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AFT and remote control Circuits

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  1. AFT and remote control Circuits

  2. Importance of AFC • Receivers that have provisions for remote tinning have no provision for remote fine tuning • Color receivers that have provisions for remote tuning to obtain the best color reproduction • Many customers found it difficult to adjust the manual fine tuning control property • A very slight drift in the frequency of the tuner oscillator causes a loss of color picture quality

  3. AFT Section

  4. Troubleshooting AFT circuits • Weak or no AFT performance • No picture no sound raster ok • Large tuning error • Moment to moment picture variations

  5. Ultrasound remote control

  6. Causes of AFT problems • A defective transistor or associated circuits • A defective transformer • defective IC or associated circuits such as an open coil • Misalignment of the AFT tuned circuits • Incorrect power supply voltage • Defective varactor • Incorect varactor voltage

  7. AFT circuit that uses dc amplifier to drive the varactor

  8. Large tuning error on channels that originates form the varactor • DC amplifier balance change caused by the change in resistor anywhere in the DC amplifier • Defective varactor

  9. Remote control Capability • Change channel • Adjust volume • Adjust picture • Adjust contrast • Adjust sharpness • Sound quality adjustment • Power switch

  10. Remote controls • Ultrasonic Transmitter • Acoustic transmitter • Function by tune signals from receiver to transmitter

  11. Ultrasound remote control

  12. Kinds of remote control faults • Weak intensive response on all function • Dead all function • Dead on some function but not all

  13. Electronic memory remote control • Producing ultrasonic sound through electronic circuit controlled system.

  14. Three tone remote control

  15. Infrared system • Using invisible infrared signal • Digitally modulated infrared signal 42 KHz sensed by infrared diodes.

  16. Infrared remote control

  17. AFT discriminator circuit

  18. AFT Circuit

  19. Receiver

  20. Transmitter

  21. Multifunction Remote Control

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