Xoceco TA2933 Schematic
SERVICE SERVICE
MANUALMANUAL
Contents
Safety Instruction………………………………………………………………………………1
X-ray radiation protection……………………………………………………………………..1
Safety Measures…………
Points of attention for product safety………………………………………………………………3
…………………………………………………………………………..2
Alignment procedures………………………………………………………………………4
Adjustment equipment……………………………………………………………………..5
Adjustment instruction…………………………………………………………………………5
Factory adjustment method………………………………………………………………………..5
IF amplification adjustment…………………………………………………………………….5
B+ confirmation
AGC adjustment…
Sound detection…………………………………………………………………………………….6
Adjustment of Focus Potentiometer……………………………………………………………….6
Alignment of line certer…
Field amplitude, field S alignment, field center, line amplitude, E/W alignment etc. ……………6
Adjustment of screen-grid VG2……………………………………………………………………….7
White balance adjustment…………
Inspection of the high voltage and filament voltage………………………………………………….7
Inspection of X-ray protection………………………………………………………………….7
…………………………………………………………………………………….5
………………………………………………………………………………..5
………………………………………………………………………..6
…………………………………………………………..7
Inspection of beam current…………………………………………………………………..7
Inspection of AV function……………………………………………………………………………….7
Wiring diagram…………………………………………………………………………….8
IC block diagram…………………………………………………………………………..9
Schematic diagram…………………………………………………………………………….11
Electrical parts list ……………………………………………………………………………..13
Assembly drawing of complete set …………………………………………………………34
Detail list of Assembly drawings……………………………………………………………
35
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Attention: This maintenance manual is only intended for the professional maintenance
personnel to take reference with. Before repairing TV set please carefully read
the following points of attention.
Safety Instruction
Before fixing and aligning this set, please read the following “Points of attention for
Safety “, “Points of attention for Safety of Components” and “X-ray Radiation
Protection“.
Points of attention for Safety
1. Because the city power is connected directly to the hot earth of power supply PCB, in order to
avoid electric shock or damage to instruments, an isolate transformer must be applied during the
fixing procedure.
2. Before moving the CRT, graphite layer conductor must be discharged.
3. Before replacing any components, the power plug must be taken out from the power supply
socket.
4. Before replacing large power resistor, 10mm high must be kept between resistor and PCB.
Points of attention for the components safety
There are many electric and mechanical components on the PCB that are related with the
safety features. These features are not easily visible. Replacement parts that have special safety
characteristic are indicated in the Instruction Manual. Electric components with such features will be
labeled with shadow or labeled with in the detail list. When changing these components, please
refer to the detail list in the manual. Components that have different specification from that in the
detail list may not have the same safety features. They may cause electric shock, fire, increase of
X-ray radiation or other damage.
1. Safety instruction
Before fixing or aligning this set, please read the following “ X-ray radiation protection”, “Safety
measures” and “Points of attention for products”.
1.1 X-ray radiation protection
1.1.1 Too high voltage will produce radiation harmful to human health. To avoid such risk, the
high voltage should be regulated within the limited value. For 25”, the normal value of beam
current should be 26.5 kV at 1.3 mA, for 29”, 29kV at1.4 mA and for 29” pure flat TV set,
30kV.
Under any circumstances, the high voltage should not exceed 31kV (25”), 33 kV (29”), 35kV
1
(29” pure flat). When the TV set needs to be fixed, please follow the inspection procedures of
high voltage in item 4.11 under this instruction ”Inspection of high voltage”. It is suggested that
the value of high voltage be recorded as part of maintenance work. It is most essential at the
same time to use precise and dependable high voltage meter.
1.1.2 This set is equipped with X-ray over radiation (FS) protection circuit to prevent over radiation
of X-ray in the case of abnormal increase of B+ voltage in the set. Whenever fixing the set,
FS circuit must be checked according to the inspection procedures as in item 4.11.5 of this
instruction, ”X-ray radiation protection test” to make sure the circuit functions well.
1.1.3 The only source of TV set producing X-ray is CRT. To avoid X-ray radiation during the whole
process, the exact same type of CRT designated in the detail list must be replaced, when
there is a need to change CRT.
1.1.4 When deciding on the same type of 4, as some components of this TV set are related to the
safety characteristic, please read the “Points of attention for products safety” before changing
the components, for the sake of safety.
1.2 Safety measures
1.2.1 When the TV set is working, the high voltage will be as high as approximately 31kV. When
adjusting the set after removing the cover or opening the back cabinet there will be risk of
electric shock, so
a) Before detaching the anode cap, please discharge it several times by grounding the anode
of CRT to earth many times to avoid electric shock.
b) Before moving the CRT, its anode must be thoroughly discharged. The CRT is a high
vacuum part. Once broken, its fragments will fly out violently. Therefore it must be very
careful in dismantling and loading it.
1.2.2 There are a lot of electronic and mechanical components in PCB that have safety related
features. They are indicated with shadow in the circuit diagram. Please carefully read the
detail list before changing these components.
1.2.3 If the fuse is blown, please change it for the one designated in the list of components.
1.2.4 When changing resistors of 1w or bigger than 1w in PCB, make sure to separate them from
the PCB by10 mm.
1.2.5 Make sure that the wire stays far away from the high voltage or high temperature
components.
Check for the AC leakage current of the metal components exposed out of the cover such as
1.2.6
antenna terminal, screw, metal surface and control axis. Make sure that the cabinet of TV set
is absolutely safe in operation, free from any risk in electric shock. Insert the power supply
plug directly into the 220v AV socket (No isolate transformer will be applied during the test).
Use an AC voltage meter with sensitivity of 5 kΩ or higher per volt to measure the leakage
current according to the following steps:
First, connect in parallel a resistor of1.5 kΩ,10 W resistor and a 0.15 μF capacitor (AC type)
2
A
r
between the known good earthing connector (such as underground metal tube) and the
exposed metal parts out of the cabinet. Measure AC voltage across both terminals. Then
exchange the two pins of AC before re-measuring every exposed metal parts. The measured
value of voltage should not exceed 0.3V effective value, which corresponds to current.0.2mA
If the value exceeds this specified value, aligning must be made at once.
C Volt Mete
Good Earth Connect Point
(Such as underground metal etc)
Figure 1
1.2. 7 DC voltage breakdown test
The following touchable parts must be subject to 1s anti voltage test before packing. The
voltage is applied between the plug pin of the power supply and the exposed metal parts for
the test and the volt value should be AC 3000V.
Parts designation: Position:
Antenna terminal Back cover
This detector is placed
respectively at every
exposed metal parts.
External cover screw Back cover
AV interface Back cover, sides
1.3 Points of attention for product safety
There are many electric and mechanical parts in this PCB that are related to safety. However,
they are often neglected from visual look. For changing the high voltage and high power parts,
very often it’s impossible to provide them with effective “X-ray radiation” protection. All these
exchange parts with safety characteristic are designated in the detail list. All the electronic
parts with such characteristics are indicated with shadow in the circuit diagram.
When changing these parts, please carefully check the detail list.
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t
2 Flow chart of Adjustment and aligning
IF Test
Com
EEPROM
casse
B+volt and 5V-3V
check
Field amplitude,
field linearity
Line amplitude
and east-wes
RF AGC setup
Sound check
Focus course
VG2 adjustment
White balance and
Line field, center and
field amplitude, reset
Set R378 to optimize
Field center
Line amplitude and
Focus fine adjustment
check
High volt
Filament volt
X-ray
Picture &
White
Dark balance
Color
SCART JACK
Brightness
Earphone
jack
Set Av terminal
Sound power
Check of key
Check on
Assembly
Safety check
See Fig.2
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3. Alignment Equipment
3.1 DC Current Stabilizer Power Supply PAB18-1.8
3.2 Audio Frequency Voltage Meter
3.3 Oscillograph
3.4 High Voltage Meter
3.5 Digital Multi-meter
3.6 AC breakdown test meter
3.7 IFT Signal Gene
4. Alignment Instruction
4.1 Factory Alignment Methods
4.1.1 Push composed keys → --/--- → to enter factory menu.
4.1.2 There are totally three pages of factory menu. Turn the page by pushing “MENU”, Move the
items by CH+/CH- key, Adjust the value by VOL+/VOL-. After adjustment, push “OK” for save.
4.1.3 The method to quit factory menu: Under the item VCT in SERVICE XOCECO-50 Hz, push
EXIT: OK
4.2 IF amplifier alignment
a) Connect the positive pole of TP5. C219 to DC 5v, TP2 or TP7 to positive pole DC 8v, TP6 to
earth, TP4 to multi-meter.
b) Connect 38.9M, PAL DK IF signal to TP1 through 1000p capacitor, adjust IFT L102 with zero
inductance screwdriver, to make the readout of multi-meter as 2.5V±0.1 V.
c) Connect 33.9M SECAM L IF signal to TP1 through 1000P capacitor, apply voltage 5v at TP1,
TP3, TP8, adjust RP101 with zero inductance screwdriver, to make the readout of
multi-meter as 2.5V±0.1 V.
d) After adjustment, connect the IF line disconnect point of tuner, seal L102 with wax, point glue
RP 101.
4.3 B+ confirmation
Determine the B+ voltage by DC meter, DC 200V ( C503 two poles) , the value should be 135
V±0.5.
4.4 AGC adjustment
4.4.1 Receive D-8 signal 60db, determine the voltage of positive testing pole of C114 with DC
voltage meter.
4.4.2 Adjust potentiometer RP107, to make the voltage readout of voltage meter to be 4.1 V±
0.1V.
4.4.3 Input 100db from antenna, and the picture should not appear as asynchronized and
distorted. Input 35db-40db weak signal, and the color should not disappear, the picture
should be synchronized, and the sound is normal.
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4.5 Sound inspection
4.5.1 Receive 1kHz sound signal 100% modulated and connect X701 with 8Ω false resistances
(load). Connect sound voltage meter and Oscillograph to two poles of the false resistances.
4.5.2 Turn the sound to the biggest volume. Balance the sound and set the high/low sound to the
middle, MSS OFF, DBE OFF, and the sound power should be ≥7 W×2（about 7.5 Vrms）,
distortion≤7% (A slight peak cutting at maximum sound sine wave is allowed.）
4.6 Alignment of focus potentiometer
4.6.1 Pre-warm the TV set for 30 minutes.
4.6.2 Receive the signal from testing card.
4.6.3 Push the key of picture mode to place analog in “dynamic”.
4.6.4 Adjust potentiometer of FOCUS on the FBT to make the picture to be best focused.
4.7 Alignment of line center
4.7.1 Receive 50 HZ signal from video head.
4.7.2 Enter the factory menu RGB HOR. POSITION item under AV status, adjust amplitude of RGB,
and make the picture to be symmetry. Then save.
4.7.3 Receive 60Hz video signal and enter the factory menu RGB HOR.POSITION item under AV
status. The adjusting method of POSITION is same as 4.7.1～4.7.2.
4.7.4 Adjust separately under following four modes
a）50 Hz 4: 3;
b）60 Hz 4: 3;
Of which Vert position is unnecessary for readjustment after setup at the initial value. Adjust
the value of R378 to optimize it (set it up during the production in the factory).
4.8 Field amplitude, field S alignment, field center, line amplitude, E/W alignment etc.
Enter the corresponding item of factory menu and adjust the geometric distortion until accepted.
Hor Amplitude
Cushion
Trapeze
Angle
Bow
Hor Symmetry
Hor Corners
Vert position
Vert Amplitude
Vert S-Correction
Vert S-Symmetry
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The adjustment result should satisfy the scan linear geometric distortion and over scan (rate of
recurrence)
4.9 Adjustment of screen-grid Focus and VG2
4.9.1 Adjust FBT Focus pole potentiometer until picture is clear.
4.9.2 Enter factory menu Cathode current (G2) item, (AV should be kept empty then), push VOL+,
change to bright horizontal line and adjust the potentiometer of the line pack acceleration pole
in such a way that the bight horizontal line becomes slightly bright.
4.10 White Balance Adjustment
4.10.1 Enter “Cutoff ref” adjustment of factory menu. It’s enough only to fine adjust the dark
balance. Under 4.5 Niete, color temperature 12000K+8MPCD（X=0.270，Y=0.283）.
4.10.2 Enter Drive ref item adjustment of factory menu. The bright balance will be automatically
adjusted at a certain white coordinate place. Under 60 Niete, color temperature
2000K+8MPCD（X=0.270，Y=0.283）.
4.11 Inspection of the high voltage and filament voltage
4. 11. 1 Connect high voltmeter between the high voltage cap and the earth. Measure the filament
voltage with an actual value and effective voltage meter.
4.11.2 Receive D35 signal, set the picture mode at “dynamic”, and measure the high voltage and
filament voltage. The voltage for 29” “Yongxin” extra pure flat should be: high voltage- 29 kV
±0.5 kV; 29″pure flat, high voltage- 30 kV±0.5 kV，filament voltage- 6.3±0.3 Vrms.
4.12 Inspection of X-ray protection
4.12.1 Receive normal picture.
4.12.2 Push switch S301. The line scan should stop vibrating and shut the set off.
4.12.3 Shut off the main power supply, re-power it on in 30 seconds. It should be back to normal.
4.13 Inspection of beam current
Receive D35 signal, set the picture mode at “dynamic”, and measure the two terminals of TP9,
TP10. For ultra pure flat it should be ≤1.6 V, and for 29″pure flat, ≤1.7 V.
4.14 Inspect ion of AV function
VIDEO IN: 1 Vp-p 75Ω, AUDIO IN: -8 dBm±3 dBm ＞47 kΩ.
As per instruction manual, connect audio and video equipment with AV terminal of the set to
be tested. The inter-connection should be made to meet the following requirements:
VIDEO IN: 1 Vp-p 75Ω, AUDIO I: -8 dBm±3 dBm ＞47 kΩ.
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