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Self Test


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200.1 What is the best way to verify an indication given by an item of test equipment?
Compare it with a known good item of test equipment, such as a shop standard
200.2 What internal device does some test equipment use to eliminate moisture
Built in heaters
200.3 What should be done to test equipment when it is not in use?
Store in a dry place, cover with dust covers, and/or store in its case
201.2 Why must we unsolder one side of a resistor before making a resistance measurement?
To prevent erroneous readings on the ohmmeter
201.3 List two precautions you should take before making a resistance measurement
1. Remove power from the circuit under test
2. Disconnect any meters or other devices that may be damaged by current from the ohmmeter
201.4 What test set is used to check a transmitters frequency?
A frequency counter or spectrum analyzer
202.1 List at least three troubleshooting aides
Fault indicators; built in test equipment; flow charts; chechout and alignment procedures; and specialized test equipment.
202.2 What is the most important step of any troubleshooting effort?
Think before you act
203.1 List the steps of general troubleshooting procedures used to locate the trouble.
1. Recognize failure
2. Isolate to defective area
3. Isolate to a defective unit
4. Isolate the defective circuit card or module
5. Replace or repair the defective part
6. Test the circuits operation
203.2 Which steps can you sometimes eliminate?
Steps 2, 3, and 4
203.3 Which steps must you always follow?
Steps 5 and 6
204.1 What are the two main categories of equipment inspections?
Regular visual inspections and functional inspections you do through periodic tests
204.2 When do you do bench checks
Only when you have determined that some sort of failure or possibility of failure exists in the suspect equipment
204.3 What does comparison of periodic maintenance inspection data reveal?
It reveals slow, progressive drifts that may be too small to show up significantly in any one test
205.1 How can you determine if a distan-end system failure is creating the problem?
Perform a system in-house loopback
205.2 What is the quickest way to return a system to full operation?
Unit substitution
205.3 What are diagnostic test for?
To isolate the defective card or module
206.1 What type tests would be performed in this step?
Resistance measurements, voltage measurements, and waveform comparison
206.2 What step should be done before making a resistance measurement?
Make sure all power to equipment under test is off and discharge all filter capacitors
206.3 What is the advantage of voltage measurements compared to other measurements?
Circuit operation is not interrupted
206.4 When taking voltage measurements, what should you do to prevent damaging the voltmeter?
Set the voltmeter on the highest range initially so that any excessive voltages do not overload the meter
206.5 Name two unusual conditions that could cause low voltages to be hazardous.
Any two of these; excessive humidity, wet areas, lack of protective matting or other equipment, and
206.6 What steps should you follow when measuring voltages over 600 V?
1. shut off the circuit power, discharge any filter capacitors, and temporarily ground the point
2. Connect the proper test lead to the high potential point and move away from the voltmeter. Do not come in contact with any part of the equipment while the power is on
206.7 If you suspect that an incoming waveform does not meet specifications, which technique and type of test equipment would you use?
Use an oscilloscope and compare waveforms to the specifications listed in the applicable technical order
207.1 How many cards are you allowed to replace at any one time when using the group removal and replacement method?
1/2 of the circuit cards, not to exceed seven
207.2 What is the advantage of using the group removal and replacement technique?
It provides for quick restoration of equipment
207.4 What was the method of troubleshooting used in the text to diagnose the equipment malfunction?
Half split
207.5 What is an operational check?
It test a unit that previously malfunctioned
207.6 What is a system check?
It ensures all circuits are operating and serving their designed purpose
208.1 Explain the purpose of the meters range switch.
The range switch is used to obtain any of the meter's ranges or functions
208.2 List the ranges for AC/DC voltage measurements.
2.5V, 10V, 50V, 250V, 1,000V, AND 5000V
208.3 List the three ranges for restistance measurements.
R*1, R*100, R*10,000
208.4 Where do you set the function switch for measuring resistance?
-DC or +DC
208.5 How do you calibrate the meter pointer for zero ohms when you measure resistance?
Short the test leads together and adjust the zero ohms control to move the pointer to zero ohms
208.6 Which control compensates for the meter's internal batteries?
Zero ohms control
208.7 Which circuit jacks get the most usage?
The common(-) and (+) jacks
208.8 When might you have to use the reset button?
When an overload (voltage or current) triggers the protection circuit, the reset button "clicks" or "pops up". Pressing down and releasing the reset button should return the meter to normal operation
209.1 When preparing to measure resistance, what is the first thing you must do before you make a measurement?
Be sure that no power is applied to the circuit and that all capacitors are discharged
209.2 How often do you "zero" an analog multimeter during resistance measurements?
"zero" the meter each time you select a new range
209.3 How can you electrically isolate a resistor from its circuit when measuring resistance?
You can electrically isolate a component by disconnecting one of the resistors soldered connections
209.4 On what part of the meter's scale can you best read resistance measurements?
Mid-to right-scale
209.5 What is the difference between measuring DC voltage and AC voltage with regard to the test leads?
The polarity of the test leads is not important when measuring AC voltages
209.6 How do you place the test leads when measuring voltage?
Place the test leads in parallel to measure voltage
209.7 How do you place the test leads to measure current?
Place the test leads in series to measure current
210.1 Which control do you use to select the meter's different measurement functions?
The rotary switch
210.2 List the four types of information presented in the multimeter's display?
(1) Digital display, (2) visual annunciators, (3) analog bar graph, and(4)range indicator
210.3 Which information in the display section shows the absolute value of the input?
Analog Bar Graph
210.4 Describe the function of the range push button.
The range push button lets you manually select the measurement range
210.5 What is the purpose of the touch-hold push button?
The touch-hold push button locks the measurement into the display for viewing and automatically updates the display when you take a new measurement
210.6 List the multimeters four input jacks.
(1) amperes, (2) milliamps/microamps, (3) volts/ohms/diode, and (4) common
210.7 When does the 8025A perform a power-up self test?
When you move the rotary switch to any position from the OFF position
211.1 What two ranges of DC voltages can you measure using the 8025A multimeter?
-1,000 to +1,000 volts DC; -320 to +320 millivolts DC
211.2 What is the maximum amount of continuous AC current that you can measure with the multimeter?
10 amps
211.3 When using the Fluke 8025A, how do you know you're in the resistance measurement function?
The ohms annunciator is showing in the display
211.4 How do you determine if you're testing a "good" diode with the 8025A?
Placing the leads across a "good" diode produces "OL" in the display while reversing the leads produces a continuous audible tone.
212.1 What type of display does the oscilloscope present?
Amplitude VS time
212.2 On which axis of an oscilloscope is votage, time, and depth information presented?
Voltage=vertical axis, time = horizontal axis, and depth =intensity
212.3 What is the purpose of teh delay line at the input of the vertical amplifier?
It allows the sweep generator circuitry time to start a sweep before the signal reaches the cathode ray tube vertical deflection plates. This enables you to view the leading edge of the signal waveform.
212.4 What position of the input coupling switch is used to view digital type or square wave signals?
DC coupling
213.1 What is teh purpose of the trigger circuit?
To produce a stable display
213.2 In the normal mode, is a trigger signal required?
213.3 What is the purpose of teh trigger level and slope control?
It permits you to select any point on the positive or negative edge of the displayed waveform to trigger the sweep circuit.
213.4 If one was tracking a problem related to the AC power (power line hum), what type of triggering would be used?
Line triggering
213.5 What is the next step after centering the trace?
Adjust the intensity control for comfortable viewing; then adjust the focus for the sharpest trace
213.6 Is the VOLTS/CM control adjusted for its lowest or highest setting?
Highest to prevent the trace from being deflected off the screen if the signal has a large DC component or is a very large AC signal.
213.7 What setting of the input coupling switch should be used to view a low fequency digital signal?
213.8 Why should your scope's input filter be used?
To keep the trigger signal clean and noise free
213.9 How would you set up your triggering controls if the input trigger signal has a large DC component?
Use the AC position of your trigger input controls.
214.1 What is the basic purpose of the oscilloscope probe?
To provide isolation for scope inputs and prevent circuit loading.
214.2 List four types of probes
The high resistance, passive divider and times 1 probes, active (field effect transistor), and current probes.
214.3 What is the typical input impedance of most oscilloscopes?
One megohm shunted by 20pF capacitance
214.4 When making an amplitude measurement and the source impedance is unknown, greatest accuracy is achieved when the probe's Z is what?
215.1 What is the first thing to check before using a divider probe for accurate measurments (assume the scope is already set up)?
Probe compensation
215.2 When is it necessary to check for probe compensation?
At the beginning of each work day, whenever you reconnect a probe to a different input connector, and when you change probes
215.3 How is rise time measured on a pulse waveform?
Measured between the 10 and 90 percent amplitude points on the leading edge of the pulse
215.4 Where is pulse width measured on a pulse waveform?
At the 50 percent amplitude points
215.5 If the TIME/DIV dial is set at .2 microseconds, and the width of the pulse is measured as 3 divisions on the scope graticule, what is the pulse width?
1.6 microseconds
215.6 Calculate the frequency of a signal in which one cycle covers 4 horizontal divisions. The TIME/DIV dial is set at 1 microsecond.
250 khz
216.1 How can X - Y operation in a third dimension?
by modulating the beam's intensity through the Z axis
216.2 What is the Lissajorous pattern for each of the following relationships?
a) Two signals exactly in phase with each other
b) Two signals with the same frequency but 30 degrees out of phase
c) two signals with the same frequency, but 9
(a) A line leaning at a 45 degree angle, (b) an oblong circle leaning at an angle, (c) A perfect circle, (d) a pattern with horizontal tangent points (bumps) and vertical tangent points (bumps); the ratio of the number of tangent points is equal to the ratio of the two frequencies
216.3 In the X-Y operation, if the vertical input frequency is 1 kHz, what is the horizontal frequency with a frequency ratio of 2:1?
2 kHz
216.4 How can an oscilloscope be set up to act as a simple network analyzer?
connect a sweep signal generator to the input of the circuit under test, and the sweep voltage to the X axis input of the o'scope. Then the output of the circuit under test is connected to the o'scopes Y axis (vertical input)
217.1 What is the biggest difference between digital storage oscilloscopes and analog scopes?
Digital storage oscilloscopes digitize the input signal for storage or display
217.2 What is the function of charged coupled devices in the digital storage oscilloscope's signal sampling process?
Charged coupled devices accept fas changing data and send it to the analog to digital converter at a slower rate for more accurate data collection
217.3 Define the following waveform storage terms:
waveform points
waveform record
record length
a. Sampled data points stored in the digital storage oscilloscopes memory
b. Stored waveform points
c. number of waveform points used to make up a record
217.3 Define the following waveform storage terms:
a. waveform points
b. waveform records
c. Record length
a. Sampled data points stored in the digital storage oscilloscopes memory
b. Stored waveform points that make up the waveform record
c. Number of waveform points used to make the waveform record
217.4 What advantage does retrieving data from memory have on the cathode ray tube?
It allows the cathode ray tube to receive data at a slower rate as opposed to keeping up with some of the high frequency signals fired directly on a cathode ray tube in an analog scope.
217.5 List two digital storage oscilloscope sampling techniques.
Real time and repetitive sampling
217.6 Define Interpolation
This is a process that estimates what the signal will look like between samples and "fill in the blanks" between data points.
217.7 What are the two types of Interpolation?
Linear and sine
217.8 What is the difference between sequential and random sampling?
Sequential sampling takes a sample at a predetermined time after the trigger in a progressive order until there are enough data points to reconstruct several periods of the signal. Random sampling takes samples at an undetermined point on a signal and stores them.
217.9 What is a common cause of aliasing?
Undersampling due to having the time base turned down too low, thus reducing the sample rate for a frequency that is too high for a given setting.
217.10 Describe the three times of acquisition modes.
1. In sample mode, the digital storage oscilloscope creates a record point by saving the first sample in a collection of sample points
2. In peak detect mode, the digital storage oscilloscope saves the highest and lowest points in a collections of samples
3. In averaging mode, the digital storage oscilloscope shows a record that is a collection of several acquisitions of a repeated signal that is averaged over time.
217.11 What is the function of the acquisition controls?
To set the digital storage oscilloscope's sampling rate, determine what type of processing will occur and how many record points can be shown.
217.12 What is the range of record points that the Textronix 2230 digital storage oscilloscope can acquire?
1000 to 4000 points
217.13 Which control sets up acquisition either before a trigger or at the beginning of a waveform?
217.14 What happens to the NORM and P-P AUTO trigger modes while in ROLL mode?
These triggers are disabled allowing the digital storage oscilloscope to continuously acquire and display incoming signals.
217.15 In the norm trigger mode, how are the pretrigger waveform and post trigger scan updated?
The pretrigger waveform is updated by the trigger and post trigger scan from the trigger position to the right
217.16 In the SAVE mode, what happens to the acquisition and display update in progress?
It stops
217.17 What types of measurements in the STORE mode are made with CURSORS controls?
Delta volts, delta time, one over delta time, and delay time measurents.
217.18 Which switch establishes the function of the CURSORS position control?
217.19 Explain how a 4K record length is shown on the display?
A 4-bar graph on the screen indicates which portion of the record you are viewing. A 4K record length displays 1K samples at a time. You have to look at four differen screens to see the entire record length
217.20 In the SELECT WAVEFORM mode using the SELECT C1/C2 (cursor select) switch, what happens when the C1/C2 switch is pressed?
It moves the cursor set between displayed waveforms
217.21 What is the purpose of the MEMORY and menu controls?
They control the MENU operation while the MENU is displayed, and they control the storage and display of the SAVE reference waveforms when the MENU is not displayed.
218.1 What is the purpose of the bit error rate test set?
To provide a bit error detection system that can determine the received data quality
218.2 What type of test can the bit error rate test set perform?
Bit error analysis, timing analysis, or delay measurements. Also, the bit error rate test set is a source of pulse code modulsation(PCM) data used to test a communications data link or bit synchronizer output. Many bit error rate test set can generate command test patterns, telemetry PCM formats, and bit coding patterns at telemetry data rates.
218.3 What is the purpose of the internal clock generator?
To provide an internal clock reference usually selectable from the front panel
218.4 What is the purpose of the voltage controlled oscillator, and how is it calibrated?
As the basic clock generator, it provides all clock phases. It is periodically frequency calibrated by a crystal controlled oscillator in the AUTO-CAL section.
218.5 What is the purpose of the countdown section of the internal clock generator?
To divide the voltage controlled oscillator clock and provide a frequency equal to the bit rate selected.
218.6 What is the purpose of the digital to analog converter and the decode range splitter, and for what purpose does this section use the binary coded decimal information?
To use binary coded decimal information to control the voltage controlled oscillator center frequency, and to control the range the countdown circuits will decode. They use the binary coded decimal information to control the voltage controlled oscillator center frequency, and to control the range the countdown circuits will decode.
218.7 What is the purpose of the pattern simulator?
To accept either the external or internal clock and generate either a pseudo random noise pattern or a 48 bit pattern you program from the front panel
218.8 Which pattern simulator section controls the clock selector and selects either the external clock or the internal clock for processing?
Data/clock select encoder
218.9 What is the purpose of the pseudo random noise generator?
To receive the internal clock from the clock selector and generate a 2,047 bit long pseudo random pattern
218.10 What is the purpose of the pseudo ranom noise blanking generator, and what are the blanking periods?
To provide a blanking period at the start of the 2,047 bit pseudo random noise fram (under the control of the blanking selector switch). The blanking period can be 0, 32, 64, 96, or 128 bits long.
218.11 What is the purpose of the 48 bit register and 8 bit word display?
To accept six 8 bit words, one word at a time, from the data entry switches and store them in a 48 bit register
218.12 What controls the data/clock select encoder, and what does it generate?
The pattern slect and clock select switches; it generates a data select code and a clock select code
218.13 Which pattern simulator section selects either pseudo random noise data, external data, or 48 bit data depending on which data select code is received?
Data/sync selector
218.14 What is the purpose of the code converter?
To convert the non return zero level (nrz-l) data into the desired coding, such as NRZ-mark (NRZ-M)
218.15 What is the purpose of the clock drivers and the data drivers, and where are their outputs sent?
The clock drivers convert the selected clock signal to a system compatible level and a buffered transistor transistor logic (TTL) level, and the data drivers convert the encoded data signal to a system compatible level and buffered TTL level. The outputs are input to the pattern synchronizer and error counter data/clock receivers block
218.16 What is the output from the output amplifier?
After mixing the three input signals linearly, it prvides a front panel adjustable offset and output level for a low impedance load
218.17 What is the purpose of the pattern synchronizer and error counter?
To recieve the selected pattern, automatically synchronizes on the pattern, and determine the bit error rate induced after transission through the system.
218.18 What are the inputs to the data/clock receivers?
Either system compatible data or buffered TTL data from the clock drivers and the data
218.19 Which pattern synchronizer and error counter sections combine (OR) the system compatible and TTL signals together so only one signal will be present at one time?
Data/clock receivers
218.20 To what sections are the outputs from the data/clock receivers sent?
To the 48 bit synchronizer/comparator, the pseudo random noise synchronzer/comparator, the external data synchronizer/comparitor, and the error rate counter and display sections
218.21 What is the purpose of the 48 bit synchronizer/comparator?
To accept the received clock and data, and synchronize on the pattern when it's equal to the 48 bit parallel input
218.22 What is the purpose of the pseudo random noise pattern synchronizer/comparator
To accept the received clock and data, from the data/clock receivers, and will synchronize with the pattern when it's equal to its own 2,047 bit pseudo random noise pattern
218.23 What is the purpse of the external data pattern syncronizer/comparator?
To accept the external data, delay it under the front panel control, and compare it with the received data from the data/clock receivers
218.24 Where does the error/IN SYNC selector send the correct error and IN SYNC signal?
To the error rate counter and display
218.25 When will the pattern synchronizer and error counter err/IN SYNC section provide an output to the front panel display, and what will interrupt this output?
At the end of the count cycle or when you push the reset switch. A reset pulse will interrupt this output.
219.1 What is the primary means of measuring the quality of transmitted digital information?
To compare the number of bits in error to the total number of bits transmitted. The ratio of the number of bits in error to total number of bits transmitted
219.2 What is the basic quality measurement for a transmission channel?
The bit error rate
219.3 What is the difference between random distribution of error and an error rate with a clustered distribution?
In a random distribution, each bit is equally likely to be in error. In a cluster distribution, the errors occur in clusters
219.4 What are the steps in the basic bit error rate testing procedure?
1. A known bit pattern usually pseudo random, is generated at the sending end of the data channel or equipment under test, and is transmitted through the channel.
2. At the receiving end, an identical pattern is generated and synchronized with the incoming signal
3. The received signal is compared to the locally generated pattern in the receiving equipment
4. If any bit in the received signal is not the same as the generated bit, it is assumed to received bit is in error.
5. An error signal is generated and used to operate a counter.
219.5 Although bit error rate test sets use the same basic technique to count errors, how do you interpret the results and display information?
In many differen ways. So, you must use and understand the technical manual for the particular test equipment.
219.6 What are some significant bit error rate test equipment parameters?
1. Bit rate and timing
2. Test patterns
3. Synchronization
4. Interface and data coding
5. Readouts and special features
219.7 How can the bit error rate test set, with internal timing for a low or intermediate bit rate range, be used to operate at higher bit rates?
With external timing
219.8 What data circuit speed would normally use the shorter generated bit error rate test pattern lengths, and what is the data circuit bit rate?
Low to intermediate; 1200 to 9600
219.9 What data circuit speed would normally use the longer pattern lengths, and what is the data circuit bit rate?
Higher speed circuits; 50 kbps to 64 kbps
219.10 What data circuit speed would normally use a 1,048,575 bit pattern length, and what is the data circuit bit rate?
Very high speed T-1 circuits; 1.544 mbps
219.11 What bit rate would you use to test a 9,600 bps data circuit?
A bit rate of 9600 bps, or the closest bit rate available, to test the maximum output of the equipment
219.12 What bit rate would be used to perform a bit error rate test on a 64 Kbps data circuit?
64 kbps
219.13 What subsection in the receiveing section of the bit error rate test set must be synchronesed with the received pattern from either the bit synchronizer or the distant end?
The pattern generator
219.14 What is one of the major problem encountered in making bit error rate tests?
The detection of an "out of sync" condition by the test set receiver
219.15 What should you know about synchronization in order to interpret the bit error rate test data correctly?
You need to know how test equipment responds to the out of sync condition
219.16 What type of connectors do test sets, designed to operat with data modem, usually use?
25 pin connectors, usually the Electronic Industries Association (EIA) RS-232 type
219.17 What must you check to determin impedance and voltage levels before connection the bit error rate test set to the point of test?
The technical manuals
219.18 What information must be available to you from the bit error rate test set readout or special features?
Information to count the number of errors that occur in a specified number of transmitted bits

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