HT-3718 Service Manual COLOUR TELEVISION Precautions ................................. 1 I. Specifications .............................. 5 2. Alignment and Adjustments ......... 7 3. Schematic Diagrams ................... 56 8. Bolck Diagram............................. 55 7. Electrical Parts List ..................... 41 6. Exploded Views and Parts List .... 40 5. Troubleshooting ........................... 34 4. Features 2 I C bus control Turning TV on/off with curtain-fashion 218 programmes stored Entire channel CATV(470MHZ) Multi-picture and multi-volume modes selection Audio/Video input and output,S-Video terminal Black background protection without signal On-time,off-time,appointing programme English OSD Childlock Haier group
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COLOUR TELEVISION Service Manual · Due to the high vacuum and large surface area of the picture tube, extreme care should be taken in handling the Picture Tube. Do not lift the Picture
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HT-3718
Service ManualCOLOUR TELEVISION
Precautions.................................1I.
Specifications..............................52.
Alignment and Adjustments.........73.
Schematic Diagrams...................56 8.
Bolck Diagram.............................557.
Electrical Parts List.....................416.
Exploded Views and Parts List....405.
Troubleshooting...........................344.
Features2
I C bus controlTurning TV on/off with curtain-fashion218 programmes storedEntire channel CATV(470MHZ)Multi-picture and multi-volume modes selectionAudio/Video input and output,S-Video terminalBlack background protection without signalOn-time,off-time,appointing programmeEnglish OSDChildlock
Haier group
1.PRECAUTIONS INPORTANT SAFETY NOTICE These parts are identified by many electrical and mechanical parts in this chassis have special safety-related characteristics. !in the Schematic Diagram and Replacement Parts List.
It is essential that these special safety parts should be replaced with the same components as recommterminaled in this manual to prevent X-RADIATION, Shock, Fire, or other Hazards.
Do not modify the original design without permission of the manufacturer.
General Guidance
An Isolation Transformer should always be used during the servicing of a receiver whose chassis is not isolated from the AC power line. Use a transformer of adequate power rating as this protects the technician from accidents that might result in personal injury caused by electrical shocks.
It will also protect the receiver and it’s components from being damaged by accidental shorts of the circuitry that might be inadvertently introduced during the service operation.
If any fuse (or Fusible Resistor) in this TV receiver is blown, replace it with a specified one.
When replacing a high wattage resistor (Oxide Metal Film Resistor, over 1W), keep the resistor 10mm away from PCB.
Keep wires away from high voltage or high temperature parts.
Due to the high vacuum and large surface area of the picture tube, extreme care should be taken in handling the Picture Tube. Do not lift the Picture Tube by its Neck.
X-RAY Radiation
Warning:
The source of X-RAY RADIATION in this TV receiver is the High Voltage Section and the Picture Tube.
For continued X-RAY RADIATION protection, the replacement tube must be of the same type as specified in the Replacement Parts List.
Before returning the receiver to the customer,
always perform an AC leakage current check on the exposed metallic parts of the cabinet, such as antennas, terminals, etc., to make sure that the set is safe to operate without any danger of electrical shock.
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SERVICEING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service manual and its supplements and addterminala, read and follow the SAFETY PRECAUTIONS.
NOTE: If unforeseen circumstances create conflict between the following servicing precautions and any of the safety precautions, always follow the safety precautions. Remember: Safety First.
General Servicing Precautions
1. Always unplug the receiver AC power cord from the AC power source before:
a. Removing or reinstalling any component, circuit board module or any other assembly of the receiver.
b. Disconnecting or reconnecting any receiver electrical plug or other electrical connection.
c. Connecting a test substitute in parallel with an electrolytic capacitor in the receiver.
CAUTION: A wrong substitution part or incorrect installation polarity of electrolytic capacitors may result in an explosion hazard.
d. Discharging the picture tube anode.
2. Test high voltage only by measuring it with an appropriate high voltage meter or other voltage-measuring device (DVM, FETVOM, etc.) equipped with a suitable high voltage probe. Do not test high voltage by “drawing an arc”.
3. Discharge the picture tube anode only by (a) first connecting one terminal of an insulated clip lead to the degaussing or kine aquadag grounding system shield at the point where the picture tube socket ground lead is connected, and then (b) touch the other terminal of the insulated clip lead to the picture tube anode button, using an insulating handle to avoid personal contact with high voltage.
4. Do not spray chemicals on or near this receiver or any of its assemblies.
5. Unless specified otherwise in this service manual, clean electrical contacts only by applying the following mixture to the contacts with a pipe cleaner, cotton-tipped stick or comparable nonabrasive applicator; 10% (by volume) Acetone and 90% (by volume) isopropyl alcohol (90%-99% strength)
CAUTION: This is a flammable mixture.
Unless specified otherwise in this service manual, lubrication of contacts is not required.
6. Do not defeat any plug / socket B+ voltage interlocks with which receivers covered by this service manual might be equipped.
7. Do not apply AC power to this instrument and/or any of its electrical assemblies unless all solid-state device heat sinks are correctly installed.
8. Always connect the test receiver ground lead to the receiver chassis ground before
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connecting the test receiver positive lead.
Always remove the test receiver ground lead last.
9. Use with this receiver only the test fixtures specified in this service manual.
CAUTION: Do not connect the test fixture ground strap to any heat sink in this receiver.
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components are usually called Electrostatically Sensitive (ES) Devices. Examples of typical ES devices are integrated circuits and some field effect transistors and semiconductor “chip” components. The following techniques should be used to help reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor component or semiconductor- equipped assembly, drain off any electrostatic charge on your body by touching a known ground ground. Alternatively, obtain and wear a commercially available discharging wrist strap device, which should be removed to prevent potential shock prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ES devices, place the assembly on a conductive surface such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ES devices.
4. Use only an anti-static type folder removal device. Some solder removal devices not classified as “anti-static” can generate electrical charges sufficient to damage ES devices.
5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ES devices.
6. Do not remove a replacement ES device from its protective package until immediately before you are ready to install it. (Most replacement ES devices are packaged with leads electrically shorted together by conductive foam, aluminum foil or comparable conductive material).
7. Immediately before removing the protective material from the leads of a replacement ES device, touch the protective material to the chassis or circuit assembly into which the device will be installed.
CAUTION: Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged replacement ES devices. (Otherwise even some normally harmless motions such as mutual brushing of your clothes’ fabric or lifting of your foot from a carpeted floor might generate static electricity sufficient to damage an ES device.)
General Soldering Guidelines
1. Use a grounded-tip, low-wattage soldering iron and appropriate tip size and shape that will
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maintain tip temperature within the range of 500 oF to 600 oF.
2. Use an appropriate gauge of RMA resin-core solder composed of 60 parts tin/40 parts lead.
3. Keep the soldering iron tip clean and well tinned.
4. Thoroughly clean the surfaces to be soldered. Use a mall wire bristle (0.5 inch, or 1.25cm) brush with a metal handle. Do not use freon-propelled spay-on cleaners.
5. Use the following unsoldering technique
a. Allow the soldering iron tip to reach normal temperature.(500 o F to 600o F)
b. Heating the component lead until the solder melts.
c. Quickly draw the melted solder with an anti-static, suction-type solder removal device with solder braid.
CAUTION: Work quickly to avoid overheating the circuit board printed foil.
6. Use the following unsoldering technique
a. Allow the soldering iron tip to reach normal temperature.(500 o F to 600o F )
b. First, hold the soldering iron tip and solder the strand against the component lead until the solder melts.
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2. TECHNICAL SPECIFICATION 1. PWER SUPPLY AC 90v-250v 50/60Hz
2. COLOUT SYSTEM: PAL SECAM NTSC4.43/3.58 (AV)
3. TV SYSTEM: B/G D/K
4. CRT: 14”
5. AERIAL INPUT IMPEDANCE: 75Ω Standard Coaxial Cable
6. SOUND OUTPUT POWER: ≥1W
7. POWER CONSUMPTION: ≤60W
8. NET WEIGHT (kg): 11
9. NET SIZE (mm): 440 x 355 x 335
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Products functions TYPE
FUNCTIONS
HT-3718
TYPE
FUNCTIONS
HT-3718
IC TA1238 Audio output power(w) 1W
Tube 14 Super woofer
Color system PAL SECAMNTSC3.58/4.43(A V) NO of built-in speakers 2
Broadcast system B/G D/K Analog surround stereo
No.of preset channels 218 Treble/bass lifting and balancing
CATV band width 470MHZ Multiple audio mode
Blue/black screen black AV stereo
Menu OSD Digital reverberation
OSD language English Tone control
Manifold PIC modes Auto volume leveling
Program preview MuteY/C separation circuit 3D surround soundDenoise circuit SRSBlack level extend MAX volume presetBlue level extend 5 bands equalizerAuto skin color correction
AUDIO
NICAM adjustment AV in Rear 1
Dynamic high voltage stabilizing AV out Rear 1Dynamic focusing S terminalDouble focusing DVD signal inputDynamic white peak clipping KARAOK terminal
Color resolution lift Stereo headphone socket
4 2 2 PIC window positioning VGA
Pull-curtain type on /off display NO. of Australian standard sockets
Artificial intelligence Service terminalSVM HI-FI audio signal output terminalCTI External super bass terminalLTI
TERMINALS
DC current output
Video signal digitalization Timer off(MINS) 120
Teletext Timer on
Still frame Auto off upon no signal
Multi PIC Frames AC off
PIP independent tuner Stand by
PIP double tuner Frequency synthesis tuning
PIC out PIC Tension synthesis tuning
9 programs preview Automatic color system identify
100Hz I2C bus-masteringZOOM AV in AV out
Stepless zoom in/out Wireless earphone(infrared)
16 9 mode Handset position notify(beep)
Logo configure Automatic channel preset
Skip Partial automatic channel preset
Supper receiver
CONTROL
Manual channel preset
Calendar Total power input(W) 60W
Memo book/games Voltage range(V) AC150V-250V
Favorite channels Power frequency(Hz) 50HZ
Child lock Packaged weight(Kg) 12Kg
SPECIFICATIONS
Packaged dimensions(mm) 500*415*390Type of power plug
IMAGE
OTHERV-CHIP CCD
Attention: already have * you can choose it or not
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3.Alignment and Adjustments Functions: • I 2C bus control
• Display Full Function on Screen and infrared Remote Control
• ASM System and fine Circuit, 100 Programs stored from 0 to 99
14 Analog R signal input 1.1 1.1 800 3000 15 Analog G signal input 1.1 1.1 800 3000 16 Analog B signal input 1.1 1.1 800 3000 17 RGB(image and message
circuit) power supply 9.0 9.0 450 600
18 R signal output 1.8 2.8 760 1500 19 G signal output 1.8 1.8 760 1500 20 B signal output 3.0 3.0 720 1400 21 ABCL control pin 5.3 5.3 820 2000 22 Field sawtooth wave forming 4.2 4.2 750 2000 23 Field feedback signal 5.0 5.0 820 2000 24 Field driving signal output 0.9 0.9 720 900 25 Field AGC 0.2 0.2 800 2000 26 Bus clock signal 3.0 3.0 720 15000 27 Bus data signal 3.0 3.0 720 15000 28 Deflection circuit power
supply 9.0 9.0 450 600
29 PAL/NTSC identification signal output SECAM identification signal input
25 Character blanking 0 0 620 2200 26 Line flyback 4.0 4.0 680 10000 27 Field flyback 4.8 4.8 680 10000 28 Character oscillating 5.0 5.0 600 10000 29 Character oscillating 3.0 0 10000 30 Grounding 0 0 0 31 CPU clock 0.4 700 10000 32 CPU clock 2.0 700 10000 33 CPU reset 0 650 40000
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Reference Voltage(V) Reference Resistance Pin Function Without With Forward(Ω) Backward(Ω)signal signal
34 Vacant pin 4.8 700 10000 35 Infrared receiving input 3.8 700 10000 36 Line synchronizing signal
input 4.2 700 10000
37 Clock bus control 0.8 700 10000 38 Data bus control 3.0 700 10000 39 Vacant pin 4.2 700 10000 40 Vacant pin 4.2 700 10000 41 Vacant pin 0 700 10000 42 Power supply 5.0 420 2700
N101 LA7910 Reference Voltage(V)
Reference Resistance Pin Function
Without signal Forward(KΩ) Backward(KΩ)1 Output (BU) 0 120 7.2 2 Output (BH) 12.5 17.5 7.5 3 Control input 12.5 6.5 8.5 4 Control input 0 6.5 9.0 5 Grounding terminal 0 0 0 6 Power input terminal 1 14.0 6.0 50 7 Output (BL) 0 1.5 1.5 8 Vacant pin 0 8.5 9 Power input terminal 2 9 0.5 0.5
3. Signal processing
(1) Picture intermediate signal processing
Having been under tuning and selective calling, high frequency amplification and frequency mixing in tuner A101, the high frequency signals are output through the intermediate frequency signal output terminal (IF) of A101 to the base electrode of intermediate frequency pre-amplifier V101 via the coupling matching network. The intermediate signals are added to Pin 6 and 7 of the symmetric terminals of the intermediate difference channel of the TV signal monolithic processing circuit N201 (TB1238N). The intermediate signals are amplified in N201 and the PLL picture modulated. The mixed signals of picture video and the second sound are output from Pin 47 and then divided into two.
(2) Picture signal processing
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The signals from Pin N201 (47) go through the sound intermediate frequency wave trap Z235 (D/K system) or Z236 (B/G system) and the emitter follower V212 so that the video complete TV signals are got out and sent to TV/AV electronic switch circuit through Pin (43). One part of the output signals go into the video signal processing circuit, the other go in the color signal processing circuit via C/VIDEO electronic switch.
The video signals into the video signal processing circuit are amplified by 6dB gain. Then one part of the signals are sent to the scanning unit and horizontal and vertical signals are output through Pin (32) and (24) after horizontal and vertical oscillation.
The other part of the signals is output via Pin (35) to Pin (39) after being followed and resistance voltage divided for 6dB attenuation by V251. The video signals are input into carrier wave trap circuit and the color signals are removed. Then they enter the Y/VIDEO switchover circuit to be sent to the video unit.
C/VIDEO electronic switch outputs video complete TV signals or the color signals to the band-pass/high-pass filter circuit. The color signals are got out and sent to the chrominance unit. The R-Y, B-Y and G-Y signals output from chrominance unit are sent to the matrix unit together with Y signal output from the video unit to generate R, G and B primary color signals, which are then output via Pin (18) (19) and (20) into the final circuit CRT board to the picture tube circuit.
Tuning reverse code PWM signals are output from super central microprocessor D901 via Pin (2). With reverse phase amplification and integrator processing by V975, PWM signals become D.C. tuning voltage and are added to the tuning voltage input terminal (TU) of the tuner A101. The control signals are output from Pin (9) (10) of D901 into N101 wave band switchover. The wave band switchover is as follows:
N101 La7910 Band Switch Truth Table
Input Output Working band 3 4 1 2 7 8
VL L L L L H L
VH H L L H L L
U L L H L L L
CATV H H L L L H
(3) External audio and video signal processing
The video input signals are sent into the TV/AV electronic switch via N201 Pin (41) through XS212 VIDEO IN after being coupled by C252.
The audio input signals are sent into TV/AV electronic switch via N201 Pin (55) through XS212 AUDIO IN after being coupled by C207. The picture and sound signal processing is carried out by N201 (TB1238N).
(4) Sound signal processing
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The combined signals of picture video and the second sound intermediate frequency are output from Pin (47) and sent into the sound intermediate frequency circuit SIF unit to be processed via N201 Pin (53) after being filtered and switched over by sound intermediate frequency band-pass filter Z233 or Z234. The sound audio signals obtained are then sent into the audio switch circuit of the TV/AV electronic switch circuit. After the electronic volume attenuation by ATT circuit, they are output to the sound amplification circuit N701 via the input terminal Pin (6). The sound power amplification is carried out by LA4275. Finally, the signals are output to loudspeaker SP901 and SP902.
(5) Horizontal scanning signal processing
Switch on the set and 9V voltage is sent to N201. The horizontal start voltage is provided by the internal regulated voltage circuit to make VCO generate 32-fold horizontal frequency oscillation. With 1/32 frequency distributor and AFC1 and AFC2 phase-shifting circuit, the horizontal drive pulse generated is output via Pin (32) to drive horizontal driver V444 to make it work in switch status. The switch pulse is coupled by the horizontal drive transformer T401 and make the horizontal output tube V411 work in switch status. The output signals are sent to the horizontal deflection coil via S correction capacitance C412 and horizontal linearity adjustment L414. One linearly varying magnetic field is generated to make the electron beam of the picture tube move horizontally until the horizontal scanning completes.
About 22KV anode high voltage, 8KV focusing voltage and 6.3 Vrms filament voltage is generated via horizontal output transformer T402 by making use of the pulse high voltage generated on the collector electrode of the horizontal output tube V411 during the horizontal scanning return period. Apart from this, one part of the return pulse voltage output from Pin 5 of T402 is sent to Pin 26 of CPU after phase reverse to be used as synchronizing signal; and the other part is sent to Pin 30 of N201 via phase shifting network to implement AFC 2 control.
(6) Vertical scanning signal processing
The vertical oscillation signals output from Pin 24 of TB1238N are added to the vertical scanning saw tooth wave signal output terminal Pin 4 of vertical scanning module LA7830 via R908. Vertical scanning saw tooth wave signals are formed with the differentiation by driving the internal differential amplifier. Finally, saw tooth wave signals are output from Pin 2 and added to deflection coil. Vertical deflection of the electron beam is generated to implement the vertical scanning.
(7) Power supply circuit
The power supply circuit of HT-3718 is a typical free-running pulse width switch power supply. The structure of the main circuit belongs to step-down type. It is a cold mechanism power supply. The circuit is mainly composed of switch tube V513, exciter tube V512, switch transformer T501 and rectifying filter circuit. The AC220V power voltage is rectified by diode D503 to D506 and smooth filtered by C507 and voltage about DC 300V is got. The voltage is added to the collector electrode of switch tube V513. V513 and the primary group 3-7 and the feedback winding 1-2 of the switch transformer T501 form a free-running blocking oscillator. About 560VP-P intermittent oscillation pulse is generated at the collector
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electrode of V513, the pulse width of which is controlled by capacitance C514. The collector electrode and emitter of V512 are merged between the base electrode and the emitter of switch tube V513. The conducting state of V512, i.e., the current through V512 controls the conducting time of V513. If the current through V512 is high, the conducting time of V513 is short and the voltage low. If the current through V512 decreases, i.e., the shunting effect decreases, the conducting time of V513 is long and the voltage high. The working status of V512 is controlled by the control circuit composed of V551, VD551 and VD515. Direct sampling is adopted for the control circuit and the photocoupler transmits error information. V551 is error comparison amplifier. VD515 transmits error information. The error information changes the current through V511 and the change generates error voltage on resistance R515 to control the conducting state of V512, thus the conducting time of V513 is changed and the purpose of width is achieved. When the output DC voltage B1-115V increases, the current through V551 increases by the photocoupler, so the current through V512 increases, making the conducting time of V513 shorter, output voltage lower, thus achieving the purpose of regulation, and vice versa. With VD554 rectification, C559 filtering and V552 control, the pulse voltage supplied by the secondary pole of the switch transformer becomes 26V, which is supplied to vertical scanning circuit. With VD553 rectification, C557 filtering, 15V voltage is obtained, which is then regulated through three-stage adjustment to become the 12V, 9V and 5V voltage supplying to the main chassis circuit.
DISASSEMBLY INSTRUCTIONS
A. Important note
This set is disconnected from the power supply through the converter transformer. An isolating transformer is necessary to service operations on the primary side of the converter transformer.
Back Cabinet Removal
Remove the screw residing on the back cabinet and carefully separate the back cabinet from the front cabinet.
B. Picture tube handling caution
Due to high vacuum and large surface area of picture tube, great care must be exercised when handling picture tube. Always lift picture tube by grasping it firmly around faceplate.
NEVER LIFT TUVBE BY ITS NECK! The picture tube must not be scratched or subjected to excessive pressure as fracture of glass may result in an implosion of considerable violence which can cause personal injury or property damage.
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Adjustment A. Safety Precautions 1. It is safe to adjust after using insulating transformer between the power supply line and chassis input to prevent the risk of electric shock and protect the instrument.
2. Never disconnect leads while the TV receiver is on.
3. Don't short any portion of circuits while power is on.
4. The adjustment must be done by the correct appliances. But this is changeable in view of productivity.
5. Unless otherwise noted, set the line voltage to 220Vac±20%, 50/60Hz.
B. Adjusting items
1. Equipment, instruments and tools:
(1) One process assembling machine for 14" color TV
(2) One 100MHz oscilloscope
(3) One three-digit voltmeter
(4) One AC regulated power supply
(5) Factory standard signal cable input system
(6) One user remote controller
(7) One adjusting tool
2. Adjusting method of main voltage (112V) and intermediate frequency detection (38.9 MHz):
(1) Connect the main baseboard to a 14″ factory-assembled color TV set and connect the company’s adjusting signal.
(2) Switch on 220V AC main power supply and receive the electronic circular signal. Adjust accelerating pole and focusing pole to appropriate position. Press the picture memory mode button (PP) on the user’s remote controller to get into “MEMORY2” status.
(3) Ground the black rod of digit voltmeter and connect the red rod to R553. Adjust the potentiometer RP551 (2K) until the digit voltmeter indicates 115±0.5 V. (4) Use factory special remote controller for adjustment (V.) by pointing it to the baseboard infrared receiver and pressing S-PVOC button. Then the factory-assembled color TV displays AFT (dark field)---AFT OK (with signal or noise), intermediate frequency detection (38.9MHz) adjustment finishes.
3. Baseboard testing method:
(1) Connect the main baseboard to a 14″ factory-assembled color TV set, and connect the company’s adjusting signal.
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(2) Switch on the 220V main power supply and press the P+, P- buttons on user’s remote controller to check grid, electronic circle, color bar, test card (without color), three primary colors, color test card signals on position number 0, 1, 2, 3, 4, 5 respectively. It is required that no program is missed, otherwise use auto search or manual search to have all the signals received.
(3) Receive the color test card signal. When you adjust the control of volume, contrast, brightness, color saturation, clarity, the sound and picture shall change accordingly.
(4) For TV system test, select the system control menu with the remote controller to have the following displayed on the menu screen:
Color AUTO
Sound D/K (or B/G)
(5) To test the AV input, press TV/AV button and the TV-AV picture signals will be displayed in turn. Corresponding audio and video input signals shall be observed on the oscilloscope and the picture and sound of the factory-assembled TV set shall be proper.
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4. Adjustment
(1) Enter the D-MODE maintenance state with special remote controller
Press the D-MODE ON/OFF button on the factory remote controller 1 to enter the maintenance state. Character D will appear on the top right corner of the screen and the following items and data to be adjusted on the top left part:
RCUT 20 D
After entering the adjustment state, press button↑ or ↓ to select the item and button →or ← to adjust the data of that item.
Example:
a. Adjustment of horizontal center, frame center and frame size.
Receive standard test card signal and adjust the brightness, contrast and chrominance to the middle position. Press button D-MODE ON/OFF to enter the maintenance adjustment state. Press button ↓ to select the horizontal center (HPOS) to be adjusted. Press button →or ← until the horizontal center of the picture is in the center of the screen. The horizontal center is properly adjusted.
Next, adjust the frame center of the picture. Press button ↓ to select the frame center (VP50) to be adjusted. Press button →or ← until the frame center of the picture is in the center of the screen. The frame center is properly adjusted.
Finally, adjust the frame size of the picture. Press button ↓ to select the frame size to be adjusted (HIT). Press button →or ← until the frame size is full on the screen.
When the adjustment completes, press button D-MODE ON/OFF to quit the D-MODE maintenance adjustment state. The D on the top right corner of the screen disappears. You can also quit the D-MODE maintenance state with remote control.
b. dark balance adjustment
First, enter D-MODE to check if the preset data of red, green and blue guns are correct. The RCUT item appears first. Adjust button →or ← until the data of RCUT is 20. Press button ↓ to select the GCUT item and make the data of GCUT 20. Press button ↓ to select the GCUT item and make the data of BCUT 20. All the preset data of the dark/bright balance of each gun are adjusted in this way as shown in the following table
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Item Data Content
RCUT 20 Red dark balance
GCUT 20 Green dark balance
BCUT 20 Blue dark balance
GDVR 40 Green bright balance
BDVR 40 Blue bright balance
Press the ⊟ button on the remote controller. A horizontal bright line will appear on the screen. Then adjust the screen grid (G2) potentiometer on the horizontal output transformer in such a way that the bright line on the screen is just visible. If a red horizontal bright line appears, press down button blue + while pressing red + until the line turns purple. If it exceeds, press button blue – until the line turns purple. Then press button green + to turn the line into white. If it exceeds, press button green – until the line turns white. Finally, press button ⊟ to recover the screen.
c. Bright balance adjustment
Adjust the brightness and contrast control to make the screen brighter and the chrominance off. Press the item selection buttons for green or blue bright balance. Adjust the brightness and contrast control to make the screen darker and check the white balance of the low brightness. If the dark balance is not proper, adjust the dark balance adjusting button to achieve good white balance for low and high brightness. The white balance adjustment finishes. Finally, switch off the set with the remote controller and quit the maintenance adjustment state.
Note: many maintenance item adjustments can be done with I2C bus control. They are not explained one by one hereby. The adjustment item states are listed below for the maintenance personnel:
(2) Enter the S-MODE state with the user remote controller
Press the volume down button on the set until the volume is 00 on the screen. Keep holding it and press button DISP on the remote controller. Character S appears on the top right corner of the screen, indicating that it is S-MODE maintenance state. The following is shown on the screen:
RCUT 20 S
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S-MODE includes the most often used items. Press the program up or down button to select the item to be adjusted. Then press volume up or down button to adjust the data. The following is the S-MODE adjustment list for reference for the maintenance personnel:
Item Data Content Item Data Content
RCUT 20 Red dark balance HPOS 0C 50Hz horizontal center
GCUT 20 Green dark balance VP50 01 50Hz frame center
BCUT 20 Blue dark balance HIT 25 50Hz frame size
GDVR 40 Green bright balance VLIN 0C 50Hz frame linearity
BDVR 40 Blue bright balance SBY 01 SECAM B-Y
COLC 40 Chrominance intermediate value
SRY 04 SECAM R-Y
TNTC 40 Tone intermediate value
RAGC 23 High amplification AGC
COLS 40 S system chrominance
intermediate value
SCNT 00 Subcontrast
When the adjustment finishes, do not forget to switch off the set with the remote controller to quit the S-MODE maintenance state.
(3) Parameter record list for factory adjustment items
HT-3718 Factory Adjustment (D-MODE) Items Data Reference List
Item Data Content Item Data Content
RCUT 1A Red dark balance HITS 00 50/60Hz frame size
GCUT 39 Green dark balance VLIN 0B 50Hz frame linearity
BCUT 1E Blue dark balance VSC 06 Frame S correction
HIT 0D 50Hz frame size Automatic recognition system
HPS 03 50/60 Hz horizontal center
OSD 07 Screen display width adjustment
VP60 01 60Hz frame center OPT 06 Optional
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1. No raster and no sound
Check the fuse
Check VD503∼VD506 V513 C507 Check loading voltages of 112V 150V
Check if the connector electrodevoltage of V552 is 26V.
Check if all loading resistors are normal
Check 12V9V 5V
Check V552 orCPU POWERcontrol circuit
Check D902V902 andV901
There is breakdown inhorizontal circuit andN201
Check switchpower circuit
Check if rectifierdiodes breakdown
Replace therectifier diodes
Loading has breakdown
Normal Abnormal
Normal Abnormal
Normal Abnormal Normal Abnormal
Normal Abnormal
Normal Abnormal
4.TROUBLESHOOTING
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There is breakdown in
CRT broad
Check circuit between pin18 pin20 in N201
No raster
Check if G2 voltage on CRT board is normal
Check heater voltage Check the base electrode voltage of V444
2.
Check the voltagebetwecn bace electrodeand connector electrodeof v411
Check the circuitbetween pin 32 atN201 and H drivegrade
Check allvoltages ofpins at X602
The heaterresister isbroken.
Check the connectorelectrode voltage ofV411
There is breakdown inhorizontal drive grade, CheckV444 T401 R437
V411 is rosin jointor broken
Check if FBT T402 V411orC415 C416 are leakage ofelectricity
Check if pin28 voltage 9Vat N201 isnormal
Rechange badcomponents orremedy contentcircuit.
Check the horizontal oscillationexternal circuit of Z280 N201 andN201
Check 9V power circuit
Normal Abnormal
Normal Anormal
Normal Abnormal
Normal Abnormal
Yes
No
Higher Lower
Normal Abnormal
Normal Abnormal
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Horizontal bright line
Break R908 , let multimeter preset on R 1K and red meter rodgrounding, let black meter rod tap pin 4 at N402.see if the bright line canwide at instant.
Check if R907 R448 are rosin joint and the resistor value of R448 changes larger.
Check theexternal circuitof N201 andN201.
Normal
There is breakdown in the verticaloutput grate.
Check if the connectorof the deflection yoke isconnected well,andC433is rosin joint orcutoff, and the externalcircuit of N402 andN402.
Check 26Vpower circuit.
YES NO
YES NO
YES NO
3.
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4.Picture OK, no sound
Break C700,let red meter rod ground and let black meter rod tap pin6 at N701, the speakers has snapping.
If power amplifier is normal ,check N201 sound IF circuitand N201.
Break the connector electrode ofV701, let the black meter rodtap pin 6 at N701 , see if thespeakers have snapping.
There is breakdown in soundmute circuit, check V701,V903
Check if there is 16.5V voltage
Check sound power amplifierN701 and circuit , speaker.
Check 16.5V power circuit.
4.
Yes No
Yes No
Yes No
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RASTER OK, NO PICTURE, NO SOUND
Whether there are noise dots?
Check RAGC item of ICbus is set “00”.
Whether there are voltagesin every pin of tuner
Use the remote controller andenter S-MODE and adjustRAGC to near 2D
Check picture IF channeland V231, V212, N201
Aerial system or tunerbreaks down.
Check the circuitbetween CPU andtuner.
NO YES
YES NO
YES NO
NO red
Check if V622 is rosin joint or break?
Replace V622 or joint. Check the voltage of pin 1 at XS602
Check V621, R621 Check the circuit between pin 18 atN201 and pin 3 at XS261
YES NO
YES NO
5.
6.
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7. No words
There is black words?
Check L902,C926,C925 Check the circuit between pin 22pin 24at D901 and pin 14pin 16 at N201
Replace thecompartment
Normal Abnormal
Check the circuit betweenV922,R915,C450 and pin 5 atFBT.