
ADJUSTMENT CONTENTS
Table - B
7
27C241
SIGNAL
SERVICE
POSITION
S01 RF AGC 00-3F 14
S02 VIDEO LEVEL 00-07 03 Must be "4"
S03 Y-MUTE 00-03 00
S04 SUB BIAS 00-FF 30 Must be "30"
S05 R-BIAS 00-FF 00
S06 G-BIAS 00-FF 00
S07 B-BIAS 00-7F 00
S08 R-DRIVE 00-7F 53
S09 B-DRIVE 00-7F 53
S10 CONTRAST 00-7F 5A
S11 TINT 00-7F 40
S12 COLOR 00-7F 40
S13 BRIGHTNESS 00-7F 40
S14 BRIGHTNESS 2 00-7F 40
Note: Refer to the SERVICE ADJUSTMENT for each corresponding values.
ADJUST ITEM
RANGE
DATA
INITIAL VALUE
"01": Y -MUTE, "02": V-STOP & Y-MUTE
"03":
T able - C
FEATURE
SERVICE
POSITION
M01 MS LEVEL 00-0F 0A
ADJUST ITEM
RANGE
DATA
INITIAL VALUE
ADJUSTMENT CONTENTS
Activate color killer circuit.
ADJUSTMENT CONTENTS
M04 LOW SEPARATION 00-3F 20
M05 HIGH SEPARATION 00-3F 1B
Note: Refer to the SERVICE ADJUSTMENT for each corresponding values.
T able - D
Holding down both the Vol-up/Ch-down buttons on the TV set at service mode for more than 2 seconds will
automatically write the above initial values into IC2102.
P ART REPLACED
IC2001
IC201
IC2102
IC3001 X
CRT X
NECESSARY
ADJUSTMENT
X
X
UNNECESSARY
X
NOTES
Data is stored in IC2102.
The adjustment is needed to compensate for characteristics
of parts including IC201.
Holding down both the Vol-up/Ch-down buttons on the TV set
in the service mode for more than 2 seconds will automatically
write the above initial values into IC2102.
Adjust items related MTS only.
Adjust items related to picture tube only.
T able - E
8
Ë
SERVICE ADJUSTMENT
Note: Before making the service adjustment, make the
bus data settings.
+B Adjustment
1. Receive a good local channel.
2. Select VIDEO ADJUSTMENT RESET on the
menu to get the video reset.
3. Connect a DC voltmeter between the +B line (at
SW transformer) of R61 1 and the ground terminal.
4. Make sure that the voltmeter reads 128.5±1.5V.
Video Level (TV Det Video Level)
Adjustment
1. Receive a good local channel.
2. Enter the service mode signal category and select
the service adjustment "S02".
3. Set the data value to "02" first, then adjust the data
to "04". (If out of spec, readjust the data in the range
of "00" to "07" to obtain a normal contrast level.)
RF AGC Adjustment
1. Receive a good local channel.
2. Enter the service mode signal category and select
the service adjustment "S01".
3. Set the data value to point where no noise or beat
appears.
4. Select another channel to confirm that no noise or
beat appears.
Note: You have to exit the service mode first to
select another channel.
Screen Adjustment
1. Connect to oscilloscope probe between TP854 and
ground of the CRT unit.
2. Receive a good local channel.
3. Enter the service mode Signal category and set the
service adjustment "S04" to step 30. Then select the
service adjustment "S12" and set the data value to
"00" to set the color level to the minimum level. (record
the original data first). You may skip this step, if you
selected a B/W picture or monoscope pattern. Set
also the "S05/S06/S07" data to minimum level ("00").
2.35 Vdc
GND
Figure B: WAVEFORM FOR SCREEN ADJUSTMENT
4. Select the service adjustment "S03" and set the data
value to "01" to turn off the luminance signal (Y -mute).
5. Select the service adjustment "S14" and adjust the
data value to obtain 2.35 volts as shown in Figure B.
6. Adjust the master screen control until the raster
darkens to the point where raster is barely seen.
27C241
7. Adjust the service adjustment "S05" red, "S06" green,
"S07" blue to obtain a good grey scale with normal
white at low brightness level.
8. Select the service a adjustment "S03" and reset data
to "00". Select the service adjustment "S12" and reset
data to obtain normal color level.
9. Remove probe and reset the master screen control
to obtain normal brightness range.
White Balance Adjustment
1. Receive a good local channel.
2. Select the service adjustment "S12" and set the data
value to "00" to set the color level to the minimun. Y ou
may skip this step, if you selected a B/W picture or
monoscope.
3. Alternately adjust the service adjustment data of
"S08" and "S09" until a good grey scale with normal
white is obtained.
4. Select the service adjustment "S12" and reset data
to obtain normal color level.
Sub-Picture Adjustment
1. Receive a good local channel.
2. Make sure the customer picture control is set to
maximum.
3. Enter the service mode and select the service
adjustment "S10".
4. Adjust the data value to achieve normal contrast
range.
Sub-Tint Adjustment
1. Receive a good local channel.
2. Set the customer tint control to the center of it’s range.
3. Enter the service mode and select the service
adjustment "S11".
4. Adjust "S1 1" data value to obtain normal fresh tones.
Sub-Color Adjustment
1. Receive a good local channel.
2. Make sure the customer color control is set to center
position.
3. Enter the service mode and select the service
adjustment "S12".
4. Adjust "S12" data value to obtain normal color level.
Sub-Brightness Adjustment
1. Receive a good local channel.
2. Make sure the customer brightness control is set to
center position.
3. Enter the service mode and select the service
adjustment "S13".
4. Adjust "S13" data value to obtain normal brightness
level.
9
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