In the interests of user-safety (Required by saf ety regulations in some countries ) the set should be restored to its
original condition and only parts identical to those specified should be used.
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.
21FL94
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.
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-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. 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
3
3
IMPORTANT SERVICE SAFETY PRECAUTION
DVM
AC SCALE
1.5k ohm
10W
TO EXPOSED
METAL PARTS
CONNECT TO
KNOWN EARTH
GROUND
2
2
(Continued)
21FL94
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 110~220 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 ha ving with 5000 ohm per volt,
or higher, sensitivity to measure the A C v oltage 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.
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.
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
21FL94
LOCATION OF USER'S CONTROL
4
21FL94
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.
CIRCUIT PROTECTION
The receiver is protected by a 3.15A fuse (F701),
mounted on PWB-A, wired into one side of the AC
line input.
X-RADIATION 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 110~220V 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 P603 pin3 and make
sure that the voltmeter reads 20 ±1.1V.
5. Apply external 27V DC at P603 pin3 by using an
external DC supply, TV must be shut off.
6. To reset the protector, unplug the AC cord and mak e
a short circuit between P603 pin1 and P603 pin2.
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 110~220V
AC line voltage, with a strong air signal or a properly
tuned in test signal.
3. Enter the service mode and set Y-mute ON by using
Service R/C.
4. The voltage should be approximately 28.7kV (at zero
beam).
If a correct reading cannot be obtained, check circuitry
for malfunctioning components. After the v oltage test,
make Y-mute off to the normal mode.
5
21FL94
SERVICE MODE
Service Mode Overview
1. Service mode is entered by SERVICE key input or CH-UP +VOL-DOWN input during reset.
2. Service mode is cleared by entering SERVICE key command during service mode.
3. If key input port (SERVICE) input is LOW, then it is in service mode.
4. During key input port (SERVICE) input is LOW, clearing service mode by key input SERVICE is disabled.
5. Service mode can be switched to 4 modes as follows by key input MENU;
Adjustment mode
Setting mode
Check mode
Option mode
6. AFT processing is disabled during service mode. PLL setting data is set to fo data.
7. All user data are set to default during service mode. FAO and SPEAKER user settings are off and on respectively
in service mode. Energy Save is off.
8. Sleep timer, View timer, on timer and off timer are inactivated in Service mode.
9. Sound is muting in service mode except at Adjustment Items V20, M01, M03, M04, M05, and M06.
First mode of service mode when SERVICE key is
pressed.
First mode of service mode when local key
CH-UP + VOL-DOWN is pressed after MCU reset.
Micron mask version, software version and ROM correction function status are displayed in check mode.
11
21FL94
ADJUSTMENT METHOD
Caution:to get into the service mode, one of the ways is press direct key for service items. the other ways
is short the main chassis JA301 and JA410
There is three stage of Service Mode data
First stage data from V01 ~ M06
to go into second stage of service mode data, press MENU key
Second stage data from F01 ~ F70
to go into third stage of service mode data, press MENU key
Third stage data from 001 ~ 030
Below is the contents of these data
First Stage