Apex Digital AT2408S, AT2708S User manual

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SERVICE MANUAL
FILE NO. SM-CTV-O-044
COLOR TELEVISION
SERVICE MANUAL
MODEL NO. AT2408S/AT2408
CHASSIS NO. CH-10C1(S)
Please read this manual carefully before service
PRINTED IN CHINA.MAY.2003 ©

SERVICE MANUAL
CONTENTS
SAFETY INSTRUCTIONS...........................................................................................1
SPECIFICATIONS.......................................................................................................2
KDEY ICS AND ASSEMBLIES....................................................................................3
SYSTEM BLOCK DIAGRAMS.....................................................................................4
IC DATA AND WAVEFORMS OF KEY POINTS ..........................................................5
CIRCUIT ADJUSTMENTS...........................................................................................5
SET-UP ADJUSTMENTS ............................................................................................5
SERVICE MODE AND BUS DATA ..............................................................................5
TROUBLESHOOTING FLOW CHARTS......................................................................7
SERVICE SPARE PARTS LIST.................................................................................13
APPENDIX
1. CIRCUIT DIAGRAM
2. FINAL WIRING DIAGRAM
3. FINAL ASSEMBLY DIAGRAM
4. PRINTED CIRCUIT BOARD DIAGRAMS

SERVICE MANUAL
SAFETY INSTRUCTIONS
WARNING: BEFORE SERVICING THIS CHASSIS, READ THE “X-RAY
RADIATION PRECAUTION”, “SAFETY PRECAUTION” AND “PRODUCT
SAFETY NOTICE” INSTRUCTION BELOW.
X-RAY RADIATION PRECAUTION
1. The EHT must be checked every time the TV is serviced to ensure that the CRT does not emit X-ray
radiation as result of excessive EHT voltage. The nominal EHT for this TV is 27.5KV at zero beam
current (minimum brightness) operating at AC 120V. The maximum EHT voltage permissible in any
operating circumstances must not exceed 30KV. When checking the EHT, use the High Voltage
Check procedure in this manual using an accurate EHT voltmeter.
2. The only source of X-RAY in this TV is the CRT. To prevent X-ray radiation, the replacement CRT
must be identical to the original fitted as specified in the parts list.
3. Some components used in this TV have safety related characteristics preventing the CRT from
emitting X-ray radiation. For continued safety, replacement component should be made after
referring the PRODUCT SAFETY NOTICE below.
SAFETY PRECAUTION
1. The TV has a nominal working EHT voltage of 27.5KV. Extreme caution should be exercised when
working on the TV with the back removed.
1) Do not attempt to service this TV if you are not conversant with the precautions and procedures for
working on high voltage equipment.
2) When handling or working on the CRT, always discharge the anode to the TV chassis before
removing the anode cap in case of electric shock.
3) The CRT, if broken, will violently expel glass fragments. Use shatterproof goggles and take extreme
care while handling.
4) Do not hold the CRT by the neck as this is a very dangerous practice.
2. It is essential that to maintain the safety of the customer all power cord forms be replaced exactly as
supplied from factory.
3. Voltage exists between the hot and cold ground when the TV is in operation. Install a suitable
isolating transformer of beyond rated overall power when servicing or connecting any test
equipment for the sake of safety.
4. Replace blown fuses within the TV with the fuse specified in the parts list.
5. When replacing wires or components to terminals or tags, wind the leads around the terminal before
soldering. When replacing safety components identified by the international hazard symbols in the
circuit diagram and parts list, it must be the company-approved type and must be mounted as the
original.
6. Keep wires away from high temperature components.
1

SERVICE MANUAL
SAFETY INSTRUCTIONS (continued)
PRODUCT SAFETY NOTICE
Many electrical and mechanical components in this chassis have special safety-related characteristics.
These characteristics are often passed unnoticed by a visual inspection and the X-ray radiation
protection afforded by them cannot necessarily be obtained by using replacements rated at higher
voltages or wattage, etc. Components which have these special safety characteristics in this manual
and its supplements are identified by the international hazard symbols in the circuit diagram and parts
list. Before replacing any of these components read the parts list in this manual carefully. Substitute
replacement components which do not have the same safety characteristics as specified in the parts
list may create X-ray radiation.
PRECAUTIONS
Alternate Warnings-A three wire grounding type
plug-a plug having a third (grounding) pin. This
plug will only fit into grounding type powe
r
outlet.
Water and Moisture Warnings-Do not use the
TV set near water-for example, near a bath tub,
wash bowl, kitchen sink, or laundry tub; in a wet
basement; or near a swimming pool; and the
like.The TV set shall not be exposed to dripping
or splashing and no objects filled with liquids,
such as vases, shall be placed on the TV set.
Ventilation-Slots and openings in the cabinet are
provided for ventilation and to ensure reliable
operation of the TV set and to protect it from
overheating, and these openings must not be
blocked or covered. The openings should neve
r
be blocked by placing the TV set on a bed, sofa,
rug, or other similar surface. This TV set should
not be placed in a built-in installation such as a
bookcase or rack unless proper ventilation is
provided or the manufacturer s instructions
have been adhered to.
Power Sources-The TV set should be operated
only from the type of power source indicated on
the TV set or as indicated in the Service
Manual. If you are not sure of the type of powe
r
supply in your home, consult your sales person
or your local power company. For TV sets
designed to operate from battery power, or othe
r
sources, refer to the operating instructions.
Grounding or Polarization-Do not defeat the
safety purpose of the polarized o
r
grounding-type plug. A polarized plug has two
blades with one wider than the other.
A
grounding-type plug has two blades and a third
grounding prong. The wide blade or the third
prong is provided for your safety. If the provided
plug does not fit into your outlet, consult an
electrician for replacement of the obsolete
outlet.
Wide blade
Lame large
Cuchilla ancha
2

SERVICE MANUAL
SPECIFICATIONS
Television system: NTSC-M
VHF 2 13
UHF 14 69
CABLE TV: MID BAND (A-8 A-1, A I)
SUPERBAND(J W)
HYPER BAND (AA ZZ, AAA, BBB)
ULTRABAND(65 94, 100 125)
181
75 (unbalanced)
Effective screen dimensions: 478mm×363mm (18.82×14.29 in.)
5W×2 (for AT2408 only); 5W+5W (for AT2408S only)
120Vac 60Hz
31.5kg (69 lbs) (Approx.)
660×522×458mm (25.98×20.55×18.03 in.) (Approx.)
740×610×545mm (29.13×24.02×21.46 in.) (Approx.)
125W
Channel coverage:
Channels preset:
Antenna input:
Picture tube;
Max. audio output;
Power source;
Weight:
Dimensions(W/H/D):
Packing dimensions(W/H/D):
Rated power consumption:
Designs and specifications are subject to change without notice.
KEY ICS AND ASSEMBLIES
Table 1 Key ICs and Assemblies
Serial No. Position No. Model No. Function Description
1 N301 OM8839PS/TDA8843-N2 Small signal processor
2 N401 TDA8350Q Vertical output circuit
3 N402 LM317 Tri-terminal regulator
4 N601 TDA7057AQ Sound power amplifier
5 N001 CH04T1002/CH04T1009 Microcontroller
6 N002 AT24C04 EEPROM
7 N811 TDA4605 Switching power control circuit
8 NY01 TDA6107Q Video amplifier
9 DS01 HEF4052 Analog switch circuit
10 DS02 HEF4053 Analog switch circuit
11 N606 TDA9859 Audio processor
12 U101 TDQ-6F2M2 Tuner
Note: TDA9859 (N606) is not available in AT2408.
3

SERVICE MANUAL
SYSTEM BLOCK DIAGRAMS
Fig.1 Block Diagram for CH-10C1(S) Remote Control Structur
4

SERVICE MANUAL
SYSTEM BLOCK DIAGRAMS(continued)
Fig. 2 Structure Block Diagram for CH-10C1(S) Chassis
5

SERVICE MANUAL
SYSTEM BLOCK DIAGRAMS(continued)
Fig. 3 Block Diagram for CH-10C1(S) Supply Voltage System
6

SERVICE MANUAL
SYSTEM BLOCK DIAGRAMS(continued)
Fig. 4 Block Diagram for CH-10C1(S) Video Signal Processor
7