This set of Audio Video Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Troubleshooting – Fault Actions, Shielding and Grounding”.
1. The purpose of shielding is to increase noise currents from coupling into electrical measurements.
a) True
b) False
View Answer
Explanation: The above statement is false. A shield is a barrier of conducting material kept in a path of unwanted signals. The instruments which are used for measuring perimeters of components or devices should be shielded properly so it does not get affected by noise or interference. The purpose of shielding is to reduce or eliminate noise current from coupling into electrical measurements.
2. How many types of interfering fields are there?
a) 1
b) 3
c) 4
d) 2
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Explanation: The interfering fields are of two types:
i) Electric field
ii) Magnetic field
Static magnetic field uses non-magnetic conductor like aluminum. Magnetic field uses ferromagnetic material like iron.
3. How much percent of the problems are related to ground in wiring of an audio system?
a) 90
b) 50
c) 70
d) 30
View Answer
Explanation: A ground line in the PCB is connected to an effective earth line through a cold water pipe or by an artificial earth terminal. Probably 90% of the problems encountered in wiring an audio system are related to ground. Indications of ground trouble include humming, weak signal, radio interference, crackling noises and electric shocks.
4. In many circuits, the current return path is designated as ground.
a) True
b) False
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Explanation: If there is a wire carrying current from one device to another, there has to be a second wire for the current to flow back. When an equipment is designed for balanced connections, there is a second wire inside the cable for the current to flow back. In many circuits, the current’s return path is designated as ground.
5. Which of the following is not the type of circuit configuration when the stage is faulty?
a) Subsequent stage
b) Dissimilar circuits
c) Merging circuits
d) Section stage
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Explanation: Stages are basically connected in four types of circuit configurations: a) Subsequent stages b) Dissimilar circuits c) Merging circuits d) Feedback (Closed loop) circuits. We can identify the faulty component using the following methods:
i) Measuring resistance, dc and ac voltage at the specified test points.
ii) Replacing the component expected to be faulty by a better one.
6. Which type of circuit has only one output but many different inputs?
a) Subsequent stage
b) Dissimilar circuits
c) Merging circuits
d) Feedback circuits
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Explanation: Merging circuits has only one output but many different inputs. Examples of merging circuits are mixer stage for microphone, multiplexer, logic gates and switching circuit. In this case, the fault diagnosis is done in the same manner similar to dissimilar circuits. Each input circuit in convergent circuit is isolated to find out whether the output stage is faulty or not.
7. Which of the following circuit block diagram is shown in the below figure?
a) Feedback circuit
b) Merging circuit
c) Dissimilar circuit
d) Subsequent circuit
View Answer
Explanation: Closed-loop (Feedback) circuit is shown in the figure. Feedback circuits form a closed loop. In the figure the circuit is forming a closed loop. If the fault is present at any one point it will be present in the whole circuit. For such fault diagnosis, the best method is to isolate the feedback circuit, and then expect distorted and higher output signal for -ve feedback and no signal for +ve feedback.
Sanfoundry Global Education & Learning Series – Audio Video Engineering.
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