electronic troubleshooting manual
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electronic troubleshooting manualUsed: GoodCustomer service is our top priority!Please try again.Please try again.Please try again. Please try your request again later. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required. Register a free business account To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyzes reviews to verify trustworthiness. Please try again later. Tom 5.0 out of 5 stars Arrived in near perfect condition. Seller provided great service. Great book for enthusiasts. You need JavaScript enabled to view it. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. All enquiries should be made to the publisher at the address above. This introductory chapter provides an overview of troubleshooting processes and various troubleshooting techniques. It also emphasizes how to prepare and read a circuit diagram, as a first step for troubleshooting. However, sometimes there is a conflict between the expectations of the user and the performance of the instrument. Thus develops the need for troubleshooting and maintenance. The process of troubleshooting requires a systematic fault finding approach. Whenever a fault occurs, two things can happen: If there are no obvious faults, measure the power supply voltage. If it is not the correct value, don’t go any further until you find out why. If the symptoms do not get you to the trouble region, use a signal tracing or signal injection method. These methods are discussed in an upcoming chapter. Tough problems like closed loops, distortion, noise and intermittent, require special troubleshooting techniques.http://www.derma-dts.de/files/deere-ag-sales-manual.xml
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Specialized equipment that you build yourself can also be very useful. For surface mount components, some newer techniques are required. The selection of test equipment depends on the amount of service and the type of service. Some of the popular test equipment are:Experienced technicians often use a type of statistical approach for troubleshooting. For example, if there is some distortion in sound in a speaker, there can be several possible faults for the symptom. From experience the technician knows that a battery will fail more often than a transistor. So the battery would be checked and replaced first. If the power supply voltage is not the correct value, nothing will work well in the circuit. It is best to measure the power supply voltage while it is delivering current to the system. In battery operated equipment, the system should be energized when the battery voltage is being measured. If a wrong power supply voltage is measured in a digital circuit, shut it down immediately. Then use your bench supply to energize the circuit and look for possible damage caused by the incorrect voltage. In some cases a system may be reported faulty, but it could be a case of faulty operation or a system failure may be reported with either very little or misleading information. It is essential that a functional test, checking the system’s actual performance against its specification must be made and all fault systems must be noted. The fault is located first in subsystem and then in a single component in the sub system. This is followed by a thorough functional check on the whole system. The following points are discussed in this aspect: Sometimes specialized equipment are required, such as a high speed scope. The maintenance technician is required to have all this knowledge. Most manufacturers supply the following documents with their manuals: There are data books from all major component manufacturers which can be collected. In this case they should be tested.http://artistalexanderkanevskywinnerinternationalaward.com/clientMedia/file/deere-d-110-manual.xml The reason for this can be a cold solder joint of internal or external connectors that need to be cleaned. When the system fails to give the expected performance, the problem could be in any of these functional areas. Therefore, it is essential to troubleshoot the system in order to isolate the fault to the failing functional area and then to the failing component. The logical approach of isolating a fault is through a process of elimination of the functional areas that are performing properly. Once a failure is isolated, further analysis of the circuitry within this area is carried out to isolate the malfunction to the faulty component. This functional area approach is also called the Block-Diagram approach to troubleshooting. This helps to isolate the failing circuit in the first or second part. When the faulty half is determined, the ageing circuit is split into half for further isolation of failure. This splitting is continued until the failure is isolated to one function or component. They may have feedback loops or parallel branches in a part of the circuit. Hence use of this method is rather restricted. In such systems, it is best to start by checking the common feed point. Alternatively if output is normal (at A or B in fig. 1.3), check after the divergence point. Conversely, if one output is abnormal, check before the common point. The most common example is that of the power supply circuit which supplies dc power to various subsystems in equipment. If any of the inputs is incorrect (at C or D in fig. 1.4), then the fault lies in that particular input circuit. If all are found to be correct, the fault lies beyond the convergent point. For example, if C and D are correct and there is no output at E, the fault lies in unit 3. But if input at C is faulty, the fault lies in block 1 or before that.https://ayurvedia.ch/boss-dr-770-dr-rhythm-drum-machine-manual Since the circuit behaves as a closed loop, any fault within the loop will appear as if all the output blocks within the system are at fault: Feedback paths are basically provided for the following functions: For example, automatic gains control system in a radio receiver. For example, an Oscillator circuit. Each block can then be tested separately without the fault signal to be fed around the loop. In some cases instead of completely breaking the loop, the feedback can be modified at or near the point where it rejoins the main forward path. If the output appears normal, check the feedback path, otherwise, check the forward path. If the problem persists, check the switch in common circuitry. If the problem disappears with this action, check that the circuitry switched out. It is the most important document for the maintenance technician. Usually every assembly in electronic equipment is assigned an assembly number which appears on the circuit board and on the diagram. Commonly used symbols in electronic circuits are shown below in Figure 1.7. A circuit diagram is the most important document for the technician. Many-a-time the circuit diagram of the system or equipment is not ready or not provided by the manufacturer. In that case, the technician has to prepare the circuit diagram. The circuit diagram makes the fault finding process easy. Usually, it is not recommended for larger systems. A larger system is broken into parts (subsystems) and then circuit diagrams for the smaller, suspected systems is drawn to trace the fault. The following points must be noted when preparing a circuit diagram: Split the system into a few functional blocks, which will make a functional working diagram. The specifications of the components are notes taken from the manual or data book given with the equipment. Usually individual boards can be removed in industrial systems as they are of modular construction for easy maintenance. Understand the PCB pattern.https://kuhnelektronik.com/images/8410d-lucent-manual.pdf Place the PCB in front of strong light so that the PCB interconnections are clearly visible. If you look at the back of the PCB, then what you see is the mirror image of the connections as seen from the front. Now, make a sketch of the components and PCB pattern. Start with the supply rail, not the common. Now draw the components connected to the supply lead. The ground or common lead will be easy to identify. Power transistors will be either with the power supply circuit or in the output stage. If one stage gets a bit complicated try starting from another stage like input or output stages following the signal path. After the initial attempt, the technician will be able to identify the nature of the circuit. It is the most important document for the maintenance technician. Commonly used symbols in electronic circuits are shown below: These components are physically interconnected with each other to form any electronic circuit. There are three major techniques to interconnect the components. Let us have a brief overlook of these methods: It is a very slow method and is very cumbersome if a large number of devices are to be connected. There are special wire-wrap metal post sockets for the ICs that have longer posts for wire-wrapping the wire. Also, special tools are needed for wrapping and un-wrapping the wire. The circuit is printed on the board by a series of photographic and chemical procedures. Most of the equipment in practice make use of PCB. They are generally made for completely checked out and working boards, as it is difficult to make wiring changes on the PCB. They are mounted inside a wooden or metallic cabinet with some arrangement of interconnecting the circuit boards. This arrangement is called Edge Connectors. This arrangement provides easy installation and removal of the circuit board in equipment: But it is difficult to put a test probe on the circuit board for making any type of measurement or for troubleshooting.The following table distinguishes between these terms: It gives a clue for problems such as burned spots and places where high voltage arc has occurred. A quick look to the circuit also gives an idea of the condition of fuses and circuit breakers. This would lead you to select the troubleshooting technique. You can locate where the problem is not present so that you can then focus on another location for troubleshooting. After all, the choice of techniques and strategies for troubleshooting totally depends upon the technician. The following points would be helpful for effective troubleshooting: The mains power supply voltage can be either 110 V, 60 Hz or 220 V, 50 Hz. Make sure that a protective ground connection by way of the grounding conductor is or is not provided. The caution statements, warning statements and other information should be read carefully. Check the conditions of all external cables for splits, cracks, twists and so on All these parts together make a complete electronic system. Which technique has to be applied totally depends on the type of system. He should understand the basic functionality of the system. Then he can proceed to analyze the cause of the trouble. However, in practice it is observed that even the best design, manufacturing and maintenance efforts do not completely eliminate the occurrence of failures. There can be various causes and types of failures. For the enhancement of system reliability, it is necessary that the design engineer understands the causes of failure, so as to trace the deficiency in the system. The primary concern is to identify the correct causes of failure and to decide on appropriate corrective action to assure higher system reliability. In spite of all the favorable operating conditions, failures are seen to occur. The less is the occurrence of failure, the more is the reliability of the system. For each component or item, the properties that it must possess in the course of its use are listed. A state of fault is denoted by the term failure. This stage is known as Infant Mortality Period and it has a Decreasing Failure Rate (DFR). The infant mortality period is followed by a steady state failure rate period, which is usually long. This period is known as random failure period or useful life of the equipment and this part of the curve being identified as normal operating life curve. This is a period of ageing and wears out with increasing failure rate. If the characteristics deviate beyond the specified limits such as to cause complete breakdown of the required function, it is called as complete failure. A sudden and complete change in equipment performance is called as catastrophic failure. Such a type of failure is referred to as degradation failure. These failures are encountered mostly with analog systems when some noise or disturbance is present. The symptoms are sometimes described by the equipment owner or user. In an industrial electronic plant, it may be the foreman of the division who uses the equipment. In consumer electronic equipment, the description is often from the customer who owns the equipment. Technicians know that certain symptoms in a system usually mean that a certain component has failed. However, one should avoid basing a complete troubleshooting procedure on the knowledge of symptoms alone. For example, distortion in radio’s output sound can be caused by different reasons such as low terminal voltage of aging battery, overuse of transistor, a tear on a speaker cone and so on. Equipment failures take place due to many reasons. The primary concern is to recognize the causes of failure and to take corrective action to achieve higher reliability. The causes can be classified as follows: These can be eliminated by de-bugging or burn-in process. The failure rate of a component can be calculated by operating large numbers of the component for a known period and noting the number of failures that take place during that period. If one transistor is used in the system, then: For example, if there are 3 transistors which are tested until failure, and the time to failure were 300, 600 and 400 hours. It is measured by testing it for a time period (T), during which faults may occur. The equipment is tested after every repair of fault: If a small system has for components with individual failure rates FR1, FR2, FR3, and FR4 respectively, the total failure rate of the system is: It is the average time required to bring a system from a failed state to an operational state. It is defined as the total corrective maintenance time divided by the total number of corrective maintenance actions during a given period of time. MTTR includes the time taken to diagnose, locate and repair the fault. A state of fault is denoted by the term failure. The first stage is Infant Mortality Period, the second stage being Random Failure Period and the third stage is beyond the useful life period which is the Wear out Stage. Symptoms are generally provided by the user of the equipment. However, the maintenance engineer should not decide the path of troubleshooting on the basis of symptoms alone. The first section consists of a study of various hand tools and testing and measuring instruments which are used in troubleshooting of electronic circuits (analog). Digital troubleshooters are explained in chapter 5. The second section consists of actual testing and troubleshooting of various components and devices (chapter4). This chapter provides a brief overview of tools such as Spanners, Wrenches, Screw Drivers, and Files. Analog multimeter, digital multimeter, oscilloscopes are the basic test and measuring instruments required in troubleshooting to test and measure three basic quantities: current, voltage and resistance. This chapter shows how to use these instruments. Availability of proper hand tools and their prior knowledge is essential for the best troubleshooting results. Some of the tools which are often used are listed below. A torque is exerted which is applied to the head of the bolt or nut. Below are some types of spanners. The opposite ends of the spanner have successive jaw sizes. Both the heads are offset relative to the handle. They are most useful for opening control knobs. These are right angled rods of hexagonal cross section with one short arm and one long arm. They also come as a set in metric or inch sizes. Allen Wrenches are most useful for opening many control knobs. Following are the two types of screw drivers: The handle is usually made of tough, transparent colored plastic and shaped to provide a firm, comfortable grip. The handle has a smooth, semi-rounded heel which fits the palm comfortably. The blade and tip are chrome plated. There are four (No. 1 to No, 4) standard sizes of Philips screw drivers. No. 1 and No. 2 are usually needed. For small and delicate work Jeweler’s screw driver sets are available. The barrel of the handle is knurled with a top finger rest. Filing is the most important skill to be acquired in electronic fabrication. Files are classified according to their length, cut of teeth and cross-section. Following are files of different cross section: In those cases files are very useful to enlarge holes. They are also used to smooth the scratch marks on surfaces. The driver’s handle or covered blade is not enough for insulation. In that case the file teeth should be cleaned using file cleaners. A certain amount of personal opinion is involved in troubleshooting methods. One may prefer to use a voltmeter for troubleshooting problems, another may use oscilloscope leads. Although, a personal choice is always there, the technician should be familiar with all the methods, advantages and disadvantages, limitations, and types of troubleshooting instruments. This instrument facilitates the measurement of DC voltage, AC voltage, DC current and resistance values. With proper accessories it can also measure other parameters like high frequency signals, high voltages and so on. A multimeter is a combination of all these meters which makes it very useful in the field. An analog indication of approximate voltage value is more quickly observed as compared to digital reading. They are less susceptible to extraneous noise. It operates with a permanent magnet moving coil, which can become a DC voltmeter, an AC voltmeter, and DC milli-ammeter or an ohm meter. Sometimes an AC current measuring facility is also present. It is mounted in the air space between the poles of a permanent horse-shoe magnet. Refer to the following figure: The direction of rotation depends upon the direction of electron flow in the coil. The magnitude of the pointer deflection is proportional to the current. In usual meters, the full scale deflection (FSD) is about 90 degrees. A scale plate of a standard multimeter is shown in the following figure: For the direct current measurement, place the meter (ammeter to measure current) in series with the circuit. When the ammeter is included in the circuit, its internal resistance adds up, thereby reducing the current in the measuring branch. Usually, this resistance is small and can be ignored. The meter has to be calibrated in amperes rms (root mean square) for the measurement of sine waves. The moving coil meter has a constant resistance. So, the current through the meter is proportional to the voltage. So, in contrast with the ammeter, the voltmeter is connected in parallel with the circuit whose potential has to be measured. As in the AC current meters, AC voltmeters respond to the average value of the rectified voltage but are calibrated in volts rms for a sine wave. Test probes are short circuited and the ohms adjust control is turned so that the current through the total circuit resistance has a full scale deflection. Sometimes the resistances depend upon the circuit conditions, in that case measure the voltage across the resistance, the current through it and calculate the resistance. Never apply more voltage or current than the amount noted in each position. Look at the scale from the point where the pointer and its reflection on the mirror come together. Select the desired current range and connect the meter in series with the circuit under test. The sensitivity of the meter is different for the AC and DC ranges. If the applied waveform is non sinusoidal (square or triangular) then the rectified type of AC voltmeters is subject to errors. Therefore it is advisable to consult the manufacturer’s chart for the factors to be taken into consideration to get the correct value. Even when using a high grade meter of this type it is difficult to take readings with a precision which is better than about 1 percent of the full scale value. For more precise measurements it would be better if the actual value of the voltage or current could be displayed directly as a numerical value. They have high input impedance and the user has to only set the function switch and read the measurement. The analog signal input might be a DC voltage, an AC voltage, a resistance or an AC or DC current. Thus a digital value is converted to a proportional time duration which in turn starts or stops an accurate oscillator. The oscillator output is fed to a counter which drives a digital readout arrangement in terms of voltage values. An over range digit is an extra digit to allow the user to read values beyond full scale. For example if a signal changes from 9.999 to 10.012 a four digit display will require a change in range and the second measurement will read 10.01V. The 0.0002 will not be read. On a Four and Half digit display this problem will not occur. They are used to perform Diode Checks and Continuity Checks in a circuit. In other words, the diode exhibits a very low resistance when it is forward-biased and an extremely high resistance, when it is reverse-biased. An ohmmeter applies a known voltage from an internal source (batteries) to the measured resistor. Theoretically, this voltage can reach 1.5 V or 3 V. The diode requires a voltage of 0.7 V to become forward-biased. Therefore, if the positive test lead of the ohmmeter is connected to the anode and the negative test lead of the ohmmeter is connected to the cathode, the diode becomes forward-biased. In this case, the ohmmeter reads a very low resistance. If the test leads are reversed with respect to the anode and the cathode, the diode becomes reverse-biased. Then, the ohmmeter reads a very high resistance. Thus an ordinary ohmmeter can be used to test a diode. It is marked on the select switch with a small diode symbol. When the DMM is set to diode test mode, it provides a sufficient internal voltage to test the diode in both directions. The positive test lead of the DMM (in red color) is connected to the anode, and the negative test lead of the DMM (in black color) is connected to the cathode. If the diode is in good working order, the multimeter should display a value in the range between 0.5 V and 0.9 V (typically 0.7 V). Then the test leads of the DMM are reversed with respect to the anode and the cathode. As the diode in this case appears as an open circuit to the multimeter, practically all of the internal DMM voltage will appear across the diode. The value on the display depends on the meter’s internal voltage source and it is typically in the range between 2.5 V and 3.5 V. The first case is more common and it is mainly caused by internal damage of the pn-junction due to overheating. Such a diode exhibits a very high resistance when it is both forward-biased and reverse-biased. On the other hand, the multimeter reads 0 V in both directions if the diode is shorted. Sometimes a failed diode may not exhibit a complete short circuit (0 V) but may appear as a resistive diode, in which case the meter reads the same resistance in both directions (for example 1.5 V). This is illustrated in Figure 3.16. The selector switch is set to OHMs. When the diode is forward-biased, the meter reads from a few hundred to a few thousands ohms. The actual resistance of the diode normally does not exceed 100 ?, but the internal voltage of many meters is relatively low in the OHMs range and it is not sufficient to forward-bias the pn junction of the diode completely. For this reason, the displayed value is higher. When the diode is reverse-biased, the meter usually displays some type of out-of-range indication, such as “OL”, because the resistance of the diode in this case is too high and cannot be measured from the meter. What is important, though, is to make sure that there is a great difference in the readings, when the diode is forward-biased and when it is reverse-biased. In fact, that is all you need to know. This indicates that the diode is working properly. For more compete tests on the operation of a circuit, we need to be able to examine the way in which the signal varies with time. This involves displaying a graph of the signal being examined against a base of time, and the instrument employed for this is the Oscilloscope. Multimeter can detect the presence of signals and if the shape of the signal is known the average, peak, rms or peak to peak can be calculated. However, if the waveform is not known, then this is not possible. Noise may be superimposed on the signal and the multimeter will not be able to give the proper information. The oscilloscope gives a true and clear picture of the waveforms. The controls can be present in some different form than shown, but they have to be present in the oscilloscope. After switching on the instrument, wait for a while until the CRT heater warms up. Turn the Brilliance control to clockwise direction until you observe a horizontal line of the trace on the screen. With these settings, a light spot should appear on the screen moving slowly from left to right. Adjust the vertical and horizontal position controls until the trace appears. Unplug the mains and check the fuses. Focus control is used to get the line as thin as possible. Reduce the Brilliance setting to a comfortable viewing level. Probes connect the measurement points in the device under test to the inputs of the oscilloscope. The displayed waveform on the oscillator will become triangular in shape because the capacitor is unable to charge and discharge fast enough through the amplifier load resistor to be able to follow the 10Mz square wave. This probe is usually arranged to act as a divide by ten attenuator and the circuit arrangement is as shown in the figure below: To balance up the capacitive reactance a small series capacitor is connected across R1.Now, when the probe is used to examine the video amplifier circuit, it presents an effective reactance of around 3K at 10Mz and will therefore have much less effect on the signal being examined. This is usually achieved by adjusting the small compensation capacitor in the probe to produce the correct results on a square wave input. Most oscilloscopes provide a square wave test signal for setting up input probes. This signal is applied to the probe input and the probe capacitor is then adjusted to give a correct square on the screen. In a square wave input this will give rise to overshoot on the edges of the square wave as shown in following figure: Unfortunately oscilloscope probes need to be calibrated before they are sued to ensure that their response is flat. There is a built in calibrator on virtually every oscilloscope for this purpose. It provides a square wave output, and there is a small preset adjustor on the probe. With the oscilloscope probe connected to the output of the calibrator the shape of the waveform displayed on the screen should be adjusted until it is perfectly square. If the high frequency response of the probe is down then the edges of the square wave will be rounded. If it is up then the square wave edges will show overshoot. This count is multiplied by the setting of the volts per centimeter switch. This is merely the horizontal distance between the two identical points on the neighboring waves. One signal is fed to CHANNEL1 input and the other to CHANNEL2 input. The CH2 trace is then moved to place it over the CH1 trace. The X position control is then adjusted to move the point where the CH1 trace crosses horizontal axis to line up with the left hand vertical line. The total period of one cycle of CH1 waveform is also measured: This produces a display which is generally referred to as Lissajous figure. With this mode selected one signal is applied to the CH1 input and the other to the CH2 input. It is also assumed that the deflection sensitivities of X and Y circuits of the oscilloscope are the same. If the signal amplitudes or deflection sensitivities are not identical then the resultant image will be stretched in a direction with higher sensitivity. The design of oscilloscopes has evolved slowly from early instruments which were used to simply view a waveform, to oscilloscopes with calibrated ranges and graticules (grid) on the display to enable measurements to be made, up to the modern digital storage oscilloscope (DSO) which have many advanced measurement functions built in as standard. The latest designs now use digital LCD displays instead of the tradition CRT (cathode ray tube) and are putting even more measurement power in the hands of the engineer in ever more portable instruments. The oscilloscope is still evolving, the latest step is the scope meter which combines the functions of an oscilloscope with those of the DMM in one instrument.