This document outlines the operational, maintenance, and technical specifications for a television receiver, specifically model CTR-1498EMK. It covers various aspects from safety precautions and general adjustments to detailed circuit diagrams and parts lists, providing a comprehensive guide for servicing and understanding the device.
Function Description:
The CTR-1498EMK is a television receiver designed to display video and audio signals. It incorporates standard TV reception capabilities and features for adjusting picture quality, color, and sound. The device includes an automatic degaussing function to maintain color purity, and various controls for user interaction, such as volume, channel selection, and picture adjustments. It supports both B/G and D/K television systems, indicating its adaptability to different broadcast standards. The receiver also features an infrared remote sensor for remote control operation and includes audio/video input terminals for connecting external devices.
Important Technical Specifications:
- Power Supply: The receiver operates with a 220V (50Hz) AC mains power source. The internal B+ voltage is set at +110V.
- High Voltage: The normal high voltage at zero beam current (minimum brightness) is 25kV. This voltage must not exceed 26kV under any circumstances to prevent X-ray radiation hazards. The device is equipped with an X-RAY RADIATION circuit that sets the receiver to STAND BY mode if the high voltage reaches a set value, preventing excessive X-RAY RADIATION.
- Sound Carrier Frequency: For the D/K system, the sound carrier frequency is 6.5MHz. For the B/G system, the sound carrier frequency is 5.5MHz.
- Video Carrier Frequency: For the D/K system, the video carrier frequency is 38.0MHz. For the B/G system, the video carrier frequency is 38.9MHz.
- AGC Voltage: The AGC voltage should be 6.2V after adjustment.
- Power Supply Circuit: The power supply circuit is a "HOT" chassis design, while the rest of the chassis is "COLD." This distinction is critical for safety during servicing.
Usage Features:
- Controls: The front panel includes controls for volume (up/down), channel selection (up/down), a power switch, an LED indicator, and an infrared remote sensor. A control door hides additional controls such as manual tuning, auto preset, stand by, preset on/off, and skip functions.
- Connectivity: The receiver provides antenna terminals for RF input and audio/video input terminals for connecting external devices like VCRs or DVD players.
- Automatic Degaussing: An automatic degaussing coil is attached around the picture tube. This system degausses the tube approximately one second after the set is switched on. If the receiver is moved or faced in a different direction, the power must be switched off for at least 15 minutes for the automatic degaussing circuit to operate properly.
- Picture Adjustments: Users can adjust brightness, contrast, color, and tint. Specific controls are available for horizontal and vertical hold, height, and picture center position.
- OSD Position Adjustment: The OSD (On-Screen Display) position can be adjusted using control C816 to ensure the caption display appears in the upper right corner of the screen.
- Color Bar Pattern: The device supports tuning in a color bar pattern signal for various adjustments, including ABL, color sync, and PAL/SECAM color decoder adjustments.
Maintenance Features:
- Safety Precautions:
- An isolation transformer should be used during any dynamic service due to the "HOT" chassis design.
- The picture tube anode must always be discharged before handling the picture tube.
- Shatter-proof goggles should be worn when handling the picture tube.
- All protective devices (non-metallic control knobs, insulating covers, shields, isolation resistor-capacitor network) must be put back in place after servicing.
- The power cord must be disconnected when replacing parts or circuit boards.
- High voltage resistors (oxide metal film resistors) should be kept 10mm (1/2in) away from the circuit board.
- Connection wires must be kept away from high voltage or high-temperature components.
- Fuses must be replaced with the exact type specified in the chassis parts list.
- Special safety-related parts are identified in the manual (shaded on schematic diagrams and parts lists) and must be replaced with components having the same safety characteristics.
- General Adjustment Instruction:
- Adjustments require exact procedures and should only be undertaken when necessary.
- Specified test equipment or its equivalent is required for proper alignment.
- The AC power line voltage should be maintained at 215 to 225 volts 50Hz during alignment.
- Do not connect or disconnect wires while the receiver is in operation.
- Allow the receiver to warm up for at least 10 minutes before making adjustments, unless otherwise noted.
- Low voltage DC supply should be used for safety during adjustments.
- Picture I.F. and Sound I.F. Alignment: Detailed procedures are provided for aligning the Picture I.F. (Intermediate Frequency) and SIF (Sound Intermediate Frequency) using a sweep/marker generator, oscilloscope, and DC power supply. This includes adjusting coils L105, L109, L110, and L108 to achieve specific waveform responses and maximum amplitude signal output with minimum distortion.
- White Balance Adjustment: This involves setting brightness and contrast, adjusting R.G.B. cut-off controls (VR403, VR404, VR405) and B.G. drive controls (VR401, VR402) to achieve a good white balance at both low and high luminance.
- Color Purity and Convergence Adjustment:
- Color Purity: Involves degaussing the picture tube, adjusting red and blue controls to provide a green raster, loosening the yoke clamp screw, rotating and spreading purity magnets, and moving the yoke to obtain uniform green, red, and blue rasters.
- Convergence: Requires adjusting 4-pole and 6-pole magnets to superimpose red, blue, and green vertical and horizontal lines in the center area and circumference of the screen. This process often involves using rubber wedges and grass cloth tapes to hold the yoke in position.
- PAL/SECAM Decoder Adjustments: Specific procedures are outlined for PAL matrix adjustment, SECAM ident filter adjustment, BELL filter adjustment, and B-Y/R-Y demodulation, involving the use of an oscilloscope, DC voltmeter, and color bar signals to ensure correct color output and signal waveforms.
- Parts Lists and Diagrams: The manual includes a wiring diagram, schematic diagram, block diagram, electrical parts list, exploded view, and mechanical parts list, which are essential resources for identifying components and troubleshooting. Special safety-related parts are shaded in the schematic diagram and parts list to highlight their importance.
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