Electronic troubleshooting manual pdf

The line indicates the n side. A line or dot placed on the diode by the manufacturer indicates the cathode side. When the end of the diode with the band is connected to the positive side of the power source, it will be reverse-biased.

To test a diode, the troubleshooter can use either an ohmmeter DVM or a diode or transistor checker. Figure 1. Most types of diodes can be checked by using an ohmmeter. If any doubt exists after the ohmmeter check, it is recommended that a new diode be substituted. Also, keep in mind that a low resistance reading both ways is common when the diode is tested in the circuit.

To be sure that the diode is good, unsolder one lead and check the diode again with the ohmmeter. Keep in mind, when you replace a diode, that a diode will only block a certain amount of voltage in the reverse direction. This is called the piv rating, where piv is the acronym for peak inverse reverse voltage.

Never exceed this voltage rating, or else the diode will be destroyed. Although there are numerous types of diodes—zener, light-emitting, photoconductive, varactor, and tunnel—each has its own unique characteristics. For example, zener diodes are special diodes that can operate in reverse bias. In reverse bias the zener diode does not conduct until the voltage threshold, or breakdown voltage, is reached, and then it conducts at a relatively constant voltage.

This operation allows the zener diode to act as a voltage regulator that can be used for regulated voltage power supplies. The transistor is actually made up of two diodes back to back. The first section is called the emitter. The middle section is called the base.

The last section is called the collector. A troubleshooter should understand the reason why a transistor amplifies. Also, the collector base has high resistance to current flow, or is reverse-biased. The negative potential of the battery forces the electrons in the emitter to flow into the base region. Very few of these electrons bond with positive holes, since most electrons continue on through to the collector region.

This is due to the strong positive attraction of the battery. The electrons complete the circuit by returning to the battery supply. Keep in mind that new positive holes are being pulled into the base region from the battery when electrons fill the holes. Since the collector region has a higher value of resistance than the emitter region, any current change in the emitter will cause proportionally a greater change in the collector. A signal passing through its transistor will be amplified.

The amount of signal amplification can be controlled by regulating the amount of electron flow into the base region. The amount of electrons supplied to the base region determines the amount of electrons available to the collector region. The regulation of electrons into the base region is called biasing.

In a transistor, the forward bias or emitter-to-base bias determines the amplification of the transistor. The forward biasing of a transistor can be controlled by increasing or decreasing the voltage or resistance at the emitter-base region see Fig.

The basic operation of current flow in the pnp transistor is very similar to that of the npn except that instead of current flow by electrons, the current flow in the pnp transistor is completed by holes. The positive force from the battery forces the positive holes from the emitter through the base- collector region and back to the negative side of the battery. Here again, as with electrons in the npn transistor, a small number of holes bond with electrons in the base region, but the majority of these holes continue on into the collector region.

Conduction takes place by hole current from emitter to collector. Electron flow is opposite to hole flow conventional theory. Therefore, electron flow in this circuit is considered to travel in the opposite direction, or from collector to emitter. Do not let this explanation of hole current confuse you; basically, the main function of both transistors in the circuit is the same.

Both transistors amplify Fig. The three basic circuit configurations of transistors are the common base, common emitter, and common collector. Each circuit configuration has its own unique characteristics. TABLE 1. Transistors are usually tested either by a transistor checker or by an ohmmeter. Keep in mind that a transistor is actually two diodes back to back and, therefore, can be checked accordingly. Now the transistor is forward-biased, and a low resistance reading should be read.

Reversing the leads will reverse-bias the emitter-base regions, and the ohmmeter will show a high-resistance reading. The base-collector regions are checked in the same way.

Two highs indicate an open transistor; two lows indicate a shorted transistor out-of-circuit test. Transistors can be checked while in or out of the circuit in this manner. It is recommended that a transistor that has checked out defective in the circuit be taken out of the circuit and checked again before being replaced. Some kind of reading should result on the ohmmeter scale. Now short-circuit the base lead to the emitter; the resistance on the meter scale should increase.

When the base lead is shorted to the collector, the resistance on the meter scale should decrease Fig. The field-effect transistor FET is a special transistor used frequently in electronic circuitry. Although its outward appearance is similar to the bipolar transistor npn and pnp , the construction is different.

The FET consists of three terminals—source, gate, and drain—which correspond to the emitter, base, and collector of the bipolar transistor Fig. The gate is a diode junction that is reverse-biased rather than forward- biased as in the bipolar transistor.

Therefore, the gate has very high resistance, allowing for a very high input impedance desired in many circuits. Two high readings indicate an open transistor, and two low readings indicate a short circuit. The ohmmeter reading between the source and drain shows a low resistance in either polarity in a good transistor.

Two highs indicate an open circuit Fig. The current flow in a p-channel is reduced by applying a positive voltage and increased by applying a negative voltage. The depletion type conducts at zero bias and is reduced with reverse bias. With enough reverse bias, it can be cutoff.

The depletion-enhancement type has some conduction with zero bias. Current is reduced with negative bias and increased with positive bias.

They are also sensitive to static electricity and must be carefully handled. For this reason, the gate is kept short-circuited to the source by twisting their leads together during shipping and handling or by a spiral short-circuiting spring. There should be zero resistance between the gate and source or drain.

A reading on the ohmmeter indicates a short circuit. To check the drain-source condition, place a kW resistor from the gate to drain.

Note, however, the best test is by substitution or by use of test instruments Fig. There are several different testing techniques.

Many of these can be used to directly or indirectly test the performance of a transistor. Transistor cutoff Voltage readings can be very useful in determining transistor circuit action. For example, the transistor in Fig. If the transistor is open, or not conducting, the transistor will not draw current; and the voltage at the collector will not be 6 V but the full, source voltage of 10 V.

If the transistor is short-circuited, the transistor will draw excessive current. This will load down the circuit. Often, transistors can be checked by simply applying a combination of heat and cold. First, apply heat by using a hot blower on the suspected transistor. If the transistor is restored to normal operation, the transistor can be diagnosed as defective.

Thermally intermittent transistors are defective transistors that usually break down after lengthy operation.

A rise in temperature increases the current in the transistor; this increased current conduction in turn produces more heat that causes the transistor to draw even more current. Eventually the transistor destroys itself. This sequence is called thermal runaway. Remember, do not be too eager or determined to disable the transistor. This technique is used only for suspected thermally intermittent transistors.

Never apply too much heat to a transistor, especially specialized or sensitive ones, or else needless damage will result. Signal tracing can also be used to isolate a particular defective transistor. For example, if a signal is injected into each stage of a malfunctioning transistor receiver, starting at the speaker and working backward, the defective open transistor will prevent the signal from reaching the speaker.

The transistor substitution technique can be effective in determining a defective transistor. Keep in mind that when you substitute a transistor, be sure to use a similar transistor. This can save the troubleshooter valuable time. Another technique to determine whether a transistor is operating is to short-circuit the base to the emitter, which cuts off the transistor Fig. A noticeable difference in the overall operation of the equipment should result if the transistor is working.

If no noticeable difference is indicated, the transistor is most likely defective. Use caution when you do this test, and make sure you do not short- circuit the base to the collector, since this will cause the transistor to draw excessive current and destroy itself. Also, this method is only useful for certain circuit operations, such as amplifiers or oscillators. The transistor cutoff technique can be compared to locating a bad spark plug wire on a car. While the automobile is idling, each plug wire is lifted off for a second and the idling operation of the engine is noticed.

If the removed spark plug wire causes the engine to idle more roughly, the plug is good; but if the performance of the engine is unchanged, the plug wire is probably defective. Never overheat transistors. Use a heat sink. Use a W, or lower, solder iron. Use an exact or recommended replacement type.

Identify E, B, and C positions. The silicon-controlled rectifier SCR is formed when three diodes are arranged back to back Fig. The SCR acts as a rectifier, except that conduction in the forward direction can only take place when sufficient voltage triggers the gate, at which time the SCR conducts as long as sufficient holding current is maintained. The SCR is a popular device used in burglar alarms and automatic control circuits. It can best be checked by substitution or use of an ohmmeter.

Zero ohm indicates a short-circuited SCR. Integrated Circuits Although the actual construction of an integrated circuit IC is complicated, the process of checking ICs is much easier to understand. The three basic types of ICs are dual-in-line type, round type, and flat type. The IC basically consists of many micro-size components.

One small IC may consist of several resistors, capacitors, diodes, and transistors, all connected into a micro circuit. They are hermetically sealed in a ceramic or plastic package. The two basic methods of IC construction are called monolithic and hybrid. The hybrid, however, is custom-made, and this involves manufacturing the different circuits of the IC separately and then assembling them on the substrate. The approach to testing either IC type is the same.

Courtesy Sylvania, Inc. Logic pulse probe The first step in troubleshooting an IC is to use your senses. Look for obvious problems such as corroded, defective, or damaged pins, sockets, or solder connections. Make sure the IC is completely inserted in its socket. Check the component identification number of the IC with those of the manufacturer to make sure the correct IC is in the circuit and is correctly positioned. Touch is one technique that many service troubleshooters use.

A hot IC is a good indication of a defective or short-circuited component. Most IC components should feel cool to warm when touched.

As stated before, a suspected thermally intermittent component can be checked by first heating the component with a hot blower—noting the performance of the circuit—and then cooling or freezing the component. The defective thermally intermittent IC should break down when heated but operate again when cooled off.

Voltage checks can be performed easily with a voltmeter or an oscilloscope. An incorrect voltage reading probably indicates a faulty IC or surrounding component. The capacitor bypasses the signal around the IC Fig. If the signal increases when the IC is jumped with the capacitor, the IC is probably defective.

Courtesy Motorola, Inc. Any suspected IC should be replaced by a similar known good IC. This technique of substitution saves valuable time for the service technician. Realistically speaking, troubleshooters do not rely solely on this technique because it would require having a large inventory of ICs on hand, which would be costly. Also keep in mind that if the root of the problem is not a bad IC, replacing a bad IC with a good one could destroy the good one.

Many ICs are mounted on circuit boards, and it is often more practical to simply replace the entire board. IC testers and kits are available to test ICs; however, they may require the IC to be checked while out of the circuit. Also, special multipin clips can be used with a comparator box. These testers and kits can be very handy but are often expensive. The logic digital IC probe is probably one of the most important test instruments used by troubleshooters. This small, handheld probe is generally used to test logic pulses and levels.

The probe contains a complex circuit that identifies, through use of light-emitting diodes LEDs high or low , operating logic-level responses. Like the voltmeter, the logic probe is applied to each IC pin or test point. Courtesy Hewlett-Packard. If you know what the input and output values of the IC are supposed to be, you can measure these values and generally conclude whether the IC is good. This way of thinking about the IC often eliminates the need to understand the complex internal structure of the IC.

Digital logic circuits usually have two logic levels: 0 or 1. Connecting negative or positive voltages can determine whether switching occurs. A signal-tracing method using an oscilloscope is generally preferred to voltage-resistance checks, since true IC operation is dependent on the dynamic operating characteristics of the circuits.

The signal-tracing method will be explained in greater detail in later chapters. Order the exact replacement. Insert or position the IC exactly as the original IC. It is extremely easy to insert an IC backward! When you insert a dual-in-line pin IC into the socket, it is easy to miss and smash at least one of the 16 pins. Make sure all 16 pins are aligned properly before you press the IC fully down into the socket. Never overheat an IC. Do not overuse solder; prevent overflow of solder onto the board.

This overflow can cause bridging among adjacent pins and components. Always use desoldering wick or IC suction bulbs to remove excess solder. Electron Tubes Since electron tubes are rarely used today, little mention of their theory will be made.

Electron tubes are found in some industrial and military applications and in a few guitar amplifiers. Some guitar players prefer the more hollow sound that electron tube amplifiers tend to produce as compared to semiconductor amplifiers. Basically, besides the CRT, the troubleshooter might occasionally run into other tubes such as the diode, triode, tetrode, pentode, gas-filled, and multielement tubes. The diode tube consists of a negative cathode and a positive plate.

The negative cathode, when heated, gives off electrons; and conduction takes place. The process of giving off electrons from the cathode is called thermionic emission. When the polarity is reversed, no thermionic emission takes place and no current flows. This valve-like action serves as a one-way gate and is, therefore, used as a rectifier.

The number of electrons that reach the plate from the cathode in the triode tube is controlled by placing a fine-mesh wire called a grid. This control grid is made negative in relation to the cathode. The more negative the grid, the less the current flows; the less negative the grid, the more the current flows.

Cutoff is the point where the grid is made too negative and current flow stops. Saturation is the point where the grid is at the least negative point and current flow is at a maximum between grid and cathode.

In order to prevent interelectrode capacitance, an undesired effect in the triode, a second grid, called a screen grid, is added in the tetrode tube.

When increased performance under certain applications is desired, a third grid is added. It is called a suppressor grid. The pentode that contains this grid eliminates secondary emission uncontrolled acceleration electrons near the plate by controlling these accelerated electrons.

Power tubes are basically for high-power amplification. Gas tubes are often filled with nitrogen or mercury vapor and are used in high-current applications.

The thyratron tube is a common example of a gas tube. Multielement tubes are tubes consisting of two or more tubes enclosed in the same glass envelope. The pentagrid converter is a common example of a multielement tube. It consists of both the local oscillator and mixer stages in a receiver. Substitution Even though electron tubes are rarely used today, you may still encounter them, especially in servicing old hybrid televisions, computer monitor CRTs, and old industrial and communications equipment.

To examine the quality of a tube while the circuit is operating, use the plastic end of a screwdriver. Gently tap the top of each tube while listening or watching the performance of the circuit such as in a radio or television. Keep in mind that a loose connection or poor soldering connection in the same area could cause the same problem.

Another way to quickly examine the quality of some tubes is to visually see if the heater is lighted. If the heater is open, no glow will be produced and the tube will not operate.

An ohmmeter can also be used to check the heater. Although the tube tester can be a helpful instrument for the troubleshooter, it can also be a handicap. Undoubtedly, the tube tester will indicate that many of the tubes need to be replaced but will often fail to pinpoint the one tube that is causing the problem. Valuable time and money can be saved by understanding the function of each tube in a circuit and how to properly use a tube tester. For example, tube testers cannot match the operating conditions of the circuit.

They cannot adequately measure interelectrode capacitance. Also, oscillators, limiters, and high-voltage tubes where characteristic curves are critical are difficult to test on the tube tester. Remember, if the tube failed because of a circuit problem, the substitution of another new tube will only ruin the new tube. For example, when you are servicing an electronic device, if a rectifier tube is found short-circuited, also look for a short-circuited filter capacitor.

Perhaps the filter capacitor caused the rectifier tube to short-circuit. Also, before you replace any tube, it is a good idea to visually inspect the area for charred resistors or any other problem that could have caused the tube to fail.

Unlike the transistor, which could theoretically last forever, the life of an electron tube is limited because the cathode simply wears down and, with time, emits fewer and fewer electrons. Also, mechanical vibrations, excessive heat, and current all contribute to tube breakdowns. When you are replacing a tube, be sure to use the exact replacement or recommended substitute and make sure the tube socket is clean and free of corrosion. Also, be careful not to bend the tube pins. Ultracapacitors Ultracapacitors, also called double-layer capacitors DLCs , are very powerful capacitors that can store over times more electrical energy than conventional capacitors.

They operate by using nonreactive, porous plates with an extremely high surface area in an electrolytic solution through the movement of charged ions. Electrical energy is charged electrostatically. Ultracapacitors offer many benefits over conventional capacitors and batteries, such as quick charging, high energy, low weight, high reliability, long life, and low maintenance. Maxwell Technologies. One of the more popular applications of ultracapacitors is in the automotive industry.

Ultracapacitors are being used in regenerative braking systems, diesel-electric buses, and in conjunction with electrolytic batteries for hybrid vehicles. Ultracapacitors can operate more efficiently and longer than batteries in wide temperature ranges. An ultracapacitor also can operate at any voltage within its voltage rating, and unlike the battery, it can be stored without any charge and quickly recharged. The use of ultracapacitors in conjunction with batteries can provide excellent power and energy for hybrid vehicle applications.

They can extend conventional lead-acid battery life by adding power during peak loads and help provide quick acceleration and regenerative braking. It also has low weight, low current leakage, and excellent cycling reliability, making it suitable for other nonautomotive applications, such as backup power supplies during power outages for industrial and medical facilities. Like other electrical components, ultracapacitors can experience faults such as internal shorts, open circuits, cell leakage, and material breakdowns, often due to internal stresses from excessive vibration, thermal expansions, damage, or abuse.

Common tests for ultracapacitors consist of charge- discharge and measuring equivalent series resistance ESR. Parameters such as initial working voltage, discharge current, minimum voltage under loads, voltage after load removal, and the time to discharge from initial charge to a minimum voltage can be measured to test the quality of ultracapacitors.

Appendix L gives detailed test procedures from Maxwell Technologies for checking ultracapacitors. Inductors An inductor is basically an electromagnet that is used in many applications, such as transformers, up and down voltage steppers, filters, oscillators, phase shifters, integrators, and differentiators. The inductor basically opposes any current changes, and this is often referred to as inductance. The inductor creates a magnetic field that induces a counter electromotive force EMF.

Inductance L is measured by the unit henry H. Types of inductors include air core, iron core, ferrite core, fixed, and variable. One common application of the inductor is in filtering circuits. At a basic level, inductors pass low frequencies and block high frequencies. Capacitors, on the other hand, often pass high frequencies and block low frequencies.

Therefore, when both inductors and capacitors are used in conjunction, they can act as a filter. For example, in a sound system, an inductor could be used to block high-frequency music to the woofer speaker, and the capacitor could be used to block low- frequency music to the tweeter speaker. A combination of the inductor and capacitor can be used to provide proper midrange frequency music to the midrange speaker.

Many inductors can be tested using an ohmmeter. While the windings of an inductor are often shorted, open circuits tend to account for the majority of defects. When you use the ohmmeter, an inductor, depending on the size and number of windings, should have resistance from about zero to a few hundred ohms. Larger inductors with many turns of wire generally measure some resistance. A shorted inductor would measure zero resistance. An open inductor would measure infinite resistance.

Therefore, it may be necessary to use an inductor analyzer to check the inductance. Which of the following is not an example of a source of breakdown?

Heat B. Moisture C. Poor installation D. Animals and rodents E. Which of the following is not one of the senses commonly used by service troubleshooters?

Sight B. Hearing C. Touch D. Taste E. A hot, smoky product or device is often a sign of A. A short circuit B. A ground C. An open circuit D. All the above E. A circuit that has infinite resistance is called A.

Voltage measurements are often taken by using a voltmeter or A. An ammeter B. An oscilloscope C. An ohmmeter D. A wattmeter E. Signal injection or tracing is a method commonly used in troubleshooting A. Electric motors B. Residential wiring C. Industrial wiring D. Radio E. Bypassing B. Substitution C. Bridging D. A cold solder connection can best be repaired by A. Substitution B. Bridging C. Resoldering D. Cooling E. Discussion of defect with customer B.

Acquisition of service information C. Selection of troubleshooting technique D. Repairing of the problem E. All the above The type of diagram that illustrates the component parts of a product or device is called a A.

Line drawing B. Schematic diagram C. Blueprint D. Pictorial diagram E. Schematic print A component having no continuity would have A. Zero resistance B. Infinite resistance C. Both A and B D. None of the above A good fuse will have A. Small resistance D. Both A and B E. The physical size of a resistor, which determines the ability of the resistor to absorb heat, is rated in A. Ohms B. Volts C. Watts D. Farads E.

The new fully charged lead acid storage battery should measure A. Over 12 V B. Capacitors can be tested by A. An ohmmeter B. A spark test C. Only B and C E. In order to make a p-type crystal, A. A pentavalent of gallium is added B. A trivalent of indium is added C. A pentavalent of antimony is added D.

A trivalent of arsenic is added E. The term acceptor is referred to in the A. Addition of pentavalent to the crystal B. Actually a transistor is A. One diode B. Two diodes back to back C. Three diodes back to back D. Four diodes back to back E. High-voltage gain and low-current gain are characteristics of the A.

Common base circuit B. Common emitter circuit C. Common collector circuit D. Both A and C E. If the operating voltage at the collector of the transistor were much lower than normal, one could suspect A.

A defective filter B. An open resistor C. An open transistor D. A short-circuited transistor E. To cutoff a transistor for troubleshooting purposes A. Short E and B B. About Contact Privacy Policy Disclaimer. Forgot your password? Get help. How to Download? We have collected all this information from the internet these all are already published freely. But if you are the owner of any of these contents then please contact us. We can remove anything immediately at your single request.

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