Consumer Electronics and Maintenance (4341107) - Summer 2023 Solution

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Question 1(a) [3 marks]

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Describe maintenance procedure of CCTV.

Answer:

Table: CCTV Maintenance Procedure

Mnemonic: “CCRU: Clean, Check, Record, Update”

Question 1(b) [4 marks]

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List the types of maintenance and explain in brief.

Answer:

Table: Types of Maintenance

graph TD
    A[Maintenance Types] --> B[Preventive]
    A --> C[Corrective]
    A --> D[Predictive]
    A --> E[Condition-based]
    B --> F[Scheduled checks]
    C --> G[Repairs after breakdown]
    D --> H[Data-based forecasting]
    E --> I[Based on equipment condition]

Mnemonic: “PCPC: Prevent, Correct, Predict, Condition”

Question 1(c) [7 marks]

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Explain maintenance and troubleshooting procedure of Washing Machine.

Answer:

Table: Washing Machine Maintenance and Troubleshooting

Regular Maintenance:

• Monthly: Clean detergent drawer and door seal
• Quarterly: Run empty hot cycle with vinegar/cleaner
• Bi-annually: Check hoses for cracks, clean filter

flowchart TD
    A[Problem Detected] --> B{Machine Starts?}
    B -->|No| C[Check Power & Door Lock]
    B -->|Yes| D{Fills with Water?}
    D -->|No| E[Check Water Supply & Inlet Valve]
    D -->|Yes| F{Drains Properly?}
    F -->|No| G[Check Filter & Drain Pump]
    F -->|Yes| H{Excessive Vibration?}
    H -->|Yes| I[Check Load Balance & Shipping Bolts]
    H -->|No| J{Water Leakage?}
    J -->|Yes| K[Check Hoses & Connections]

Mnemonic: “POWER: Power, Observe, Water, Examine, Repair”

Question 1(c OR) [7 marks]

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Explain maintenance and troubleshooting procedure of Digital TV.

Answer:

Table: Digital TV Maintenance and Troubleshooting

Regular Maintenance:

• Weekly: Dust screen carefully with microfiber cloth
• Monthly: Check and tighten cable connections
• Annually: Update firmware if available

flowchart TD
    A[TV Problem] --> B{Powers On?}
    B -->|No| C[Check Power Supply]
    B -->|Yes| D{Picture Visible?}
    D -->|No| E[Check Input Source]
    D -->|Yes| F{Good Reception?}
    F -->|No| G[Check Antenna/Cable]
    F -->|Yes| H{Correct Colors?}
    H -->|No| I[Reset Picture Settings]
    H -->|Yes| J{Remote Working?}
    J -->|No| K[Check Batteries/Sensor]

Mnemonic: “SPIRE: Supply, Picture, Input, Reception, Electronics”

Question 2(a) [3 marks]

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Define: (1) Brightness (2) Luminance (3) Chrominance

Answer:

Table: Key TV Display Terms

Mnemonic: “BLC: Brightness is Light perception, Luminance is Calculated light, Chrominance is Color information”

Question 2(b) [4 marks]

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Draw and explain block diagram of DTH receiver.

Answer:

DTH Receiver Block Diagram:

graph LR
    A[Satellite Dish] --> B[LNB]
    B --> C[Tuner]
    C --> D[Demodulator]
    D --> E[MPEG Decoder]
    E --> F[Video Processor]
    E --> G[Audio Processor]
    F --> H[TV Display]
    G --> I[Speakers]
    J[Smart Card] --> K[Conditional Access Module]
    K --> D
    L[User Interface] --> M[Microcontroller]
    M --> C
    M --> E

Table: DTH Receiver Components

Mnemonic: “SLTDM: Satellite captures, LNB converts, Tuner selects, Demodulator extracts, MPEG decodes”

Question 2(c) [7 marks]

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Draw and explain block diagram of colour TV receiver.

Answer:

Colour TV Receiver Block Diagram:

graph TD
    A[Antenna] --> B[Tuner]
    B --> C[IF Amplifier]
    C --> D[Video Detector]
    D --> E[Video Amplifier]
    D --> F[Sound IF & Detector]
    E --> G[Y Signal Processing]
    E --> H[Chrominance Bandpass]
    H --> I[Chroma Demodulator]
    I --> J[R-Y Signal]
    I --> K[B-Y Signal]
    G --> L[RGB Matrix]
    J --> L
    K --> L
    L --> M[Picture Tube/Display]
    F --> N[Audio Amplifier]
    N --> O[Speaker]
    P[Power Supply] --> B
    P --> C
    P --> E
    P --> H
    P --> N

Table: Colour TV Components and Functions

Mnemonic: “TIVACRL: Tuner tunes, IF amplifies, Video detects, Audio separates, Chrominance demodulates, RGB mixes, Light displays”

Question 2(a OR) [3 marks]

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Write a short note on LED TV.

Answer:

Table: LED TV Technology

Mnemonic: “BEST: Backlighting with LEDs, Energy efficient, Slim design, True colors”

Question 2(b OR) [4 marks]

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Briefly explain the terms: (1) Hue (2) Saturation

Answer:

Table: Color Properties

graph TD
    A[Color Properties] --> B[Hue]
    A --> C[Saturation]
    B --> D[Wavelength of color]
    C --> E[Purity/vividness]
    D --> F[Measured in degrees on color wheel]
    E --> G[Measured in percentage]

Mnemonic: “HS: Hue is the color Shade, Saturation is the color Strength”

Question 2(c OR) [7 marks]

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Explain additive colour mixing using colour circle diagram and Grassman’s law.

Answer:

Table: Additive Color Mixing Principles

Grassman’s Laws:

• Law 1: Any color can be created by mixing three primary colors
• Law 2: The appearance of a color depends only on its tristimulus values
• Law 3: In additive mixing, the tristimulus values add together

graph TD
    A[Additive Color Mixing] --> B[Primary Colors]
    B --> C[Red]
    B --> D[Green]
    B --> E[Blue]
    C --> F[Red + Green = Yellow]
    D --> F
    D --> G[Green + Blue = Cyan]
    E --> G
    E --> H[Blue + Red = Magenta]
    C --> H
    C --> I[Red + Green + Blue = White]
    D --> I
    E --> I

Color Circle Diagram:

Mnemonic: “RGB-CMY-W: Red, Green, Blue make Cyan, Magenta, Yellow, and White”

Question 3(a) [3 marks]

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List wiring and safety instructions for microwave oven.

Answer:

Table: Microwave Oven Wiring and Safety Instructions

Mnemonic: “POWER: Proper Outlet, Wiring check, Empty operation avoided, Repairs by professionals”

Question 3(b) [4 marks]

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Explain working of Air conditioner.

Answer:

Table: Air Conditioner Working Cycle

flowchart LR
    A[Compressor] -->|High-pressure gas| B[Condenser]
    B -->|Liquid| C[Expansion Valve]
    C -->|Low-pressure liquid| D[Evaporator]
    D -->|Low-pressure gas| A
    E[Room Air] --> D
    D --> F[Cool Air]
    G[Outside Air] --> B
    B --> H[Hot Air]

Mnemonic: “CELT: Compress gas, Expel heat, Lower pressure, Take in heat”

Question 3(c) [7 marks]

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Explain electronic controller for washing machine and fuzzy logic washing machine. Also list technical specifications of washing machine.

Answer:

Table: Electronic Controller in Washing Machines

Fuzzy Logic in Washing Machines:

• Uses artificial intelligence for optimal washing
• Adjusts water level, wash time, and spin speed based on load
• Makes decisions using approximate reasoning instead of precise values
• Adapts to different fabric types and soil levels automatically

Technical Specifications:

• Capacity: 6-10 kg (front load), 5-8 kg (top load)
• Energy Rating: A+++ to B (EU standards)
• Water Consumption: 40-70 liters per cycle
• Spin Speed: 800-1600 RPM
• Cycle Options: 8-16 programs

graph TD
    A[Electronic Controller] --> B[Microcontroller]
    B --> C[Sensor Inputs]
    B --> D[User Interface]
    B --> E[Actuator Control]
    C --> F[Water Level Sensor]
    C --> G[Temperature Sensor]
    C --> H[Load Balance Sensor]
    C --> I[Door Lock Sensor]
    E --> J[Motor Driver]
    E --> K[Water Valve Control]
    E --> L[Drain Pump Control]
    E --> M[Heater Control]
    N[Fuzzy Logic] --> B
    N --> O[Adaptive Control]
    O --> P[Water Level Adjustment]
    O --> Q[Wash Time Optimization]
    O --> R[Spin Speed Adjustment]

Mnemonic: “SCRAM: Sensors detect, Controller processes, Rules applied, Actuators operate, Machine adapts”

Question 3(a OR) [3 marks]

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State main components of solar power system and specifications of solar power system.

Answer:

Table: Solar Power System Components

Specifications:

• Panel Capacity: 250-400 Watts per panel
• System Size: 1-10 kW (residential)
• Battery Capacity: 100-200 Ah
• Inverter Efficiency: 90-97%
• Expected Lifespan: 25-30 years (panels)

Mnemonic: “PIBCM: Panels collect, Inverter converts, Batteries store, Controller protects, Mounts support”

Question 3(b OR) [4 marks]

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Explain working of Refrigerator.

Answer:

Table: Refrigerator Working Cycle

flowchart TD
    A[Compressor] -->|High-pressure gas| B[Condenser]
    B -->|Heat released outside| C[High-pressure liquid]
    C --> D[Expansion Valve]
    D -->|Sudden pressure drop| E[Low-pressure liquid]
    E --> F[Evaporator]
    F -->|Heat absorbed from inside| G[Low-pressure gas]
    G --> A
    H[Thermostat] --> A

Mnemonic: “CEHE: Compress gas, Expel heat, Halve pressure, Extract heat”

Question 3(c OR) [7 marks]

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Draw and explain block diagram of Microwave oven. List types, applications and technical specifications of microwave oven.

Answer:

Microwave Oven Block Diagram:

graph TD
    A[Power Supply] --> B[Control Panel/Timer]
    A --> C[High Voltage Transformer]
    B --> D[Door Interlock Switches]
    B --> E[Control Circuit/Microcontroller]
    E --> F[Magnetron Driver]
    C --> F
    F --> G[Magnetron]
    G --> H[Waveguide]
    H --> I[Cooking Cavity]
    E --> J[Turntable Motor]
    J --> K[Turntable]
    E --> L[Cooling Fan]

Types of Microwave Ovens:

• Solo: Basic heating and defrosting only
• Grill: Has additional grilling element
• Convection: Combines microwave with convection heating
• Over-the-Range (OTR): Includes ventilation system
• Built-in: Designed for cabinet installation

Applications:

• Cooking: Fast meal preparation
• Reheating: Leftover foods
• Defrosting: Frozen foods
• Sterilization: Small items
• Commercial: Food service industry

Technical Specifications:

• Capacity: 20-40 liters
• Power Output: 700-1200 watts
• Power Consumption: 1100-1500 watts
• Frequency: 2.45 GHz
• Voltage: 220-240V AC

Mnemonic: “MICROWAVES: Magnetron generates, Interior receives, Control regulates, Rotating turntable, Oven cavity, Waveguide directs, Alternating current powers, Ventilation cools, Electronic timer, Safety interlocks”

Question 4(a) [3 marks]

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List specifications of MF printer and LCD projector.

Answer:

Table: Multi-Function Printer Specifications

Table: LCD Projector Specifications

Mnemonic: “PSCPL: Print resolution, Speed, Connectivity, Projection brightness, Lamp life”

Question 4(b) [4 marks]

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Draw block diagram of Inkjet printer and explain its working in brief.

Answer:

Inkjet Printer Block Diagram:

graph TD
    A[Power Supply] --> B[Control Board/CPU]
    B --> C[Paper Feed Motor]
    B --> D[Printhead Motor]
    B --> E[Printhead Controller]
    E --> F[Ink Cartridges]
    F --> G[Printhead Nozzles]
    B --> H[Input Interface]
    I[Computer] --> H
    C --> J[Paper Feed Mechanism]
    D --> K[Carriage Assembly]
    K --> F
    B --> L[Sensors]
    L --> M[Paper Sensors]
    L --> N[Ink Level Sensors]

Working of Inkjet Printer:

1. Document Processing: Control board receives data and converts to printer commands
2. Paper Loading: Feed motor pulls paper from tray
3. Printing: Printhead moves across paper while ejecting tiny ink droplets
4. Droplet Formation: Thermal or piezoelectric method forces ink droplets onto paper
5. Paper Advancement: Paper advances line by line until printing completes

Mnemonic: “PIPES: Paper feeds, Ink ejects, Printhead moves, Electronic control, Sheet advances”

Question 4(c) [7 marks]

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Explain working of Photocopier with block diagram and list its specifications.

Answer:

Photocopier Block Diagram:

graph TD
    A[Control Panel] --> B[Main Control Board]
    B --> C[Scanning System]
    C --> D[Light Source]
    C --> E[Mirrors and Lenses]
    C --> F[CCD/Image Sensor]
    B --> G[Imaging System]
    G --> H[Photosensitive Drum]
    G --> I[Charging Corona]
    G --> J[Developing Unit]
    G --> K[Transfer Corona]
    G --> L[Fusing Unit]
    B --> M[Paper Feed System]
    M --> N[Paper Trays]
    M --> O[Feed Rollers]
    M --> P[Registration Rollers]
    B --> Q[Power Supply]

Working of Photocopier:

1. Charging: Photosensitive drum receives uniform electrostatic charge
2. Exposure: Original document scanned, creating light pattern on drum
3. Developing: Toner particles attracted to charged areas on drum
4. Transfer: Toner image transferred from drum to paper
5. Fusing: Heat and pressure melt toner permanently onto paper
6. Cleaning: Drum cleaned for next cycle

Technical Specifications:

• Speed: 20-60 pages per minute
• Resolution: 600-1200 dpi
• Paper Capacity: 250-2000 sheets
• Maximum Paper Size: A3/11×17 inches
• Zoom Range: 25-400%
• Memory: 512MB-2GB
• Connectivity: Ethernet, USB, Wi-Fi

Mnemonic: “CETFC: Charge drum, Expose image, Transfer toner, Fuse permanently, Clean drum”

Question 4(a OR) [3 marks]

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Write a short note on CCTV.

Answer:

Table: CCTV System Overview

Key Applications:

• Security monitoring of buildings
• Traffic monitoring
• Retail loss prevention
• Public area surveillance
• Home security

Mnemonic: “SCRAM: Security monitoring, Closed circuit, Recording footage, Access restricted, Monitoring continuous”

Question 4(b OR) [4 marks]

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Explain working of LCD projector with block diagram.

Answer:

LCD Projector Block Diagram:

graph TD
    A[Power Supply] --> B[Control Circuit]
    B --> C[Lamp/Light Source]
    C --> D[Cooling System]
    C --> E[Reflector]
    E --> F[Condenser Lens]
    F --> G[Dichroic Mirrors]
    G -->|Red| H[Red LCD Panel]
    G -->|Green| I[Green LCD Panel]
    G -->|Blue| J[Blue LCD Panel]
    H --> K[Combining Prism]
    I --> K
    J --> K
    K --> L[Projection Lens]
    L --> M[Screen]
    B --> N[Input Interfaces]
    B --> O[Keystone Correction]
    B --> P[Focus Control]

Working of LCD Projector:

1. Light Generation: High-intensity lamp produces white light
2. Color Separation: Dichroic mirrors split light into RGB components
3. Image Formation: LCD panels modulate light based on input signal
4. Recombination: Prism combines RGB images into full-color image
5. Projection: Lens system projects final image onto screen

Mnemonic: “LSCIP: Light source generates, Split into colors, Control with LCDs, Image combined, Projected on screen”

Question 4(c OR) [7 marks]

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Explain working of laser printer with block diagram.

Answer:

Laser Printer Block Diagram:

graph TD
    A[Control Board] --> B[Laser Diode]
    A --> C[Polygon Mirror Motor]
    B --> D[Polygon Mirror]
    D --> E[Focusing Lenses]
    E --> F[Photosensitive Drum]
    A --> G[Primary Corona]
    G --> F
    A --> H[Developer Unit]
    H --> F
    A --> I[Transfer Corona]
    I --> F
    A --> J[Fusing Unit]
    A --> K[Paper Feed Mechanism]
    K --> L[Paper Path]
    L --> J
    A --> M[Power Supply]
    A --> N[Interface]

Laser Printing Process:

Table: Six Steps of Laser Printing

Technical Specifications:

• Print Speed: 20-50 ppm
• Resolution: 600-2400 dpi
• Memory: 128MB-1GB
• Duty Cycle: 10,000-150,000 pages/month
• Connectivity: USB, Ethernet, Wi-Fi

Mnemonic: “CCWDTF: Clean drum, Charge uniformly, Write with laser, Develop with toner, Transfer to paper, Fuse permanently”

Question 5(a) [3 marks]

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Define: (1) Pitch (2) Reverberation (3) Microphone.

Answer:

Table: Audio Terminology

Mnemonic: “PRM: Pitch is frequency, Reverberation is reflection, Microphone is converter”

Question 5(b) [4 marks]

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Draw and explain block diagram of PA system.

Answer:

PA System Block Diagram:

graph LR
    A[Microphone] --> B[Pre-amplifier]
    B --> C[Mixer]
    D[Audio Source] --> C
    E[Equalizer] --> C
    C --> F[Power Amplifier]
    F --> G[Speaker System]
    H[Control System] --> C
    H --> F

Table: PA System Components

Mnemonic: “MPMEPA: Microphone Picks, Preamp Magnifies, Equalizer adjusts, Power Amplifier drives, Audience hears”

Question 5(c) [7 marks]

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Explain Crystal microphone.

Answer:

Table: Crystal Microphone Characteristics

Working Principle: When sound waves strike the diaphragm, they create pressure on the crystal element. Due to the piezoelectric effect, the crystal generates a voltage proportional to the mechanical stress. This voltage is the electrical representation of the sound.

graph TD
    A[Sound Waves] --> B[Diaphragm]
    B --> C[Mechanical Stress on Crystal]
    C --> D[Piezoelectric Effect]
    D --> E[Voltage Generation]
    E --> F[Electrical Output]

Applications:

• Telephone receivers
• Contact pickups for acoustic instruments
• Low-cost recording devices
• Public address systems

Advantages and Limitations:

Mnemonic: “PIES: Pressure applied, Impedance high, Electricity generated, Sound converted”

Question 5(a OR) [3 marks]

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Draw block diagram of Home theatre sound system.

Answer:

Home Theatre Sound System Block Diagram:

graph TD
    A[Audio/Video Source] --> B[AV Receiver/Amplifier]
    B --> C[Front Left Speaker]
    B --> D[Center Speaker]
    B --> E[Front Right Speaker]
    B --> F[Surround Left Speaker]
    B --> G[Surround Right Speaker]
    B --> H[Subwoofer]
    I[Remote Control] --> B
    J[TV/Display] --> B
    B --> J
    K[Streaming Module] --> B

Mnemonic: “SAVS: Source provides, Amplifier processes, Various speakers deliver, Surround experience created”

Question 5(b OR) [4 marks]

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Explain optical sound recording.

Answer:

Table: Optical Sound Recording Process

Types of Optical Sound Tracks:

• Variable Density: Light intensity varies (darker/lighter areas)
• Variable Area: Transparent area width varies against opaque background

graph TD
    A[Sound Input] --> B[Microphone]
    B --> C[Amplifier]
    C --> D[Light Modulator]
    E[Light Source] --> D
    D --> F[Optical System]
    F --> G[Moving Film]
    H[Developed Film] --> I[Playback Light Source]
    I --> J[Photocell/Detector]
    J --> K[Amplifier]
    K --> L[Speaker]

Mnemonic: “CAREP: Capture sound, Amplify signal, Record optically, Expose film, Play back”

Question 5(c OR) [7 marks]

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Define loudspeaker. List types of loudspeakers and explain working of any one type of loudspeaker.

Answer:

Definition: A loudspeaker is an electroacoustic transducer that converts electrical signals into sound waves by moving a diaphragm that creates air pressure variations.

Table: Types of Loudspeakers

Working of Dynamic/Moving Coil Loudspeaker:

graph TD
    A[Audio Signal] --> B[Voice Coil]
    B --> C[Electromagnetic Field]
    D[Permanent Magnet] --> C
    C --> E[Movement of Voice Coil]
    E --> F[Cone/Diaphragm Movement]
    F --> G[Air Pressure Variations]
    G --> H[Sound Waves]

Working Process:

1. Audio current flows through voice coil
2. Current creates electromagnetic field
3. Electromagnetic field interacts with permanent magnet
4. Voice coil moves forward/backward based on signal polarity
5. Attached cone/diaphragm moves, creating air pressure variations
6. Air pressure variations propagate as sound waves

Components:

• Cone/Diaphragm: Moves air to create sound
• Voice Coil: Carries audio signal current
• Magnet: Creates static magnetic field
• Suspension: Keeps cone centered, allows movement
• Frame/Basket: Holds components in proper alignment

Mnemonic: “SEPVADICS: Signal Enters, Produces Vibrations, Activates Diaphragm, In Coordination with Suspension”