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IDENTIFYING THE FAULTY STAGE,Audio & video system

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troubleshooting in audio & video

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IDENTIFYING THE FAULTY STAGE,Audio & video system

  1. 1. AUDIO & VIDEO System IDENTIFYING THE FAULTY STAGE Presented by: PRANAV VEERANI (130280111117) Submitted to : PROFESSOR PRATIK GIRI GOSWAMI
  2. 2. IDENTIFYING THE FAULTY STAGE Stages are connected in four types of circuit configurations: 1.Sequential stages 2.Divergent circuits 3.Convergent circuits 4.Closed loop(feedback) circuits
  3. 3. SEQUENTIAL STAGES There are three method of this stage .  Stages are in series one after the other. 1.Signal Injection & Tracing 2.Signal substitution 3.Short circuiting the input
  4. 4. SEQUENTIAL STAGES 1.Signal injection & tracing : In this method signal is injected at the input of the system & its presence is detected by signal tracer at different stages. Signal tracing can be done by a diode tracer, or a cathode ray oscilloscope(CRO). 2.Signal substitution : In this method , Signal is given at the inputs of different stages & the final output is checked. 3.Short circuiting the inputs : One by one for locating the source of noise(like self oscillations).
  5. 5. SEQUENTIAL STAGES In sequential circuit , the quickest method of finding out which stage is faulty is split half method . Split Half Method : In this method , the output at a stage in the middle of the sequential stages is checked. If it is correct, the first half of the stages is alright & the defect lies in the second half. Then, the output at the middle stage of the second half is checked to find out which portion is defective & so on ,until we reach at the correct stage . Figure of this method is shown below:
  6. 6. SEQUENTIAL STAGES Split Half Method
  7. 7. DIVERGENT CIRCUITS  The circuit which has one input path , but the output takes several paths is called divergent circuit. One such circuit of power supply output , which sends power to several stages from its output point.( )
  8. 8. DIVERGENT CIRCUITS Several loudspeakers connected to one output of final power amplifier stage.(1) Switching circuit with one input and several output.(2) DE multiplexer circuit which receives one input but gives several outputs.(3) Video detector input is one but there are several outputs, like sound section, luminance , chroma and raster sections.(4)
  9. 9. DIVERGENT CIRCUITS 1 2 3 4
  10. 10. CONVERGENT CIRCUITS The circuit which has several input but only one output is called convergent circuit. Mixer stage for microphone in the PA system in which several microphone are connected in the input and there is only one output for feeding to the amplifier(1) 1
  11. 11. CONVERGENT CIRCUITS • Multiplexer which takes several signals in its input and gives out only one signal.(2) • Logic gates(except NOT gate) which give one output for two or more input.(3) • Switching circuit with several inputs and one output.(4) 2 3 4
  12. 12. CONVERGENT CIRCUITS Fault diagnosis in convergent circuits will also be done in the same way as in divergent circuits . Each input circuit will be isolated to find the output . If expected output is obtained after isolating a circuit in the input, than that circuit is faulty.
  13. 13. CLOSED LOOPCIRCUITS Feedback circuits from a closed loop. Negative feedback(1) Servo controlled devices(2) Positive feedback(3) Automatic gain control(4)
  14. 14. CLOSED LOOPCIRCUITS 1 2 3 4
  15. 15. FAULTY COMPONENT • Faulty component in the Faulty Stage: 1.Measurement of resistance, dc voltage and ac signal voltage at the specified test points. 2.Substitution of the suspected component by a good one.  Passive and active components may become open or leaky or short. The causes for components to become faulty are many . But voltage fluctuation, transients , dust , temperature variation , grease between tracks of PCB, dry or cold solder joints, vibrations/shocks, mishandling , expiry of life ,etc. are the most common causes for failures.  Dust is the biggest enemy of an electronic equipment because it prevents radiation of heat from the ICs and other components.
  16. 16. FAULTY COMPONENT Some common faults: Resistor(open) Capacitor(open , short , leaky) Inductor(open , short) Transformer(leaky) Diode(open , short) Transistor(open , short , leaky)
  17. 17. FAULTY COMPONENT Common faults in PCB: 1.Solder bridge between adjacent tracks 2.Pin holes 3.Break in plated through hole(PTH) 4.Loose connection in connectors 5.Dry or cold solder joint
  18. 18. REFERENCE AUDIO AND VIDEO ENGINEERING SYSTEMS BY R G GUPTA
  19. 19. THANK YOU

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