Changhong Electric 21BM91 Service Manual
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Changhong Electric 21BM91 Service Manual

Changhong Electric 21BM91 Service Manual

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FILE NO. SM-CTV-O-155
COLOR TELEVISION
SERVICE MANUAL
MODELNO.
21BM91
CHASSIS NO. CN-18EA
(V2)
Please read this manual carefully before service.

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Summary of Contents for Changhong Electric 21BM91

  • Page 1 FILE NO. SM-CTV-O-155 COLOR TELEVISION SERVICE MANUAL MODELNO. 21BM91 CHASSIS NO. CN-18EA (V2) Please read this manual carefully before service.

  • Page 2: Table Of Contents

    TABLE OF CONTENTS SPECIFICATIONS ......................1 SAFETY INSTRUCTIONS AND MAINTENANCE ........2 X-RAY RADIATION PRECAUTION..................2 SAFETY PRECAUTION ......................2 PRODUCT SAFETY NOTICE....................3 SAFETY SYMBOL DESCRIPTION ..................4 MAINTENANCE........................4 ADJUSTMENTS ........................ 5 SET-UP ADJUSTMENTS ......................5 CIRCUIT ADJUSTMENTS....................... 8 STRUCTURE AND CHASSIS FUNCTION DESCRIPTION ....

  • Page 3: Specifications

    SERVICE MANUAL SPECIFICATIONS Table 1 Specifications 21BM91 Model Number Color PAL, NTSC3.58, NTSC4.43, SECAM system RF system Sound B/G, D/K, I, M system Video system PAL4.43, NTSC3.58, NTSC4.43, SECAM (50/60Hz) Channels preset 236 (0-235) Antenna input 75 (unbalanced) Picture tube...

  • Page 4: Safety Instructions And Maintenance

    SERVICE MANUAL SAFETY INSTRUCTIONS AND MAINTENANCE “ WARNING: BEFORE SERVICING THIS CHASSIS, READ THE X-RAY RADIATION ” “ ” “ ” PRECAUTION SAFETY PRECAUTION 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.

  • Page 5: Product Safety Notice

    SERVICE MANUAL 4. When replacing ICs, use specific tools or a static-proof electric iron with small power (below 35W). 5. Do not use a magnetized screwdriver when tightening or loosing the deflection yoke assembly to avoid electronic gun magnetized and decrement in convergence of the CRT. 6.

  • Page 6: Safety Symbol Description

    SERVICE MANUAL SAFETY SYMBOL DESCRIPTION The lightning symbol in the triangle tells you that the voltage inside this product may be strong enough to cause an electric shock. Extreme caution should be exercised when working on the TV with the back removed. This is an international hazard symbol, telling you that the components identified by the symbol have special safety-related characteristics.

  • Page 7: Adjustments

    SERVICE MANUAL ADJUSTMENTS SET-UP ADJUSTMENTS The following adjustments should be made when a complete realignment is required or a new picture tube is installed. Perform the adjustments in the following order: 1. Color purity 2. Convergence 3. White balance Notes: ①...
  • Page 8 SERVICE MANUAL Fig. 1 2. Convergence Adjustment Preparation: Before attempting any convergence adjustment, the TV should be operated for at least 15 minutes. 2.1 Center convergence adjustment 2.1.1 Receive dot pattern. 2.1.2 Adjust the brightness/contrast controls to obtain a sharp picture. 2.1.3 Adjust two tabs of the 4-pole magnet to change the angle between them and red and blue vertical lines are superimposed each other on the center of the screen.
  • Page 9 SERVICE MANUAL deflection yoke assembly on the picture tube. 2.2.6 Detach the temporarily mounted wedge and put it in either upper space. Fasten the deflection yoke assembly on the picture tube. 2.2.7 After fastening the three wedges, recheck overall convergence and ensure to get optimal convergence.

  • Page 10: Circuit Adjustments

    SERVICE MANUAL CIRCUIT ADJUSTMENTS Preparation: Circuit adjustments should be made only after completion of set-up adjustments. Circuit adjustments can be performed using the adjustable components inside the TV set. For TVs with C bus control, first change the bus data. 1.
  • Page 11 SERVICE MANUAL 3. High Voltage Inspection Measure voltages of test points on the main PCB with the digital voltmeter. Measure the CRT high voltage with the high-voltage testing equipment and heater voltage with the high-frequency effective voltmeter. The rated values are shown as below. Table 3 Test Point Voltage (V)
  • Page 12 SERVICE MANUAL with a DC-500 high resistance meter and insulation resistance between the naked metal and degaussing coil to be over 20MΩ. 6. SERVICE mode 6.1 To enter the DESIGN/SERVICE mode Set the volume to 0. Then press and hold the MUTE button on the remote control, and press the MENU button on the TV to enter the SERVICE mode.
  • Page 13 SERVICE MANUAL 0: No 1: Yes Bit7 Write-in LOGO Refresh AV terminals in main 0: Yes (Recommended) 1: No Bit6 cycle Bit5 RF NTSC options 0: No 1: Yes Bit4 Screen saver 0: No 1: Yes MODE1 Bit3 0: No 1: Yes Bit2 0: No...
  • Page 14 SERVICE MANUAL Waiting time when changing 1: Fast (1 sec.) 0: Slow (2 sec.) BIT 6 channels with 0-9 buttons (Recommended) 1: No 0: Yes BIT 5 DVD option (Recommended) 1: Large step (Recommended) 0：Small Step length setting for lighting up BIT.4 gradually during power-on step...
  • Page 15 SERVICE MANUAL Bit 5 No use Large-amplitude AFT switch when no Bit 4 1: Off 0: On signal 0：927mVrms at 25kHz/dev Bit 3 Audio gain switch in MONO mode 1：500mVrms at 25kHz/dev Bit 2 Y-MUTE when changing channels 0: No 1: Yes Turn-on logo...
  • Page 16 SERVICE MANUAL Adjusting difference between horizontal centers in PAL and NTSC VP60 V phase (60Hz) 0: V phase delay, 0H 7: 7H Adjusting difference between vertical amplitudes in PAL and NTSC HITS VLIN V-linearity 0: -15% 8: 0% F: 15% V-S correction 0: -16% 8: 0%...
  • Page 17 SERVICE MANUAL Table 5 Bus Data Item Data Item Data Item Data Item Data *MODE0 SCNT HPOS BSNS *MODE1 CNTC VP50 *MODE2 CNTN STBY *MODE3 BRTX *MODE4 BRTN VP60 VBLK *LANG COLX HITS UCOM NOT MENU COLN VLIN VTST MEUN ICON TNTX PYNX MAIN MEUN...

  • Page 18: Structure And Chassis Function Description

    SERVICE MANUAL STRUCTURE AND CHASSIS FUNCTION DESCRIPTION 1. STRUCTURE BLOCK DIAGRAM 9V-2 Power Circuit 220V 120V 50Hz STR-G5653 N801 5V-1 5V-2...

  • Page 19: Block Diagram For Supply Voltage System

    SERVICE MANUAL 2. BLOCK DIAGRAM FOR SUPPLY VOLTAGE SYSTEM...

  • Page 20: Chassis Description

    3. CHASSIS DESCRIPTION General Description CN-18EA(V2) chassis is applied in 21BM91 series. By use of Toshiba V/C/D-MCU 2IN1 IC for TV small signal processing and bus control, the chassis enables TV tuning, adjustment, control and picture correction, featuring high-integration, high-performance-to-price ratio and high- reliability and compact circuit with fewer external components.

  • Page 21: Service Data

    SERVICE MANUAL SERVICE DATA TECHNICAL DATA OF KEY ICS 1. TOSHIBA 2IN1 IC SERIES 1) General Description Toshiba 2IN1 IC series are super ICs combined small signal processing with 8-bit micro control unit, including TMPA8801/8802/8803/8807/8808/8809/8812/8813/8821/8823/ 8827/8829 with the following features. Table 7 Type Packag...
  • Page 22 SERVICE MANUAL TMPA8801/8807CMBNG /CPBNG/CRBNG /CSBNG MCU AND SIGNAL PROCESSOR FOR A PAL/NTSC/SECAM TV The TMPA8801/8807CMBNG /CPBNG /CRBNG /CSBNG is an integrated circuit for a PAL/NTSC/SECAM TV. A MCU and a TV signal processor are integrated in a 64-pin shrink DIP package. The MCU contains 8-bit CPU, ROM, RAM, I/O ports, timer/counters, A/D converters, an on-screen display controller, remote control interfaces, IIC bus interfaces and the Closed...
  • Page 23 SERVICE MANUAL 2). Features * High speed 8-bit CPU (TLCS-870/X series) CCD Decoder * Instruction execution time: 0.5 μs(at 8 MHz) * Digital data slicer for NTSC * MPA8801/8807CMBNG) 32-Kbytes ROM, 2-Kbytes RAM * Clock generation for OSD display (TMPA8801/8807CPBNG) * Font ROM characters: 384 characters 48-Kbytes ROM, 2-Kbytes RAM * Characters display: 32 columns×12 lines...
  • Page 24 SERVICE MANUAL 3). Block Diagram for TMPA8801 Fig. 8...
  • Page 25 SERVICE MANUAL 4). Block Diagram for TMPA8807 Fig. 9...
  • Page 26 SERVICE MANUAL 5). Basic Structure 5.1). Internal Connections TMPA8801/8807 has two pieces of IC chip in one package, using Multi-Chip-Package (MCP) technology. One is a micro controller (MCU) and the other one is a signal processor (SP) for a color TV. There are some internal connections between these two ICs for handling below signals.
  • Page 27 SERVICE MANUAL of functions work properly, so that designing the oscillation frequency accurately is required. The spec crystal is recommended to be within fosc: 8 MHz +/-20 ppm ftemp: 8 MHz +/-40 ppm (-20°C to +65°C) While RESET of MCU is active, the MCU function stops. Hardware and software initialization sequence including power supplies control is required, because status of any hardware after the RESET period is unknown especially horizontal oscillator which is a very basic timing generator of SP operation.
  • Page 28 SERVICE MANUAL uP AVDD Power VDD for OSD Oscillator circuit Supply Supply 5 V P52/SDA (SDA) (I/O) IIC bus serial data input/output P51/SCL (SCL) (I/O) IIC bus serial clock input/output P50/PWM 7 bit/TC2/ Int0 7-bit D/A conversion (PWM) output (/PWM8) (output) Timer/Counter input (TC2)
  • Page 29 SERVICE MANUAL Terminal to be connected capacitor to generate V saw signal. V saw V saw amplitude is kept constant by V AGC function. V OUT Output terminal for Vertical driving pulse. H.VCC 9 V VCC terminal for DEF circuit. Supply 9 V. -(For TMPA8801) Connect to GND via resister Terminal for switching of PIP mode...
  • Page 30 SERVICE MANUAL IF VCC 5 V VCC terminal for IF circuit. Supply 5 V. S-Reg.F Terminal to be connected capacitor for stabilizing internal bias. Deemph/ Terminal to be connected capacitor for SIF Det Audio out De-Emphasis. IF AGC Terminal to be connected with IF AGC filter.
  • Page 31 SERVICE MANUAL 7). Microcontrollers Descriptions (MROM version: TMPA8801/8807CMBNG /CPBNG /CRBNG /CSBNG) Fig. 10 8) Refer to Table 18 and Table 19 about Data of the IC’s Pins.
  • Page 32 SERVICE MANUAL 2. AUDIO POWER AMPLIFIER TDA8943SF 6 W MONO BRIDGE TIED LOAD (BTL) AUDIO AMPLIFIER 1). General description The TDA8943SF is a single-channel audio power amplifier with an output power of 6 W at an 8 Ω load and a 12 V supply. The circuit contains a Bridge Tied Load (BTL) amplifier with an all-NPN output stage and standby/mute logic.
  • Page 33 SERVICE MANUAL 4.1) Pinning Fig 12. Pin configuration. 4.2) Pin description Table 11 Pin description Description Symbol OUT− negative loudspeaker terminal supply voltage OUT+ positive loudspeaker terminal positive input IN− negative input half supply voltage decoupling (ripple rejection) MODE mode selection input (standby, mute, operating) ground n.c.
  • Page 34 SERVICE MANUAL 3. TDA8944J 2 X 7 W STEREO BRIDGE TIED LOAD (BTL) AUDIO AMPLIFIER 1). General descriptio n The TDA8944J is a dual-channel audio power amplifier with an output power of 2 × 7 W at an 8 Ω load and a 12 V supply. The circuit contains two Bridge Tied Load (BTL) amplifiers with an all-NPN output stage and standby/mute logic.
  • Page 35 SERVICE MANUAL 4). Pinning information 4.1) Pinning Fig 14. Pin configuration. 4.2) Pin description Table 12 Pin description Symbol Description OUT1− negative loudspeaker terminal 1 GND1 ground channel 1 supply voltage channel 1 OUT1+ positive loudspeaker terminal 1 n.c. not connected IN1+ positive input 1 n.c.
  • Page 36 SERVICE MANUAL half supply voltage decoupling (ripple rejection) IN2+ positive input 2 n.c. not connected OUT2− negative loudspeaker terminal 2 GND2 ground channel 2 supply voltage channel 2 OUT2+ positive loudspeaker terminal 2 TDA8944J: Stereo power amplifier, Max output power: 2×7W 5) Refer to Table 20 about Functions and Data of the IC’s Pins.
  • Page 37 SERVICE MANUAL 4. TV Sound Processor TA1343N TA1343N is a sound processor controlled by I C bus. It incorporates the following: 2-channel input, 3-channel output signal processing circuit, phase shift circuit for surround, and LPF for woofer channel. ALS (Automatic Level Suppresser) circuit which prevents distort the signal in large signal condition for woofer channel is also incorporated 1) Features •...
  • Page 38 SERVICE MANUAL 3) Terminal Function Table 13 Pin No. Name Function DC offset canceling filter for bass boost. Offset canceling filter Connect a capacitor (10[µF]) between this terminal and GND. Terminals for capacitors of the phase shift blocks. φ5 φ4 Value of phase shift each block is φ[deg.]=-2tan (2πfCR).
  • Page 39 SERVICE MANUAL Vcc terminal. Recommended operation voltage is 9[V]±10[%]. Smoothing filter for volume control. Volume filter Connect a capacitor (0.01[µF]) between this terminal and GND. Smoothing filter for bass boost level control. Woofer LPF Connect a capacitor (3.3[µF]) between this terminal and GND. This filter is also for ALS circuit.
  • Page 40 SERVICE MANUAL 5. VERTICAL SCAN OUTPUT STAGE CIRCUIT LA78040/LA78041 Both LA78040/LA78041 are vertical scan output stage power amplifiers. But there is a little bit difference between the two amplifiers, that is, LA78040 has supply voltage of 24V and output current of 1.8A while LA78041 has supply voltage of 30V and output current of 2.2A LA78040 /LA78041...
  • Page 41 SERVICE MANUAL 6. EEPROM AT24C04/08/16 1) Features Low-voltage and Standard-voltage Operation -2.7 (Vcc=2.7V to 5.5V) -1.8 (Vcc=1.8V to 5.5V) Internally Organized 128x8(1K), 256x8 (2K), 512x8 (4K), 1024x8 (8K) or 2048x8 (16K) 2-wire Serial Interface Schmitt Trigger, Filtered Inputs for Noise Suppression Bi-directional Data Transfer Protocol 100kHz (1.8V, 2.5V, 2.7V) and 400 kHz (5V) Compatibility Write Protect Pin for Hardware Data Protection...
  • Page 42 SERVICE MANUAL 3) Pin Configuration Table 14 8-lead MAP 8-lead TSSOP Pin Name Function A0-A2 Address Inputs Serial Data Serial Clock Input Write Protect No Connect Bottom View Fig. 19 8-pin PDIP 8-lead SOIC Fig. 20 4) Pin Description SERIAL CLOCK (SCL): The SCL input is used to positive edge clock data into each EEPROM device and negative edge clock data out of each device.
  • Page 43 SERVICE MANUAL protection. The Write Protect pin allows normal read/write operations when connected to ground (GND). When the Write Protect pin is connected to Vcc, the write protection feature is enabled and operates as shown in table 14. Table 15 WP Pin Part of the Array Protected Status...
  • Page 44 SERVICE MANUAL 7. HEF4053BP TRIPLE 2-CHANNEL ANALOG MULTIPLEXER/DEMULTIPLEXER 1). Description The HEF4053 is a triple 2-channel analog multiplexer/demultiplexer with a common enable input (E). Each multiplexer/demultiplexer has two independent inputs/outputs (Y and Y ), a common input/output (Z), and select inputs (Sn). Each also contains two-bidirectional analog switches, each with one side connected to an independent input/output (Y and Y ) and the other side connected to a common...
  • Page 45 SERVICE MANUAL 3) Function Table Table 16 Inputs Channel On none Notes H=HIGH state （the more positive voltage） L=LOW state （the less positive voltage） X=STATE is immaterial 4) Refer to Table 24 about Functions and Data of the IC’s Pins.
  • Page 46 SERVICE MANUAL 8. SWITCH-MODE POWER SUPPLY IC STRG5653/G8656 1). General Description The STRG5653/G8656 are part of the STRG5600/G8600 series thick-film ICs for switch-mode power supply incorporating power MOSFET with a high-precise error amplifier. The ICs feature fewer external components, small-size and standard power supply. The series STR-G8600 use Chip on Chip technology with the same operation principle as STR-G5600.

  • Page 47: Service Data Of Key Ics

    SERVICE MANUAL SERVICE DATA OF KEY ICS Table 18 Ground Resistance of TMPA8801PSBNG Pins Pin No 31.70KΩ 31.70 KΩ 42.87 KΩ 5.5 KΩ 44.25 KΩ Resistance Pin No 44.31 KΩ 17.56 KΩ 39.79 KΩ Resistance Pin No 0.66 KΩ 39.81 KΩ 39.85 KΩ...
  • Page 48 SERVICE MANUAL Table 19 Operating Voltage of TMPA8801PSBNG (N201)’s Pins Pin No 5.2V 2.3V Voltage (V) Pin No 2.3V Voltage (V) Pin No 1.6V 4.2V 4.8V 8.4V 2.0V Voltage (V) Pin No 2.4V 2.4V 2.4V 2.3V Voltage (V) Pin No 3.4V 2.4V 4.8V...
  • Page 49 SERVICE MANUAL Table 20 Functions and Service Data of TDA8944J’s Pins Digital Multimeter Functions Description Reference Voltage Positive Resistance Negative Resistance (20KΩ) (20KΩ) Negative loudspeaker terminal 1 7.98 ∞ ∞ Ground channel 1 Supply voltage channel 1 14.9 Positive loudspeaker terminal 1 ∞...
  • Page 50 SERVICE MANUAL φ5 Lch input Rch input Bias filter Bass LPF (R) Treble HPF (R) Wch output Rch output Treble HPF (L) Bass LPF (L) Lch output Woofer LPF 1 Woofer LPF 2 Woofer LPF 3 Volume filter Woofer LPF 1464 1464 Table 22 Functions and Service Data of LA78040/78041’s Pins...
  • Page 51 SERVICE MANUAL Table 23 Functions and Service Data of AT24C08/16 Pins Digital Multimeter Pin No. Function Description Reference Voltage Positive Resistance Negative Resistance (20KΩ) (20KΩ) Address input 0.001 0.00 Address input 0.001 0.00 Address input 0.001 0.00 (Continued) Common ground 0.001 0.00 Clock line...
  • Page 52 SERVICE MANUAL Table 25 Functions and Service Data of STR-G5653’s Pins Digital Multimeter Functions Description Reference Voltage Positive Resistance Negative Resistance (20KΩ) (20KΩ) Drain terminal 146.3 ∞ ∞ Source terminal Ground terminal Power supply terminal 31.96 ∞ ∞ Overcurrent/Freedback 1.72 0.699 0.166 terminal...

  • Page 53: Replacement Of Parts

    SERVICE MANUAL REPLACEMENT OF PARTS 1. DESCRIPTION Many electrical and mechanical components in this chassis have special safety-related characteristics. Components which have these special safety characteristics in this manual and its supplements are identified by the international hazard symbols or UL, FCC, FDA or VDE marking on the circuit diagram and parts list.
  • Page 54 Circuit Diagram This circuit diagram is only for reference, specifications are subject to change without reference. Which have the same characteristics as original parts. Cold ground Hot ground 1. Any components identified by have special safety-related characteristics. Use replacement...
  • Page 55 PRINTED CIRCUIT BOARD LAYOUT (1)
  • Page 56 PRINTED CIRCUIT BOARD LOYOUTS (2)
  • Page 57 Final Assembly Diagram for 21BM91 *400 Cover board QA pass Warning label Fragile label Wire clip A Binding wire XJ-100 Tapping screw 4X20BAHCh Tapping screw 3X12VwAHCh Tapping screw 3X10KTHCh Notched nut M5 Washer T/JU8.949.224 AV plate Rear plate Side AV plate...
  • Page 58 Final Wiring Diagram for 21BM91 Side-set AV PCB Assembly XPK03B Wired Connector XPK03 Wired Connector XS10A Wired Connector XS161 Main PCB Assembly Wired Connector XS10B XS503 Wired Connector XS601 CRT RGB PCB Assembly Wired Connector XS402 XSB06 CRT's Ground Wire...

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