Deck 41: Systems Troubleshooting

Question 1

In Fig. 41-18, a +5-V signal is applied to the input of the transistor. The LED does not light. A measurement at the collector of the transistor reveals a voltage of +5 V. What are the most likely problems

Answer 1

The proper circuit operation is that when the input of the transistor is +5 V the transistor conducts and the LED glows. When the input of the transistor is low then the transistor is opened and the LED doesn't glow.
Even when the input of the transistor is +5 V and if the LED doesn't glow then the possible errors are
• The transistor failed.
• The resistor must be opened.
• The resistor must be opened.
• The LED failed.

Question 2

The most common job of an electronics technician is

A) design.
B) circuit analysis.
C) testing.
D) troubleshooting.

Answer 2

Troubleshooting is a science and art of finding the errors or failures in the circuits, equipment and electronic systems. It relies mostly on basic knowledge on the equipment and components.
Design, circuit analysis and testing need more technical knowledge, whereas the troubleshooting requires basic knowledge on the equipment. Hence, most common job for a technician is troubleshooting.
Thus, the correct option is .

Question 3

In Fig. 41-19, the circuit is not performing as it should. This schematic is all you have. Determine what the output is supposed to be. Measuring the output, you get a dc voltage value of -12 V. What is the problem

Answer 3

Consider the circuit in the Figure 41-19,
• The output of the op-amp is • The output of the op-amp is since it is a positive unit gain amplifier.
• The output of the op-amp is • The resistors are in parallel and forms a .
• The input to the resistor formed is • Total output is Hence the output that is supposed to be is It is given that the output measured was the problems can be as follows
• The op-amps are malfunctioned.
• The feedback resistors may offer more resistance.
• The input resistors may offer less resistance.

Question 4

Which test instrument presents its output in the frequency domain

A) Spectrum analyzer.
B) Oscilloscope.
C) Multimeter.
D) Logic analyzer.

Question 5

Consider the circuit of Fig. 41-20. What is the desired output If the output is a series of 60-Hzpulses across D 2 , what is the most likely problem

Question 6

Which test instrument presents its output in the time domain

A) Spectrum analyzer.
B) Oscilloscope.
C) Multimeter.
D) Signal generator.

Question 7

In Fig. 41-21, the circuits are operating properly except for a 500-kHz signal riding on the 8-V dc output. What may be the problem

Question 8

The spectrum analyzer shows what characteristic on the vertical scale of the output

A) Voltage.
B) Current.
C) Power.
D) Impedance.

Question 9

One of the PC board modules in a piece of equipment has failed. A replacement board costs $85. There pair can be made by just plugging in a new board. On the other hand, a technician can repair the board in an estimated 2 hours if the $6 defective IC is available. The technician cost is $45 per hour. What is the recommended solution

Question 10

A signal generator that produces sine, square, and triangular waves from about 1 Hz to 6 MHz is called a(n)

A) RF signal generator.
B) AWG.
C) function generator.
D) frequency synthesizer.

Question 11

If documentation is not available for the device or system you are troubleshooting, what may be a way to get that

Question 12

Most modern test instruments are

A) analog.
B) digital.

Question 13

In the garage door example given in Fig. 41-14, the door will open but not close. What may be the problem

Question 14

What is the first process that an input signal encounters in a modern test instrument

A) Filtering.
B) Frequency conversion.
C) Digital-to-analog conversion.
D) Analog-to-digital conversion.

Question 15

In the home entertainment center of Fig. 41-17,the TV set is working but you cannot play a movie DVD. Give several reasons why you cannot do this.

Question 16

In a modern test instrument, how is the measurement actually made

A) An embedded microcontroller processes the digital input.
B) Analog circuits interpret the signal and display it.
C) The signal is directly displayed for the user to measure.
D) Level comparators decide the signal amplitude.

Question 17

The automatic lawn sprinkler system, shown in Fig. 41-22, has four zones of operation. Water sprinkler heads in each zone turn on in sequence for a specific amount of time.

Question 18

A virtual instrument generally uses what to process the input signal

A) Embedded controller.
B) Personal or laptop computer.
C) An FPGA or DSP chip.
D) No processing is done.

Question 19

What makes the measurement in a virtual instrument

A) Hardware.
B) Software.

Question 20

What is the name of the software that is used to create virtual instruments

A) The C language.
B) Java.
C) LabVIEW.
D) MathCAD.

Question 21

Which of the following is not part of an AWG

A) DAC.
B) Frequency synthesizer.
C) Memory.
D) ADC.

Question 22

It is often more economical and faster to replace a product or subassembly than to repair it.

Question 23

The first step in most troubleshooting processes is to

A) isolate the problem.
B) do a visual inspection.
C) verify that the problem exists.
D) check for power.

Question 24

You should not attempt to troubleshoot a piece of equipment without

A) the documentation.
B) an oscilloscope.
C) multimeter.
D) training.

Question 25

Electronic components are generally more likely to fail than mechanical components.

Question 26

A good first step in troubleshooting a circuit is to

A) test all transistors.
B) check for overheated ICs.
C) verify that the correct dc voltages are present.
D) begin signal tracing.

Question 27

In Fig. 41-8, the input to stage 1 is good and the output from stage 4 is not correct. The problem lies in

A) stage 1.
B) stage 2.
C) stage 4.
D) any of the stages.

Question 28

In Fig. 41-8, there is no output from stage 1. The problem is

A) a defective stage 1.
B) no input signal.
C) either a or b.
D) not having enough information to determine.

Question 29

Most detailed troubleshooting should not begin unless

A) you have the documentation.
B) you are familiar with the equipment.
C) you have been trained on the equipment.
D) all of the above.

Question 30

The most likely component to fail in a system is a(n)

A) diode.
B) integrated circuit.
C) capacitor.
D) resistor.

Question 31

Which is often the primary goal of troubleshooting a piece of equipment

A) Low cost.
B) Minimum downtime.
C) Continued long product life.
D) No need for experienced repairers.

Question 32

For complex digital circuit troubleshooting, the best instrument is probably the

A) oscilloscope.
B) spectrum analyzer.
C) logic analyzer.
D) signal generator.

Question 33

In systems troubleshooting, it is best to approach the problem with

A) block diagram analysis.
B) schematic diagram analysis.
C) testing all individual components.
D) replacement of complete subsystems.

Question 34

A quick but expensive and often effective troubleshooting approach is

A) complete unit replacement.
B) component or module substitution.
C) signal tracing to the component level.
D) dc voltage measurement.