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COLOR MONITOR
SyncMaster 753DF (DF17K*)
SyncMaster 755DF (DF17J*)




SERVICE Manual

COLOR MONITOR CONTENTS
1. Precautions

2. Product Specifications

3. Disassembly & Reassembly

4. Alignment & Adjustments

5. Troubleshooting

6. Exploded View & Parts List

7. Electrical Parts List

8. Block Diagram

9. Wiring Diagram

10. Schematic Diagrams
Samsung Electronics Co., Ltd. May 2000
Printed in Korea
P/N : BH68-00129G-01
1 Precautions
1-1 Safety Precautions
WARNINGS 2. Inspect all protective devices such as nonmetallic
1. For continued safety, do not attempt to modify the control knobs, insulating materials, cabinet backs,
circuit board. adjustment and compartment covers or shields,
2. Disconnect the AC power before servicing. isolation resistor-capacitor networks, mechanical
insulators, etc.
3. When the chassis is operating, semiconductor
heatsinks are potential shock hazards. 3. Leakage Current Hot Check (Figure 1-1):
WARNING: Do not use an isolation transformer during
1-1-1 Servicing the High Voltage VR this test.
and CRT : Use a leakage current tester or a metering system
that complies with American National Standards
WARNING:A high voltage VR replaced in the wrong
Institute (ANSI C101.1, Leakage Current for
direction may cause excessive X-ray
emissions. Appliances), and Underwriters Laboratories (UL
Publication UL1410, 59.7).
Caution: When replacing the high voltage
adjustment VR, it must be fixed by a 4. With the unit completely reassembled, plug the AC
soldering iron after it is properly set. line cord directly into a 120V AC outlet. With the
unit's AC switch first in the ON position and then
1. When servicing the high voltage system, remove OFF, measure the current between a known earth
the static charge by connecting a 10 kohm resistor ground (metal water pipe, conduit, etc.) and all
in series with an insulated wire (such as a test exposed metal parts, including: metal cabinets,
probe) between the chassis and the anode lead. screwheads and control shafts. The current
2. If the HV VR requires adjustment, (a) Replace the measured should not exceed 0.5 milliamp. Reverse
VR and adjust the high voltage to the specification. the power-plug prongs in the AC outlet and repeat
(b) Use a soldering iron to melt the adjustment cap the test.
on the HV VR to prevent any movement.
(READING SHOULD
3. When troubleshooting a monitor with excessively NOT BE ABOVE 0.5mA)

HV, avoid being unnecessarily close to the monitor.
Do not operate the monitor for longer than is LEAKAGE
DEVICE
necessary to locate the cause of excessive voltage. UNDER
CURRENT
TESTER
TEST
4. High voltage should always be kept at the rated TEST ALL
EXPOSED METAL
value, no higher. Only when high voltage is SURFACES

excessive are X-rays capable of penetrating the shell
2-WIRE CORD
of the CRT, including the lead in glass material.
Operation at high voltages may also cause failure of
the CRT or high voltage circuitry. ALSO TEST WITH
PLUG REVERSED
5. When the HV regulator is operating properly, there (USING AC ADAPTER
PLUG AS REQUIRED) EARTH
is no possibility of an X-ray problem. Make sure the GROUND

HV does not exceed its specified value and that it is
regulating correctly. Figure 1-1. Leakage Current Test Circuit
6. The CRT is especially designed to prohibit 1-1-4 Product Safety Notices
X-ray emissions. To ensure continued X-ray
Some electrical and mechanical parts have special
protection, replace the CRT only with one that is
safety-related characteristics which are often not
the same or equivalent type as the original.
evident from visual inspection. The protection they give
7. Handle the CRT only when wearing shatterproof may not be obtained by replacing them with
goggles and after completely discharging the high components rated for higher voltage, wattage, etc. Parts
voltage anode. that have special safety characteristics are identified by
8. Do not lift the CRT by the neck. ! on schematics and parts lists. A substitute
replacement that does not have the same safety
1-1-2 Fire and Shock Hazard : characteristics as the recommended replacement part
Before returning the monitor to the user, perform the might create shock, fire and / or other hazards. Product
following safety checks: safety is under review continuously and new
1. Inspect each lead dress to make certain that the instructions are issued whenever appropriate.
leads are not pinched or that hardware is not Components identified by on schematics and parts
lodged between the chassis and other metal parts in lists must be sealed by a soldering iron after
the monitor. replacement and adjustment.



SyncMaster 753DF/755DF 1-1
1 Precautions

1-2 Servicing Precautions
WARNING1: First read the "Safety Precautions" section of this manual. If unforeseen circumstances
create conflict between the servicing precautions and safety precautions, always
follow the safety precautions.

WARNING2: A high voltage VR replaced in the wrong direction may cause excessive X-ray
emissions.

WARNING3: An electrolytic capacitor installed with the wrong polarity might explode.

1. Servicing precautions are printed on the cabinet, 5. Check the insulation between the blades of the AC
and should be followed closely. plug and accessible conductive parts (examples:
2. Always unplug the unit's AC power cord from the metal panels, input terminals and earphone jacks).
AC power source before attempting to: (a) remove 6. Insulation Checking Procedure: Disconnect the
or reinstall any component or assembly, (b) power cord from the AC source and turn the power
disconnect PCB plugs or connectors, (c) connect all switch ON. Connect an insulation resistance meter
test components in parallel with an electrolytic (500 V) to the blades of the AC plug.
capacitor. The insulation resistance between each blade of the
3. Some components are raised above the printed AC plug and accessible conductive parts (see
circuit board for safety. An insulation tube or tape above) should be greater than 1 megohm.
is sometimes used. The internal wiring is 7. Never defeat any of the +B voltage interlocks. Do
sometimes clamped to prevent contact with not apply AC power to the unit (or any of its
thermally hot components. Reinstall all such assemblies) unless all solid-state heat sinks are
elements to their original position. correctly installed.
4. After servicing, always check that the screws, 8. Always connect a test instrument's ground lead to
components and wiring have been correctly the instrument chassis ground before connecting the
reinstalled. Make sure that the area around the positive lead; always remove the instrument's
serviced part has not been damaged. ground lead last.


1-3 Electrostatically Sensitive Devices (ESD) Precautions
Some semiconductor (solid state) devices can be easily damaged by static electricity. Such components are commonly
called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated circuits and some field-
effect transistors. The following techniques will reduce the incidence of component damage caused by static electricity.


1. Immediately before handling any semiconductor 6. Do not remove a replacement ESD from its
components or assemblies, drain the electrostatic protective package until you are ready to install it.
charge from your body by touching a known earth Most replacement ESDs are packaged with leads
ground. Alternatively, wear a discharging wrist- that are electrically shorted together by conductive
strap device. To avoid a shock hazard, be sure to foam, aluminum foil or other conductive materials.
remove the wrist strap before applying power to 7. Immediately before removing the protective
the monitor. material from the leads of a replacement ESD,
2. After removing an ESD-equipped assembly, place it touch the protective material to the chassis or
on a conductive surface such as aluminum foil to circuit assembly into which the device will be
prevent accumulation of an electrostatic charge. installed.
3. Do not use freon-propelled chemicals. These can Caution: Be sure no power is applied to the
generate electrical charges sufficient to damage chassis or circuit and observe all
ESDs. other safety precautions.
4. Use only a grounded-tip soldering iron to solder or
8. Minimize body motions when handling
desolder ESDs.
unpackaged replacement ESDs. Motions such as
5. Use only an anti-static solder removal device. Some brushing clothes together, or lifting your foot from
solder removal devices not classified as "anti-static" a carpeted floor can generate enough static
can generate electrical charges sufficient to damage electricity to damage an ESD.
ESDs.
9. Indicates ESDs on the Schematic Diagram in
this manual.


1-2 SyncMaster 753DF/755DF
2 Product Specifications
2-1 Specifications
Item Description

Picture Tube: 17-Inch (43 cm): 16-inch (40.6 cm) viewable,
Flat-face, 90