Fault Finding and Reliability

• When a fault occurs, the person fixing it must consider the fault and related problems.

The Nine Point Plan for Fault Finding

• Determine what the problem is.
• Define the objective.
• Identify possible causes.
• Gather the facts.
• Determine the actual cause/problem.
• Identify possible steps to take.
• Decide on the best action to take.
• Take action.
• Archive the results.

Preventative Maintenance

• Service to check a machine's components' working condition.

Uptime

• Maximum use of equipment or system, working according to plan.

Downtime

• When system failure occurs and repairs are needed.

Factors Affecting Reliability

• Power dissipation.
• Mechanical stress.
• Environmental conditions.
• Temperature variations.
• Shock or vibration.
• Pressure radiation.

Methods for Collecting Facts (Nine Point Rule)

• Examine records.
• Determine applicable rules.
• Communicate with involved people.

Factors Influencing Decisions ("What are the Facts?")

• Situation factor: What happened and how.
• Human factor: Who was involved and influences the fault identification.
• Place factor: How the location impacts what happened.
• Time factor: When the fault occurred and its importance.
• Casual factor: Why the fault happened and if it's a recurring issue.

Aids for Fault Finding Documentation

• Functional block diagrams.
• Test data charts.
• Layout diagrams.
• Test flowcharts.
• Symptom analysis charts.

Ten Basic Rules of Fault Finding

• Understand basic component operation.
• Learn typical circuits.
• Know how to use equipment.
• Redraw complex circuits.
• Use a logical, systematic process to eliminate possible faults.
• Facts must be tested.
• Record results.
• Avoid indiscriminate adjustments.
• Test after completing repairs for proper operation.

Uses of a Simple Inching Circuit

• Accurate hoisting/lowering.
• Setting up machines.
• Positioning of work pieces.

Types of Polarized Capacitors

• Electrolytic capacitors.
• Tantalum capacitors.

Types of Non-Polarized Capacitors

• Ceramic.
• Paper dielectric.
• Silver-mica.
• Polystyrene.
• Polyester film.
• Paloycarbonate.

Two Types of Overload Protection

• Electromagnetic overload.
• Thermal overload.

Purpose of a Diode in AC Circuits

• Blocks DC circuits.
• Used as a rectifier.

Methods Used in Systematic Fault Finding

• Basic approach.
• Scientific approach.
• Half-cut method.
• Systematic approach.

Difference Between Ammeters and Voltmeters

• Ammeters have low resistance; voltmeters have high resistance.

Difference Between Capacitors and Inductors

• A capacitor stores electrical charge.
• An inductor produces a magnetic field.

Advantages of a Metal Oxide Resistor

• High stability.
• High power rating.
• High-temperature stability.
• Low noise level.
• Low production cost.
• Heat resistor accuracy.

Types of Core Losses

• Eddy current.
• Hysteresis.
• Iron core.
• Copper.

Deflection Plates of an Oscilloscope

• Plates inside that deflect the electron beam.

Purpose of a Luminous Spot

• Converts accelerated electrons into light to appear on the screen.

Disadvantage of a Moving-Coil Meter

• Measures only direct currents.

Functions of Dielectric Materials

• Supports electrical components.
• Used as a dielectric capacitor.

Factors That Influence Dielectric Properties

• Temperature.
• Moisture.
• Frequency.
• Field strength.

Decoupling Capacitor in a Transistor Circuit

• Shorts circuit spikes.
• Shorts AC voltage on the emitter to ground.

Three Types of Basic Amplifier Circuits

• Common collector: Current amplification.
• Common base: Voltage amplification.
• Common emitter: Current or Voltage amplification.

Holding Current in SCR

• Minimum current to keep an SCR in conduction.

Force Commutation

• Switching off an SCR to stop conduction.

Types of Moving Iron Instruments

• Attraction type.
• Repulsion type.

Three Operating Areas of a Transistor

• Cut-off region.
• Active region.
• Saturation region.

Three Methods to Cause an SCR to Conduct

• Positive gate current.
• Anode positive voltage.
• Transient on the gate.

De Morgan's First Theorem

• The AND of inverted inputs is equivalent to the OR function of inverted inputs.

De Morgan's Second Theorem

• The OR of inverted inputs is equivalent to the AND function of the inverted inputs.