Consumer Electronics & Maintenance (4341107) - Winter 2023 Solution

Question 1(a) [3 marks]

#

Explain different types of maintenance in brief.

Answer:

Mnemonic: “PCPro” - Preventive prevents, Corrective cures, Predictive predicts

Question 1(b) [4 marks]

#

Explain maintenance procedure of Washing Machine.

Answer:

Maintenance Procedure for Washing Machine:

flowchart TD
    A[Regular Inspection] --> B[Clean Filter]
    B --> C[Check Hoses]
    C --> D[Balance Load]
    D --> E[Clean Drum]

• Filter Cleaning: Remove and clean lint filter monthly
• Hose Inspection: Check for cracks and leaks every 3 months
• Load Distribution: Ensure proper balancing to prevent vibration
• Drum Cleaning: Run empty hot water cycle with vinegar quarterly

Mnemonic: “FHLD” - Filters, Hoses, Loads, Drum need regular attention

Question 1(c) [7 marks]

#

Explain maintenance and troubleshooting procedure of Microwave Oven.

Answer:

Maintenance and Troubleshooting for Microwave Oven:

Troubleshooting Procedure:

flowchart TD
    A[No Power] -->|Check| B[Power Connection]
    C[Not Heating] -->|Check| D[Door Switch & Magnetron]
    E[Uneven Cooking] -->|Check| F[Turntable Mechanism]
    G[Sparking] -->|Check| H[Metal Objects/Damaged Cavity]
    I[Unusual Noise] -->|Check| J[Fan & Turntable Motor]

• Power Issues: Check fuse, circuit breaker, and cord
• Heating Problems: Test door switch, high voltage capacitor, magnetron
• Safety First: Never operate with damaged door or seals

Mnemonic: “POWER” - Power, Oven interior, Wiring, Electronics, Radiation seals

Question 1(c OR) [7 marks]

#

Explain maintenance and troubleshooting procedure of projector.

Answer:

Maintenance and Troubleshooting for Projector:

Troubleshooting Procedure:

flowchart TD
    A[No Power] -->|Check| B[Power Supply & Cable]
    C[No Image] -->|Check| D[Source Connection & Input Selection]
    E[Poor Image] -->|Check| F[Focus & Lens]
    G[Overheating] -->|Check| H[Ventilation & Filters]
    I[Lamp Failure] -->|Check| J[Lamp Life & Replacement]

• Image Issues: Adjust focus, resolution, keystone correction
• Lamp Problems: Check lamp hours, replace if exceeding limit
• Connectivity: Verify input source and cable connections
• Thermal Issues: Clean filters and ensure proper ventilation

Mnemonic: “FLAMVE” - Filters, Lamp, Airflow, Mounting, Voltage, Environment

Question 2(a) [3 marks]

#

Explain the terms in brief: (1) Hue (2) Brightness

Answer:

Diagram:

Mnemonic: “HB-WC” - Hue determines What Color, Brightness determines White-to-black level

Question 2(b) [4 marks]

#

Write a short note on LCD TV.

Answer:

LCD TV Technology:

flowchart LR
    A[Backlight] --> B[Polarizing Filter]
    B --> C[Liquid Crystal Layer]
    C --> D[Color Filter]
    D --> E[Screen]

• Working Principle: Uses liquid crystals that twist/untwist to allow/block light
• Key Components: Backlight, polarizing filters, liquid crystal matrix, color filters
• Advantages: Thin profile, energy efficient, no radiation, sharp image
• Limitations: Limited viewing angle, slower response time than newer technologies

Mnemonic: “BPLCS” - Backlight Passes Light through Crystals to Screen

Question 2(c) [7 marks]

#

Draw and explain block diagram of DTH receiver.

Answer:

DTH Receiver Block Diagram:

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

• Satellite Dish: Captures signals from satellite
• LNB (Low Noise Block): Converts high frequency signals to lower frequency
• Tuner: Selects specific channel frequency
• Demodulator: Extracts digital information from carrier signal
• MPEG Decoder: Decompresses video/audio data
• Conditional Access Module: Controls subscription access
• Microcontroller: Controls overall operation and user inputs

Mnemonic: “SLTDMP” - Satellite, LNB, Tuner, Demodulator, MPEG, Processor

Question 2(a OR) [3 marks]

#

Explain the terms in brief: (1) Luminance (2) chrominance

Answer:

Diagram:

Mnemonic: “LC-BH” - Luminance controls Brightness, Chrominance controls Hue

Question 2(b OR) [4 marks]

#

Explain Grassman’s law.

Answer:

Grassman’s Laws of Color Mixing:

• Application: Forms the basis of RGB color model in displays
• Significance: Allows creating any color by mixing three primary colors
• Limitation: Applies only to light (additive mixing), not pigments

Mnemonic: “SPA Color” - Symmetry, Proportionality, Additivity laws for Color matching

Question 2(c OR) [7 marks]

#

Draw and explain block diagram of colour TV receiver.

Answer:

Colour TV Receiver Block Diagram:

flowchart LR
    A[Antenna] --> B[Tuner]
    B --> C[IF Amplifier]
    C --> D[Video Detector]
    D --> E[Video Amplifier]
    E --> F[Color Processor]
    F --> G[RGB Matrix]
    G --> H[Picture Tube/Display]
    D --> I[Sound IF]
    I --> J[Sound Demodulator]
    J --> K[Audio Amplifier]
    K --> L[Speaker]
    M[Sync Separator] --> N[Deflection Circuits]
    N --> H
    D --> M

• Tuner: Selects desired channel frequency
• IF Amplifier: Amplifies intermediate frequency signals
• Video Detector: Extracts video and audio information
• Color Processor: Separates luminance and chrominance
• RGB Matrix: Converts color signals to red, green, blue
• Sync Separator: Extracts horizontal and vertical sync
• Deflection Circuits: Control electron beam scanning

Mnemonic: “TIVCRDS” - Tuner, IF, Video, Color, RGB, Deflection, Speaker

Question 3(a) [3 marks]

#

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

Answer:

Main Components of Solar Power System:

Specifications:

• Panel Rating: 100-400W per panel
• Battery Capacity: 100-200Ah
• Inverter Rating: 500-5000W
• System Voltage: 12/24/48V

Mnemonic: “SCBIM” - Solar panels, Controller, Battery, Inverter, Mounting

Question 3(b) [4 marks]

#

List types, applications and technical specifications of microwave oven.

Answer:

Types of Microwave Ovens:

Applications:

• Food reheating
• Defrosting
• Cooking
• Baking (convection models)

Technical Specifications:

• Power: 700-1200 Watts
• Capacity: 20-40 Liters
• Frequency: 2.45 GHz
• Voltage: 220-240V AC

Mnemonic: “SGCC” - Solo, Grill, Convection, Combo ovens for various cooking needs

Question 3(c) [7 marks]

#

Explain working of Air conditioner and Refrigerator

Answer:

Working Principle of Air Conditioner and Refrigerator:

flowchart TD
    A[Compressor] -->|High pressure hot gas| B[Condenser]
    B -->|High pressure liquid| C[Expansion Valve]
    C -->|Low pressure liquid| D[Evaporator]
    D -->|Low pressure gas| A

Common Components:

• Compressor: Pressurizes refrigerant gas
• Condenser: Releases heat, converts gas to liquid
• Expansion Valve: Reduces pressure of liquid refrigerant
• Evaporator: Absorbs heat, converts liquid to gas

Differences:

Mnemonic: “CEVA” - Compression, Expansion, Vaporization, Absorption cycle

Question 3(a OR) [3 marks]

#

List technical specifications of Air conditioner and Refrigerator

Answer:

Technical Specifications:

Mnemonic: “CPERS” - Capacity, Power, Efficiency, Refrigerant, Supply specifications

Question 3(b OR) [4 marks]

#

Explain electronic controller for washing machine.

Answer:

Electronic Controller for Washing Machine:

flowchart LR
    A[User Interface] --> B[Microcontroller]
    B --> C[Motor Driver]
    B --> D[Water Valve Control]
    B --> E[Temperature Sensor]
    B --> F[Water Level Sensor]
    B --> G[Door Lock Control]
    B --> H[Drain Pump Control]

• Microcontroller: Central processing unit that controls all operations
• Sensors: Water level, temperature, load balance, door position
• Actuators: Motor driver, water valves, heater, drain pump
• User Interface: Program selection, temperature, spin speed settings

Mnemonic: “MIST-WAD” - Microcontroller Integrates Sensors and Timers for Water, Agitation and Drainage

Question 3(c OR) [7 marks]

#

Draw and explain block diagram of Microwave oven. List wiring and safety instructions for microwave oven

Answer:

Microwave Oven Block Diagram:

flowchart LR
    A[Control Panel] --> B[Control Circuit]
    B --> C[High Voltage Transformer]
    C --> D[High Voltage Capacitor]
    D --> E[Magnetron]
    E --> F[Waveguide]
    F --> G[Cooking Cavity]
    B --> H[Turntable Motor]
    B --> I[Fan Motor]
    B --> J[Door Interlock Switches]

• Control Circuit: Processes user inputs and controls timing
• High Voltage Transformer: Steps up voltage to 2000-4000V
• Magnetron: Generates microwave radiation at 2.45 GHz
• Waveguide: Directs microwaves into cooking cavity
• Turntable: Ensures even cooking through rotation

Safety Instructions:

• Never operate with door open or damaged
• Ensure proper grounding
• Don’t override safety interlocks
• Use microwave-safe containers only

Wiring Instructions:

• Use appropriate gauge power cable (typically 14-16 AWG)
• Connect to dedicated 15-20A circuit
• Ensure proper ground connection
• Keep wiring away from heat sources

Mnemonic: “MAGIC” - Magnetron And Guided waves Into Cavity

Question 4(a) [3 marks]

#

Draw block diagram of Photocopier.

Answer:

Photocopier Block Diagram:

flowchart TD
    A[Document Scanner] --> B[Image Processor]
    B --> C[Laser Unit]
    C --> D[Photosensitive Drum]
    E[Charging Unit] --> D
    D --> F[Developer Unit]
    F --> G[Transfer Unit]
    G --> H[Paper Feed]
    G --> I[Fusing Unit]
    I --> J[Output Tray]

• Scanner: Captures original document image
• Drum: Holds electrostatic image
• Developer: Applies toner to charged areas
• Transfer: Transfers toner to paper
• Fuser: Melts toner permanently onto paper

Mnemonic: “SDTFO” - Scan, Develop, Transfer, Fuse, Output

Question 4(b) [4 marks]

#

List specifications of MF printer and CCTV.

Answer:

Specifications:

Mnemonic: “RSCPF” - Resolution, Speed, Capacity, Protocol, Function specifications

Question 4(c) [7 marks]

#

Explain working of laser printer with block diagram.

Answer:

Laser Printer Working:

flowchart TD
    A[Data Processing] --> B[Laser Unit]
    B --> C[Photosensitive Drum]
    D[Primary Corona] --> C
    C --> E[Developer Unit]
    E --> F[Transfer Corona]
    F --> G[Paper Transport]
    G --> H[Fusing Unit]
    H --> I[Output]
    J[Cleaning Unit] --> C

Working Process:

1. Charging: Corona wire gives drum uniform negative charge
2. Writing: Laser neutralizes charges on drum to form image
3. Developing: Toner adheres to discharged areas of drum
4. Transfer: Paper receives positive charge, attracts toner
5. Fusing: Heat and pressure melt toner onto paper
6. Cleaning: Residual toner is removed from drum

• Resolution: Determined by laser precision (600-1200 dpi)
• Speed: Based on drum rotation and paper transport (15-40 ppm)

Mnemonic: “CWTFC” - Charge, Write, Transfer, Fuse, Clean cycle

Question 4(a OR) [3 marks]

#

Draw block diagram of CCTV.

Answer:

CCTV System Block Diagram:

flowchart LR
    A[Cameras] --> B[Video Transmission]
    B --> C[Digital Video Recorder]
    C --> D[Storage HDD]
    C --> E[Monitor Display]
    F[Power Supply] --> A
    F --> C
    G[Network Switch] --> C
    C --> H[Remote Access]

• Cameras: Capture video footage
• Transmission: Coaxial cable/IP network/Wireless
• DVR/NVR: Processes and records video
• Storage: Hard drives for footage retention
• Monitor: Displays live or recorded footage

Mnemonic: “CTDSM” - Camera, Transmission, DVR, Storage, Monitor system

Question 4(b OR) [4 marks]

#

List specifications of inkjet printer and Photocopier.

Answer:

Specifications:

Mnemonic: “RSIPCD” - Resolution, Speed, Ink/toner, Paper capacity, Connectivity, Duty cycle

Question 4(c OR) [7 marks]

#

Explain working of LCD projector with block diagram and list its specifications.

Answer:

LCD Projector Working:

flowchart LR
    A[Input Source] --> B[Signal Processor]
    B --> C[Lamp/Light Source]
    C --> D[Condenser Lens]
    D --> E[Dichroic Mirrors]
    E -->|Red| F[Red LCD Panel]
    E -->|Green| G[Green LCD Panel]
    E -->|Blue| H[Blue LCD Panel]
    F --> I[Prism]
    G --> I
    H --> I
    I --> J[Projection Lens]
    J --> K[Screen]

Working Process:

1. Light Generation: High-intensity lamp produces white light
2. Color Separation: Dichroic mirrors split light into RGB
3. Modulation: LCD panels control light intensity for each color
4. Recombination: Prism reassembles RGB images
5. Projection: Lens system projects image onto screen

Specifications:

• Resolution: XGA (1024×768), WXGA (1280×800), FHD (1920×1080)
• Brightness: 2000-5000 ANSI lumens
• Contrast Ratio: 2000:1 to 20000:1
• Lamp Life: 3000-6000 hours
• Throw Ratio: 0.5:1 to 2.0:1
• Connectivity: HDMI, VGA, USB, Wi-Fi

Mnemonic: “LSPMPS” - Lamp, Split, Panels, Modulate, Prism, Screen

Question 5(a) [3 marks]

#

Draw block diagram of PA system.

Answer:

Public Address (PA) System Block Diagram:

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

• Microphone: Converts sound to electrical signals
• Pre-amplifier: Boosts microphone signal
• Mixer: Combines multiple audio sources
• Equalizer: Adjusts frequency response
• Power Amplifier: Increases signal power
• Speakers: Convert electrical signals back to sound

Mnemonic: “MMEPS” - Microphone, Mixer, Equalizer, Power amp, Speakers

Question 5(b) [4 marks]

#

Explain tweeter and woofer.

Answer:

Speaker Components:

Working Principle:

flowchart TD
    A[Audio Signal] --> B[Crossover Network]
    B -->|High Frequencies| C[Tweeter]
    B -->|Low Frequencies| D[Woofer]
    C --> E[High-Frequency Sound Waves]
    D --> F[Low-Frequency Sound Waves]

• Tweeter: Reproduces high frequencies with clarity and detail
• Woofer: Reproduces low frequencies with power and depth

Mnemonic: “THSL” - Tweeters handle Highs, Small and Light; Woofers handle Lows

Question 5(c) [7 marks]

#

Define microphone. List types of microphone and explain working of any one type of microphone.

Answer:

Microphone Definition: A microphone is an electroacoustic transducer that converts sound waves into electrical signals.

Types of Microphones:

Dynamic Microphone Working:

flowchart TD
    A[Sound Waves] --> B[Diaphragm]
    B --> C[Attached Coil]
    C --> D[Movement in Magnetic Field]
    D --> E[Induced Voltage]
    E --> F[Electrical Signal Output]

• Sound Capture: Diaphragm vibrates with sound waves
• Transduction: Coil attached to diaphragm moves within magnetic field
• Signal Generation: Movement induces voltage proportional to sound intensity
• Output: Low impedance, strong signal requiring minimal amplification
• Advantages: Durable, handles high SPL, no external power needed

Mnemonic: “DDCMIO” - Diaphragm Displaces Coil in Magnetic field Inducing Output

Question 5(a OR) [3 marks]

#

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

Answer:

Definitions:

Diagram:

Mnemonic: “PLR Sound” - Pitch defines tone, Loudspeaker produces it, Reverberation extends it

Question 5(b OR) [4 marks]

#

Draw block diagram of Home theatre sound system and explain in brief.

Answer:

Home Theatre Sound System:

flowchart TD
    A[Audio/Video Source] --> B[AV Receiver/Amplifier]
    B --> C[Front Speakers]
    B --> D[Center Speaker]
    B --> E[Surround Speakers]
    B --> F[Subwoofer]
    B --> G[Video Display]
    H[Remote Control] --> B

• AV Receiver: Central hub that processes audio/video signals
• Front Speakers: Left and right channels for stereo sound
• Center Speaker: Delivers dialog and central sounds
• Surround Speakers: Create immersive environment with ambient sounds
• Subwoofer: Reproduces low-frequency effects (LFE) below 120Hz
• Configuration: Common setups include 2.1, 5.1, 7.1, or 9.1 channel systems

Mnemonic: “AFSCS” - Amplifier drives Front, Surround, Center Speakers and Subwoofer

Question 5(c OR) [7 marks]

#

Explain Electrostatic loudspeaker and permanent magnet loudspeaker.

Answer:

Comparison of Loudspeaker Types:

Electrostatic Speaker Working:

flowchart LR
    A[Audio Signal] --> B[Step-up Transformer]
    C[High Voltage DC Supply] --> D[Charged Diaphragm]
    B --> E[Conductive Stator Plates]
    E --> F[Electrostatic Force]
    F --> D
    D --> G[Sound Waves]

• Diaphragm: Thin, lightweight membrane with conductive coating
• Operation: Audio signal varies charge on stator plates, creating varying force on diaphragm

Permanent Magnet Speaker Working:

flowchart LR
    A[Audio Signal] --> B[Voice Coil]
    C[Permanent Magnet] --> D[Magnetic Field]
    B --> E[Current in Coil]
    E[Current in Coil] --> F[Electromagnetic Force]
    F --> G[Cone Displacement]
    G --> H[Air Movement]
    H --> I[Sound Waves]

• Voice Coil: Winding of wire attached to speaker cone
• Operation: Current through coil creates magnetic field that interacts with permanent magnet
• Advantages: Robust design, good power handling, no high voltage required
• Applications: Most common speaker design for general audio reproduction

Mnemonic: “ESPM” - Electrostatic uses Static charges, Permanent Magnet uses Magnetic forces