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

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS
TDA 4605
Control IC for Switched-Mode Power Supplies Using MOS-Transistor
1. Features
Fold-back characterisitics provides overload protection for external
components
Burst operation under secondary short-circuit condition implemented
Protection against open or a short of the control loop
Switch-off if line voltage is too low (undervoltage switch-off)
Line voltage depending compensation of fold-back point
Soft-start for quiet start-up without noise generated by the transformer
Chip-over temperature protection implemented(thermal shutdown)
Fig. 10
On-chip ringing suppression circuit against parasitic oscillations of the
transformer
AGC-voltage reduction at low load
2. Block Diagram
Fig. 11
3. Refer to Table 3 about Functions and Data of the IC’s Each Pin.
8

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
CH04T1002/ CH04T1009
1. Terminal Assignment Layouts
Fig. 12 CH04T1002/ CH04T1009 DIP42S Terminal Assignment Layoutd
Fig. 13 CH04T1002/ CH04T1009 QIP48E Terminal Assignment Layout
9

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
CH04T1002/ CH04T1009 (continued)
2. Terminal Function
Table 2 Terminal Function Table
Terminal I/O Function Description Option Format
VSS - Negative power supply
XT1 1 Input terminal for crystal oscillation
XT2 O Output terminal for crystal oscillation
VDD - Positive power supply
RES I Reset terminal A
FILT O Charge-pump ouput terminal N
CVIN I
Image signal input terminal
(available only in CH04T1002) M
VS I
Vertical synchronization signal input terminal
HS I
Horizontal synchronization signal input terminal A
R O
Red (R) output terminal of RGB image
G O
Green (G) output terminal of RGB image
B O Blue (B) output terminal of RGB imagee
I O Intensity (I) output terminal of RGB image
BL O
Fast blanking control signal
Switch TV image and caption/OSD image signal
O
Part 0
P00-p07
I/O
8-bit input/output port
Input/output can be specified in nibble unit
Other functions:
Hold release input
Internal input
Pull-up resistor
provided/not
provided
Output format
CMOS/Nch-OD
E
Port 1
P10-P17
I/O
8-bit input/output port
Each bit can be independently
programmable
Other functions:
P10 SIO0 data output
P11 SIO0 data input/bus input/output
P12 SIO0 clock input/output
P13 PWM1 output
P14 PWM2 output
P15 PWM3 output
P17 Timer 1(PWM) output
Output format
CMOS/Nch-OD F
Port 6 I/O
4-bit input/output port
Each bit can be independently
programmable
Other functions:
P60 IIC0 data input/output
P61 IIC0 clock output
P62 IIC1 data input/output
P63 IIC1 clock output
10

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
CH04T1002/CH04T1009 (continued)
Terminal I/O Function Description Option Format
Port 7
P71-P73
I/O
4-bit input/output port
Each bit can be independently
programmable
Other functions:
P70 INTO input/HOLD release input
/Nch-Tr. output for watchdog timer
P71 INT1 input/HOLD release input
P72 INT2 input/timer 0 event input
P73 INT3 input (noise rejection filter attached
input)/timer 0 event input
Interrupt receiver format vector address
Rising Falling Rising/
Falling H level L level Vector
INTO
INT1
INT2
INT3
yes
yes
yes
yes
yes
yes
yes
yes
no
no
yes
yes
yes
yes
no
no
yes
yes
no
no
03H
0BH
13H
1BH
P70
W
P71-P73
V
Port 8
P83
P84-P87
I
I/O
1-bit input port
(P83 is set only in CH04T1002)
4-bit input/output port(P84-P87)
Each bit can be independently
programmable
Other function:
AD converter input port
P83
B
P84-P87
X
Port options can be specified independently for each bit.
The programmable pull-up resistors are provided, depending on whether CMOS or Nch-OD (Nch
open drain ) is selected as the port 1 option.
3. Refer to Table 3 about Functions and Data of the IC’s Each Pin.
11

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
EEPROM AT24C04
1. Features 2. Pin Configuration
Data EEPROM internally organized as 512
bytes and 32 pages×16 bytes
Low power CMOS
Vcc=2.7 to 5.5V operation
Two wire serial interface bus I
2C-Bus
compatible
Filtered inputs for noise suppression with
Schmitt trigger
Clock frequency up to 400 kHz
High programming flexibility
-Internal programming voltage
-Self timed programming cycle including erase
-Byte-write and page-write programming
between 1 and 16 bytes
-Typical programming time 6 ms(<10ms) for up
to 16 bytes
High reliability Fig. 14
-Endurance 106cycles1)
-Data retention 40 years1)
-ESD protection 4000 V on all pins 4. Refer to Table 5 about Functions and
Data of the IC’s Each Pin
8 pin DIP/DSO packages
Available for extended temperature ranges
-Industrial -40 to +85
-Automotive -40 to +125
3. Block Diagram
Fig. 15
12

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
OM8839PS/TDA8843-N2
I2C-bus Controlled PAL/NTSC/SECAM TV Processors
1. Features
The following features are available in all IC s:
·Multi-standard vision IF circuit with an
alignment-free PLL demodulator without external
components
·Alignment-free multi-standard FM sound
demodulator (4.5 MHz to 6.5 MHz)
·Audio switch
·Flexible source selection with CVBS switch and
Y(CVBS)/C input so that a comb filter can be
applied
·Integrated chrominance trap circuit
·Integrated luminance delay line
·Asymmetrical peaking in the luminance channel
with a (defeatable) noise coring function
·Black stretching of non-standard CVBS or
lumina-nce signals
·Integrated chroma band-pass filter with
switchable centre frequency
·Dynamic skin tone control circuit
·Blue stretch circuit which offsets colours near
white towards blue
·RGB control circuit with “Continuous Cathode
Calibration” and white point adjustment
·Possibility to insert a“blue back” option when no
video signal is available
·Horizontal synchronization with two control loops
and alignment-free horizontal oscillator
·Vertical count-down circuit
·Vertical driver optimised for DC-coupled vertical
output stages
·I2C-bus control of various functions
2. General Description
The various versions of the TDA 884X/5X
series are I2C-bus controlled single chip TV
processors which are intended to be applied
in PAL, NTSC, PAL/NTSC and multi-standard
television receivers. The N2 version is pin and
application compatible with the N1 version,
however, a new feature has been added
which makes the N2 more attractive. The IF
PLL demodulator has been replaced by an
alignment-free IF PLL demodulator with
inter-nal VCO (no tuned circuit required). The
setting of the various frequencies (33.4,
33.9,38, 38.9, 45, 75 and 58.75 MHz) can be
made via the I2C-bus.
Because of this difference the N2 version is
compatible with the N1, however, N1 devices
cannot be used in an optimised N2
application.
Functionally the IC series is split up in 3
categories, viz:
·Versions intended to be used in economy TV
receivers with all basic functions (envelope:
S-DIP 56 and QFP 64)
·Versions with additional features like E-W
geometry control, H-V zoom function and
YUV interface which are intended for TV
receivers with 110° picture tubes (envelope:
S-DIP 56)
·Versions which have in addition a second
RGB input with saturation control and a
second CVBS output (envelope: QFP 64)
The various type numbers are given in the
table below.
3. Survey of IC Types
Envelope S-DIP 56 QFP 64
TV receiver category Economy Mid/High end Economy Mid/High end
PAL only TDA 8840 TDA 8840H
PAL/NTSC TDA 8841 TDA 8843 TDA 8841H
PAL/SECAM/NTSC TDA 8842 TDA 8844 TDA 8842H TDA 8854H
NTSC only TDA 8846/46A TDA 8847 TDA 8857H
13

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
OM8839PS/TDA8843-N2 (continued)
4. Block Diagram
Fig .16 Block Diagram “Economy Versions” (S-DIP 56 Envelope)
5. Refer to Table 6 about Functions and Data of the IC’s Each Pin.
14

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
TDA8350Q
DC-coupled Vertical Deflection and East-West
Output Circuit
1. Features
Few extemal components
Highly efficient fully DC-coupled vertical output
bridge circuit
Vertical flyback switch
Guard circuit
Protection against
- short-circuit of the output pins
- short-circuit of the output pins to Vp
3.Block Diagram
High EMC immunity due to common mode
inputs
Temperature (thermal) protection
East-West output stage with one single
conversion resistor.
2. General Description
The TDA8350Q is a power circuit for use in
90° and 110° colour deflection systems for
field frequencies of 50 to 120 Hz. The circuit
provides a DC driven vertical deflection output
circuit, operating as a highly efficient class G
system and an East-West driver for sinking the
diode modulator current.
Fig. 17 Block Diagram
4. Refer to Table 7 about Functions and Data of the IC’s Each Pin.
15

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
TDA7057AQ
2×8W Stereo BTL Audio Output Amplifier with DC Volume Control
1. Features
·DC volume control
·Few external components
·Mute mode
·Thermal protection
·Short-circuit proof
·No switch-on and switch-off clicks
·Good overall stability
·Low power consumption
·Low HF radiation
·ESD protected on all pins.
General Description
The TDA7057AQ is a stereo BTL output amplifier with DC
volume control. The device is designed for use in TVs and
monitiors, but is also suitable for battery-fed portable
recorders and radios.
issing Current Limiter (MCL)
A MCL protection circuit is built-in. The MCL circuit is
activated when the difference in current between the output
terminal of each amplifier exceeds 100 mA (typical 300
mA). This level of 100 mA allows for single-ended
headphone applications.
3. Block Diagram
Fig. 18 Block Diagram
4. Refer to Table 8 about Functions and Data of the IC’s Each Pin.
16

SERVICE MANUAL
IC DATA AND WAVEFORMS OF KEY POINTS (continued)
TDA6107Q
Triple Video Output Amplifier
1. Features
·Typical bandwidth of 5.5 MHz for an output
signal of 60 V (p-p)
·High slew rate of 900 V/S
·No external components required
·Very simple application
·Single supply voltage of 200 V
·Internal reference voltage of 2.5 V
·Fixed gain of 50
·Black-Current Stabilization (BCS) circuit
·Thermal protection.
2. General Description
The TDA6107Q includes three video output
amplifiers in one plastic DIL-bent-SIL 9-pin
medium power (DBS9MPF) package (SOT
111-1), using high-voltage DMOS technology,
and is intended to drive the three cathodes of a
colour CRT directly. To obtain maximum
performance, the amplifier should be used with
black-current control.
3. Ordering Information
Package
Type
Number Name Description Version
TDA6107Q DBS9MPF
Plastic DIL-bent-SIL medium power package with fin; 9
leads SOT111-1
4. Block Diagram
Fig. 19 Block Diagram (One Amplifier Shown)
5. Refer to Table 9 about Functions and Data of the IC’s Each Pin.
17