SHARP 25MR15J Service Manual
25MR15J
SERVICE MANUAL
S21Q225MR15J/
COLOR TELEVISION
Chassis No. SN-70A
MODEL
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.
25MR15J
CONTENTS
Page
» ELECTRICAL SPECIFICATIONS.........................................................................................................1
» IMPORTANT SERVICE SAFETY PRECAUTION.................................................................................2
» SERVICE INSTRUCTIONS..................................................................................................................4
» CHASSIS LAYOUT .............................................................................................................................10
» BLOCK DIAGRAM..............................................................................................................................11
» SCHEMATIC DIAGRAMS...................................................................................................................12
» PRINTED WIRING BOARD ASSEMBLIES........................................................................................18
» REPLACEMENT PARTS LIST............................................................................................................21
» PACKING OF THE SET......................................................................................................................27
ELECTRICAL SPECIFICATIONS
POWER INPUT ....................................................120 V AC 60 Hz
POWER RATING ................................................................... 92 W
PICTURE SIZE ................................................. Approx. 267 sq. in.
CONVERGENCE............................................................. Magnetic
SWEEP DEFLECTION.................................................... Magnetic
FOCUS ....................................................................Hi-Bi-potential
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................................................ 1.5 W + 1.5 W
(at 10% Distortion and Dual CH Operate)
SPEAKER
SIZE ......................................................................8 cm (Round)
VOICE COIL IMPEDANCE............................32 ohm at 400 Hz
ANTENNA INPUT IMPEDANCE
VHF/UHF ................................................... 75 ohm Unbalanced
TUNING RANGES
All 12 television channels ............................ 54 MHz to 88 MHz
174 MHz to 214 MHz
Any of 56 UHF channels.......................... 470 MHz to 806 MHz
CATV Channels (1.14 thru 125) ........ 72. 120 MHz to 804 MHz
Specifications are subject to change without
prior notice.
SHARP CORPORATION
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25MR15J
IMPORTANT SERVICE SAFETY PRECAUTION
Ë
Service work should be performed only b y qualified service technicians who are throughly
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 v oltages
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.
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 A C 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-RADIATION 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. Howe ver , 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 ser vicemen 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 excessiv e high voltage, av oid 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
1.5k ohm
10W
0.15µF
TEST PROBE
CONNECT TO
KNOWN EARTH
GROUND
TO EXPOSED
METAL PARTS
AC
VOLTMETER
(Continued)
25MR15J
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 and 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 0.15mF 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 ha ving with 5000 ohm per volt,
or higher, sensitivity to measure the A C 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 and 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 bef ore returning the
instrument to the customer.
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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 "S"
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.
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25MR15J
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.
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.
CAUTION: FOR CONTINUED
PROTECTION AGAINST A
RISK OF FIRE, REPLACE
4A 125V
ONLY WITH SAME TYPE 4A125V FUSE.
HIGH VOLT A GE 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 "S19" and Bus data "01" (Y-mute on).
4. The voltage should be approximately, 27.1kV (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.
X-RADIATION PROTECT OR CIRCUIT TEST
After service has been performed on the horizontal
deflection system, high volta ge system, +B system,
test the X-Radiation protection circuit to ascertain
proper operation as follows:
1. Apply 120V AC using a variac transformer for accur ate
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 11.2 ± 0.7V.
5. Apply external 14.4V 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. No w 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.
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25MR15J
SERVICE INSTRUCTIONS
For adjustments of this model, the bus data is conver ted 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 adjustment is required. See "Table-B" to determine, if service adjustments are required.
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 controls are in their proper (reset)
position.
2. SERVICE NUMBER SELECTION
Once in the service mode, press the Ch-up or Chdown button on the remote controller or at the set.
The service adjustment number will vary in
increments of one, from "S01" to "M05". Select the item
you wish to adjust.
3. DATA NUMBER SELECTION
Press the Vol-up or down button to adjust the data
number.
DATA NUMBER
SERVICE ADJUSTMENT NUMBER
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.
CHANNEL
S01
Figure 1.
55(085)
02
S01 D:00
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25MR15J
SERVICE INSTRUCTIONS
SERVICE
NUMBER
S01 PICTURE 55 00-7F
S02 TINT 46 00-7F
S03 COLOR 32 00-7F
S04 BRIGHTNESS 40 00-7F
S05 SHARPNESS 28 00-3F Must be set to "28"
S06 VERTICAL PHASE 00 00-07 Must be set to "00"
S07 HORIZONTAL PHASE 12 00-1F
S08 RF-AGC 23 00-3F
S09 VERTICAL AMP 20 00-3F
S10 PIF VCO 2C 00-7F
S11 R CUT-OFF 00 00-FF
S12 G CUT -OFF 00 00-FF
S13 B CUT-OFF 00 00-FF
S14 G GAIN 7F 00-FF
S15 B GAIN 7F 00-FF
S16 TRAP 00 00 or 01 Must be set to "00"
S17 BALANCE 20 00-3F Must be set to "20"
S18 C.C.POSITION 17 00-7F
S19 MUTE 00 00,01,03 "00"=Normal, "01"=No Y, "03"=No Vertical
S20 ENERGY SAVE OFFSET 20 00-3F Must be set to "23"
S21 TIMER 7A 00-1F Must be set to "7A"
S22 OSD SETUP 00 00-03
S23 TUNER SETUP 00 00, 01 Must be set to "00"
OP1
OP2
M01 INPUT LEVEL 0A 00-0F
M02 ST VCO 20 00-3F
M03 FILTER 1C 00-3F
M04 WIDE BAND 20 00-3F
M05 SPECTRAL 1B 00-3F
ADJUSTMENT ITEM
INITIAL V ALUE
OPTION 1 (Set to each model)
OPTION 2 (Set to each model)
DA T A
RANGE
00 00-FF
00 00-FF
ADJUSTMENT CONTENTS
Must be set to "13"
Must be set to "17"
Table - A
Holding down both the Ch-up/down buttons on the TV set at service mode for more than 2 seconds will automatically
write the above initial values into IC2101.
PART REPLACED
NECESSARY
IC2001
IC201
IC2101
CRT X
IC3001
ADJUSTMENT
X
X
X
UNNECESSARY
X
Data is stored in IC2101.
The adjustment is needed to compensate for characteristics
of parts including IC201 and MTS level (M01).
Holding down both the Ch-up/down buttons on the TV set in
the service mode for more than 2 seconds will automatically
write the above initial values into IC2101. Then perform a
complete adjustment.
Adjust items related to picture tube only.
Adjust items related to MTS only (M01~M05).
NOTES
Table - B
6
Ë
SERVICE ADJUSTMENT
25MR15J
SERVICE INSTRUCTIONS
Note: Before making the service adjustment, make he
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 vetween the +B line (at SW
transformer) of R61 and the ground terminal.
4. Adjust R738 so that the voltmeter should read 130 ±
0.5V.
VCO ADJUSTMENT
1. Connect a digital voltmeter between pin (44) of IC201
and GND.
2. Receive a good local channel.
3. Enter the service mode and select the service
adjustment "S10".
4. Adjust the data so that digital voltmeter reads 2.2V.
5. Adjustment is completed, remove the voltmeter , return
to the "normal" mode.
RF AGC ADJUSTMENT
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustment "S08".
3. Set the data value to point where no noise or beat
appears.
4. Select another channel to confir m that no noise or
beat appears.
Note 1: You will have to come out of the service
mode to select another channel.
Note 2: Setting the data to "00" will produce a black
raster.
SCREEN ADJUSTMENT
1. Connect a oscilloscope between TP854 and GND on
the CRT Unit.
2. Receive a good local channel.
3. Enter the service mode and select the service
adjustment "S03" and set the data value to "00" to
set the color level to minimum. (Record original data
code under adjustment "S03" before changing) You
may skip this step, if you selected a B/W picture or
monoscope pattern.
4. Select the ser vice adjustment "S19" and adjust the
data value to "01", this turn off the luminance signal
(Y-mute).
5. Select the service adjustment "S04" and adjust data
value to obtain 2.35V on the oscilloscope screen
(Refer to Figure 2.).
6. Adjust the master screen control until the raster
darkens to the point where raster is barely seen.
7. Adjust the service adjustments "S11" red, "S12" green
and "S13" blue to obtain a good grey scale with normal
whites at low brightness level.
8. Select the ser vice adjustment "S19" and reset data
to "00". Select the service adjustment "S03" and reset
data to obtain normal color level.
9. Remove a oscilloscope, and reset the master screen
control to obtain normal brightness range.
WHITE BALANCE ADJUSTMENT
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustment "S03" and set to "00" (minimum
color)(Record original data code under adjustment
"S03" before changing). "S03" does not have to be
adjusted, if you selected a B/W picture or monoscope
pattern.
3. Alternately adjust the ser vice adjustment data of
"S14" and "S15" until a good grey scale with normal
whites is obtained.
4. Select the service adjustment "S03" and adjust 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 "S01".
4. Adjust the data value to achieve normal contrast
range.
SUB-TINT ADJUSTMENT
1. Receive a good local channel.
2. Set customer tint control to center of it's range.
3. Enter the service mode and select the service
adjustment "S02".
4. Adjust "S02" data value to obtain normal flesh tones.
2.35V
Figure 2.
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 "S03".
4. Adjust "S03" data value to obtain normal color level.
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25MR15J
SERVICE INSTRUCTIONS
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 "S04".
4. Adjust "S04" data value to obtain normal brightness
level.
VERTICAL-SIZE ADJUSTMENT
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustment "S09".
3. While obser ving the top and bottom of the screen,
adjust "S09" data value to proper vertical size.
VERTICAL PHASE ADJUSTMENT
1. Enter the service mode and select the service
adjustment "S06".
2. Adjust data value to "00".
Note: This must be set "00" when changed data
retrace line will appear.
HORIZONTAL POSITION ADJUSTMENT
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustment "S07".
3. Adjust "S07" data value so that picture is centered.
CAPTION POSITION ADJUSTMENT
(Horizontal)
3.58MHz TRAP ADJUSTMENT
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustment "S16".
3. This is a two position adjustment, "00" is ON, "01" is
OFF.
4. Adjust data value to "00" for normal viewing.
SHARPNESS AND AUDIO BALANCE
ADJUSTMENT
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustments "S05" for sharpness and "S17" for audio
balance.
» Sharpness adjustment
3. Adjust data value to "28" (center of data range) for
sharpness adjustment.
» Audio balance adjustment
4. Adjust data value to "20" (center of data range) for
audio balance adjustment.
OTHER ADJUSTMENT
1. Enter the service mode.
2. Adjust the following data values as listed below.
S16 "00" TRAP
S20 "23" ENERGY SAVE OFFSET
S21 "7A" TIMER
S23 "00" TUNER SETUP
1. Receive a good local channel.
2. Enter the service mode and select the service
adjustment "S18".
3. A black text box appears on the screen. (Refer to
Figure 3.)
4. Adjust "S18" data value so that text box is positioned
in the center of the screen.
Figure 3.
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