RADIO MECHANICS

As to the AC function of the voltmeter, the lowest voltage selector setting is 10 V. Similar readingprocedures are applied toAC voltages as for DC function. An important point to remember is that the type ofvoltage to be measured must correspond to the meter function. The meter will not work properly if the wrongfunction is set by mistake. While measuring unknown voltages, it is best to set the voltmeter to the highest voltage setting. Veryhigh voltage damages the meter if the applied voltage exceeds the voltage capacity set by the selector. If themeter does not respond to a higher setting lower, set the voltage of the selector gradually.DCmA Meter The direct current milliammeter (DC mA) is equally important in troubleshooting. It is used to measuresmall current flowing in a given circuit component. 0-250 scale is used to measure current. There are fourselector settings to choose from. They range from 50 uA to 0.25 A. The procedure of reading the scale forcurrent flow resembles the one for voltages. While interpreting current readings, bear in mind that 0.25 A(Ampere) is equal to 250 mA (milliampere) and 50 uA equals 0.05 mA.Unnumbered Scale Divisions Reading unnumbered divisions should be as easy as numbered scales. Looking closer at the ohmmeterscale, you can notice bigger divisions in bold lines and smaller divisions between them. The figure below showsthe needle pointing between the bold marks of 10 and 20. If the pointer rests in any of the smaller gradeswithout numbers, each division should be counted. In the example, the reading is 15. Since there are only 5smaller grades between 10 and 15 each grade is counted as 1. In the next example, there is a reading of a voltmeter scale. The needle is pointed at the second divisionafter 5. Since there are only 5 grades between numbers 5 and 6, each small grade is counted by 0.2 volt. Thusthe reading is 5.4 volts. 13

Activity 2AC and DC Voltage MeasurementsMaterials Needed: 1 transformer 1 cord with plug 4 batteries 1.5 V each 1 V.O.M. 1 connecting wiresProcedure:1. Prepare (1) transformer 750 mA, 3 to 12 volts, 220 VAC (PR1).2. Connect the AC cord to the primary transformer, as shown below.3. Measure the different secondary AC voltages and record the result in Table 1. Set the range selector to the 50 VAC range. Follow this combination in measuring AC voltages.AC Voltage Measurements: Table 1 Combinations AC Secondary Voltages 0-3V 0-4.5 0-6.0 0-9.0 0-12.0 14

Sec z V.O.M. PRi 12 z z 0 50 z 220 9 z z 50 VAC 6z z z zz 4.5 z 0 3z 0z Transformer with AC cord connected to 220 VACDC Voltage Measurement Measured Value DC Voltages Table 2 Combinations Series aiding Series opposing Parallel connection Series parallel Combination0 10 V 0 10 V_10 VDC _10 VDC + +_+ -+ -+ -+ -+ Series Aiding Series OpposingProcedure:1. Set the range selector to 10 VDC.2. Connect the batteries in series aiding, series opposing, parallel connection, and series parallel combination. 15

3. Measure the DC voltage as indicated. Observe correct polarity. Record the measured value in Table 2.4. Do the same procedure in other combinations as shown below.0 10 V_10 VDC + 0 10 V _10 VDC -+ + -+ -+ -+-+ -+ -+-+Parallel Connection Series Parallel CombinationSelf-check:1. What is the difference between series aiding and series opposing when it comes to measured value?2. Which is the normal connection of battery that we commonly use in our radio receiver?3. What is the difference between primary and secondayAC voltages?4. What is the purpose of using a transformer?LET’S SUMMARIZE Radio and television service work is based primarily on the proper use of meters. It is thereforeessential that the technician knows the test instruments and how to use them. This module provides a compre-hensive study of various types of testing and measuring instruments such as the ohmmeter DC voltmeter,ACvoltmeter, DC micro-ammeter, DC milliammeter and DC ammeter. Knowledge of the basic tools and instruments and their use gained from this module is essential toachieve success in your chosen career, whatever field of interest you choose. Radio and TV servicing,communication, industrial or computer electronics. 16

POSTTESTDirections: Read each statement carefully and choose the letter of the best answer. Write it on the blankbefore each number._____1. Use to cut soft wires and component parts. a. long nose pliers b. diagonal cutters c. mechanical pliers d. electrical pliers_____2. It removes the insulators from the hook up wire. a. soldering aid b. soldering iron c. wire stripper d. desoldering tool_____3. Tool used to solder and unsolder the components on a printed circuit board. a. soldering gun b. soldering iron c. wire stripper d. desoldering tool_____4. An instrument used to measure voltage. a. ammeter b. voltmeter c. ohmmeter d. wattmeter_____5. A handtool used in soldering high wattage equipment. a. soldering lead b. soldering iron c. soldering pencil d. soldering gun_____6. An instrument used in measuring current. a. ammeter b. ohmmeter c. voltmeter d. wattmeter 17

_____7. What does V.O.M. mean? a. volt ohmmeter b. volt ohm milliameter c. voltage ohmmeter d. wattmeter_____8. An instrument used in measuring resistance. a. voltmeter b. wattmeter c. ohmmeter d. ammeter_____9. A handtool used in desoldering components. a. long nose pliers b. diagonal cutter c. electrical pliers d. soldering pump_____10. It must be observed when measuring DC voltage and DC current. a. negative b. positive c. polarity d. meterKEY TO CORRECTIONPretest / Posttest1. b2. c3. d4. b5. d6. a7. b8. c9. d10. c 18

Radio Mechanics Fourth Year Module 4 Small But Terrible Electronic ComponentsWhat this module is about This module is about small electronic parts which are the building blocks of electronic equipment andappliances. These electronic equipment and appliances are made up of circuits. Circuits are made up ofelectronic components. Components and their interconnections are represented in diagrams by their sche-matic symbols. Technician always refer to schematic diagrams when troubleshooting and repairing equipment.We cannot read and interpret diagrams without knowing component symbols. As electronic students andwould-be technicians, it is a must for you to learn the symbols and functions of the basic electronic compo-nents. After going through this module, you are expected to do the following:1. Identify the different electronic components, their functions and uses.2. Determine the resistance values of carbon and film-filled resistors through color codes.3. Calculate the maximum and minimum value of resistors through color codes.4. Draw schematic symbols of electronic components.5. Test and measure effective and defective electronic components.How to learn from this module For maximum benefit from this module, you have to follow strictly the instructions.1. You must work on this module in the sequence its contents are presented.2. After reading the objectives, answer all the questions in the pretest as honestly as you can.3. Check your answers by comparing these with the key to answers in the last part of this module. Ask your teacher the test results.4. Read and understand every lesson as much as you can. Try to do the given activities and do the self-check to determine whether you understood what you have read.5. Answer the posttest and compare your answers with the key to answers. You must get a score of at least 80% in order to move on to the next module. If you get less, you have to go through the module again. 1

Reminder: Be honest in answering and checking the pretest. Remember, you are studying by yourself. Yourlearning depends totally in you.PRETESTI. Directions: Give the component and its function or use as required. Component Function / Use1. Switch __________________________________2._________________ Converts electrical energy to sound energy.3._________________ Generates and amplifies signals.4. Transformer __________________________________5. Inductor __________________________________6. ________________ Stores charge in its dielectric.7. Diode __________________________________8. ________________ Regulates the flow of electric current.9._________________ Protects the circuit from overload.10. Integrated circuit __________________________________II. Directions: Write the name of the following electronic components illustrated in schematic symbols.d1. 69 _________________ _________________2. _________________ _________________m3. _________________ _________________4. _________________5. _________________6. _________________ _________________Y7. K8.9.10. A 2

Lesson 1 Schematic Symbols of Electronic Components As previously stated, electronic components are the building blocks of all electronics equipment andappliances. These equipment and appliances were illustrated in schematic diagrams. You can interpret sche-matic diagrams easily if you know the schematic symbols of electronic components. Considering the many applications of electronics, only a few of the basic types of components areused to represent all kinds of equipment and appliances. Each type has a specific function and use. Followingare some of these electronic components and their uses and symbols.1. Resistor ( R) is an electronic component that regulates the flow of electronic current and produces specific voltage drop in circuit. It is used in bias circuits, coupling circuits, load circuits, tone control and volume control. 992. Capacitor (C) is an electronic component that stores charge in its dielectric. It blocks DC and allowsAC to pass through. It is used in coupling, filtering, and tuning circuits.non polar Tuning Capacitor Trimmer Capacitor Variable Capacitor Vertical Capacitor -+polarized3. Inductor or Coil (L) stores energy in its magnetic field. It blocks AC and passes DC. It is also used in filtering, coupling and tuning circuits. ] 3

4. Transformer ( T) is an electronic component that transfers power or Y signals from the primary to the secondary circuit by means of induction. It is used in power supplies, power isolation, stepping up or down voltages and as coupling between the stages of amplifiers.5. Diode (D) is an electronic component that conducts current only in one direction. It is used as rectifier in power supplies, detector in radio receivers, in switching circuits and as indicator.m6. Transistor (T) is an active electronic component that generates and enlarges (amplify) signals. It is used as an oscillator, amplifier and switch in switching circuits. {7. Crystal (Y) is an electronic component that produces electromotive force (EMF) when made to vibrate and vice versa. It is used as oscillator in radio transmitters and radio receivers, among others.8. The loudspeaker converts electrical signals or sound signals or energy. It is used in all sound producing systems such as the radio, TV receivers and stereo amplifiers, among others. Speaker 4

9. The fuse (F) protects the circuit from overload or excessive current. It is used practically in all equipment and appliances. It is also used in wiring installations. d Fuse10. Switch (SW) is used to open and close the circuit. With the switch we can convenietly connect or disconnect our appliances to or from the voltage source without disconnecting the plug from the voltage source.Rotary switch Slide switch Push button Toggle switch switch11. Integrated Circuit (IC) is an active electronic component that is used as amplifier, oscillator, modulator, demodulator and regulator in digital circuits.Activity 1 Make a compilation of the schematic symbols of other electronic components not included in thismodule. Draw them in a short bond paper and place them in a short folder. Use separate bond paper foreach component. Follow the arrangement of components listed below.Components1. resistors2. capacitors 5

3. inductors4. transformers5. diodes6. transistors7. switches8. logic gates9. electronic instruments or meters10. others - those not included in the listSelf-check: Draw the schematic symbols of the following electronic components with their corresponding lettersymbols.1. fuse 6. switch2. diode 7. transistor3. resistor 8. transformer4. capacitor 9. integrated circuit5. inductor 10. crystal Lesson 2 Resistor Color Codes The characteristics of a resistor of opposing the flow of electric current is its resistance, represented byletter (R). Resistance is measured in ohms Ω, named after George Simon Ohm, a German Physicist. Resistance values of resistors are printed on their sides in numerals in color codes. In wire-woundresistors, resistance values are oftentimes printed on their sides in numeral. Resistance values of carbon-composition resistors as well as film-filled resistors, are printed as color bands around their circular bodies ascolor codes. 6

Resistor Color CodesColor code is the system of using different colors to indicate the resistance values of resistors. Table 1 Colors Used in Resistors and their ValuesColor First Significant Second Significant Decimal Tolerance Figure Figure MultiplierBlack 0 0 1 20Brown 1 1 10 1Red 2 2 102 2Orange 3 3 103 4Yellow 4 4 104 4Green 5 5 105 5Blue 6 6 106 6Violet 7 7 107 7Gray 8 8 108 8White 9 9 109 9Gold 0.1 5Silver 0.01 10No Color 20Memory Guide Table II Numerical Equivalent Color EquivalentBold 0Boys Black 1Rave Brown 2Over Red 3Young Orange 4Girls Yellow 5But Green 6Vilma Blue 7Gives Violet 8Willingly Gray 9 White 7

In Table II, color codes are simplified for easy learning . The memory guide should be memorized. “ Bold Boys Rave OverYoung Girls, But Vilma GivesWillingly.”How to Read the Color Codes of Resistors When reading the colors of a resistor, always start reading from the first color nearest to the end ofthe resistor, and continue as indicated by the arrow. See the figure below. 1234 Figure 1Interpreting the Color Codes of Resistors When using the simplified color code (Table 1), first, memorize the Memory Guide (Table II). Paireach word with its color equivalent and then its numerical equivalent (Table II). In interpreting the colors of a resistor, the first color nearest the end of the resistor is the first digit,the second color is the second digit, the third color is the multiplier or the number of zeroes to be added to thefirst and second digits, and fourth color is the tolerance. See the figure below.Second digit Multiplier First digit Tolerance First color Fourth colorSecond color Third color Figure 2 In the example that follows, we will disregard the fourth color (tolerance color) for a while. This is forsimplicity and for easy learning. However, it will be discussed later. 8

Red (100) Blue (6) Green (5) Figure 3 To determine the resistance value of the resistor in Figure 3, its colors are interpreted as follows: ( SeeTable 1). Green, being the first color band, has a numerical value of 5 in the first significant figure. So, write 5as your first digit. Blue being the second color band, write 6 as your second digit. The number formed is 56.Red, the third color band and serving as your multiplier, has a numerical value of 102 or 100. Multiplying thefirst and second digits (56) by 100 gives you an answer of 5,600. Hence, the value of the resistor is 5,600ohms. 56 x 100 = 5,600 In another way, simply write 2 zeroes after the first and second digits and you get the same answer.Multiplying a number by 100 is the same as adding two zeroes to the right of the number. first digit 5600 2nd digit When the third color band is black, it simply means that you are to multiply the first two digits by one(1). See Figure 4.Brown Black Red red, brown, black 21 x 1 = 21 Ω Figure 4 When the third color band is gold, it simply means that you multiply the first two digits by point one(0.1). See Figure 5. 9

gray gold blue blue, gray, gold 68 x 0.1 = 6.8 ohms Figure 5When the third color band is silver, multiply the first two digits by point zero (0.01). See Figure 6.black silver yellow blue, gray, gold 40 x 0.1 = 0.40 ohms Figure 6Self-check:Give the values of the following resistors:Note: The fourth color is disregarded.1. Red, Violet, Brown, Gold2. Orange, Red, Black, Silver3. Gray, Red, Gold, Gold4. Orange, White, Red, Silver5. Yellow, Violet, Black, Gold 10

Activity 2 Get five (5) resistors (1 watt each) with different color codes. Attach them to a short folder andcompute their color code value. See the following example.Resistor Colors Color Coded Maximum Minimum orange, red, brown, gold Value Tolerance Value Tolerance Value 320 Ω 336 Ω 304 ΩNote: Prepare your folder in the same manner as the given example. Start your measurements from the center in order that all the outer lines are equally distant from the edge of the folder. Lesson 3 Tolerance of Resistors The fourth color band of the resistor represents its tolerance value. Tolerance indicates the permissibleminimum values a particular resistor can deviate from its original color coded value when the said resistor isused in the circuit. There are three colors used to indicate tolerance. They are gold, silver, and body color (no colorused).Rules to Determine Tolerance of Resistors1. When the fourth color band is gold, it simply means that tolerance is 5% above and below its color coded value. In the other words, if this particular resistor is good, the measured value should be within 5% plus or minus its color coded value.2. When the fourth color band is silver, it simply means that tolerance is 10 % above and below its color coded value. 11

3. When there is no fourth color band, it simply means tolerance is 20 % above and below its color coded value. Actually, this type of resistor has only three color bands. The fourth, indicating its tolerance is the same as its body color.How to Calculate the Value of Resistors Considering their Tolerance1. Write down the value of the resistor based on its color code in ohm.2. Compute the tolerance value (in percent) of the color coded value.3. Add the extracted tolerance value to the color coded value. The sum represents the maximum value.4. Subtract the extracted tolerance value from the color coded value. The difference represents the minimum value. For example, calculate the value of the given resistor considering its tolerance. See Figure 7. brown red 1 2 red gold 100 5% Figure 7 - Resistor with gold as its tolerance color.The color coded value is: 12x 100 1,200 ohmsCompute 5 % of 1,200 ohms (converting 5 % into decimals gives you .05) 1,200x .05 60 ohms - extracted tolerance valueAdd the extracted tolerance value to the color coded value: 60 ohms + 1,200 ohms = 1,260 ohms - maximum valueAdd the extracted tolerance value from the color coded value; 1,200 ohms - 60 ohms = 1,140 ohms - minimum value 12

Interpreting the Computed Maximum and Minimum Tolerance Value The value of the resistor, one color code of which is brown, red, gold, is between 1,140 amd 1,260ohms or above 1, 260 ohms considering its tolerance value. If the resistor measured value is between 1,140and 1,260 ohms or above 1,260, the resistor is defective and should therefore be replaced. But if the measuredresistance value is within or between 1,140 ohms and 1,260 ohms, the resistor is good.Self-checkDirections: Calculate the maximum and minimum tolerance value of the following resistors the color codes ofwhich are as follows:1. Brown, Green, Green, No Color2. Gray, Violet, Black, Gold3. Orange, White, Brown, Silver4. Red, Red, Orange, Gold5. Brown, Gray, Brown, SilverActivity 3 Using the same folder and set of resistors in the activity you did in Lesson 2, compute the maximumand minimum tolerance value of the attached resistors. See the given example in Lesson 2 (Activity 2). Lesson 4 Testing Good and Defective Electronic Components Electronic components may become defective due to continued use. Some of these defects may occuraccidentally while others due to overcurrent flowing through the circuit. An efficient electronic technician mustbe proficient in testing electronic components. Electronic components develop various troubles, thus requiringdifferent approaches to test electronic components. Use the VOM (Volt-Ohm-Milliammeter).Testing Resistors with an Ohmmeter of VOM Resistors may develop troubles such as open resistors, increased resistance values and decreasedresistance values. Before testing any resistor in the circuit, do the following:1. Switch off the device or appliance. 13

2. Disconnect or desolder one terminal of the resistor you desire to check from the printed circuit board (PCB). Be careful when disconnecting the resistor from the circuit. Carelessness may result in breaking the printed circuit foil.3. Set your ohmmeter to the appropriate range. When checking resistors of high resistance value, adjust the ohmmeter to the highest range.Test Results of Defective Resistors open change valueThe ohmmeter does not deflector reads infinitely even at the Ohmmeter reading differs muchhighest range. beyond the tolerance value.Testing the Capacitor with an Ohmmeter or VOM Acapacitor may develop trouble like open shorted and weak or leaky. Following are rules to follow intesting capacitors:1. Switch off the power supply.2. To be safe and to protect your ohmmeter from damage, discharge the capacitor before testing. Do this by shortening its two terminals with a screwdriver. Make sure you are handling the screwdriver on its insulated handle.3. Disconnect one terminal lead of the capacitor from the circuit before testing. 14

4. Adjust your ohmmeter to a higher range such as R x 10 K or R x 1 meg.Test Results of a Good Capacitor The pointer deflects to the right and goes back slowlyTest Results of Defective Capacitors to infinity or the original position.Ohmmeter reading needs infinity Ohmmeter reads zero The ohmmeter indicates resistanceeven at the highest range. even at a lower range. to reading.The pointer does not move The pointer deflects to The pointer deflects to the right andto the right. the right and stays there. does not return to infinity.Testing Diode with an Ohmmeter or VOM Before attempting to test a good or defective diode, one thing very important to consider is knowing itsterminals or electrodes. These electrodes are anode (A), positive current-carrier and cathode (K), negativecurrent-carrier. Following are some points to consider in determining the electrodes of a diode. 15

1. Cathode and anode markings are displayed on the body of the diode, as shown in the illustrations.K AK AK AK A2. Sometimes, markings are worn out, hence use a VOM to determine the electrodes. The battery inside the VOM is used to apply forward and reverse bias. In the forward bias, the positive post of the battery is connected to the anode, and the negative post is connected to the cathode. KeA diode -+ battery Reverse bias - the positive post of the battery is connected to the cathode and the negativepost is connected to the anode. KeA diode +- battery3. Knowing the correct polarity of the VOM is a “must”. The polarity of the internal batteries of Asian VOMs such as Standard and Sanwa are opposite to the markings of its test prod sockets. The negative terminal of the battery is actually connected to the positive (+) output jack. The positive terminal is connected to the negative (-) common jack. 00 0 internal batterypositive jack + - +- negative jack 16

Test Results of a Good Diode Note: The VOM we are going to use has reversed polarity. VOM indicates low resistance reading In reversing the leads, VOM shows very high (forward bias) resistance or infinity (reverse bias)Test Results of an Open Diode forward bias reverse bias VOM indicates infinity or high Reversing the lead-VOM still indicates resistance in all ranges. infinity or high resistanceTest Results of a Shorted Diode forward bias reverse biasVOM reads zero resistance in all rangesThe pointer deflects to the right and stays there. Reversing the leads, does not alter the indication . VOM still indicates zero resistance 17

Test Results of a Leaky Diode forward bias reverse biasVOM indicates resistance reading Reversing the leads, VOM still indicates resistance readingTesting Transistors with an Ohmmeter or VOM Practically all electronic equipment and appliances contain transistors. Most of the common troublesof electronic equipment and appliances are caused by faulty transistors. Transistors have three (3) electrodesor terminals; the base (B), the emitter (E) and the collector (C). They are grouped into two types; negative-positive-negative (NPN) and the positive-negative-positive (PNP). Transistors have two junctions betweentheir electrodes - the emitter-base junction and collector-base junction. The symbols below indicate the type oftransistors with their electrodes and junctions.collector-base C collector-base Cjunction E junction E B B emitter-base emitter-base PNPTransistor junction junction NPN Transistor Transistors may develop troubles such as shorted emitter-base, open emitter-base, shorted collector-base, open collector-base, shorted collector-emitter, and leaky collector-emitter. 18

Below are transistors with identification and leads bearing levels. Figure E-1 Figure E-2 Figure E-3 Figure E-4 Figure E-5 Figure E-6The labels are interpreted as follows:Figure E-1 The base and emitter leads are identified through letters. The collector is the transistor body.Figure E-2 The lead nearest to the dot on the transistor body is the collector. The lead next to the body is the base.Figure E-3 The lead nearest to the flat portion of the body is the emitter.Figure E-4 The lead nearest to the tab is the emitter.Figure E-5 The left pin is the base, and the right pin, the emitter. The transistor body is the collector.Figure E-6 The center lead is the collector which is connected internally to the metal tab.Figure E-7 The angular lead is the base.Test of Good Transistors Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6The illustrations above are interpreted as follows:Figure 1 - VOM indicates resistance reading (forward bias).Figure 2 - Reversing the leads, VOM indicates infinity or high resistance (reverse bias). 19

Figure 3 - VOM indicates resistance reading (forward bias).Figure 4 - Reversing the leads, VOM reads infinity or high resistance (reverse bias).Figure 5 - VOM reads infinity or high resistance.Figure 6 - Reversing the leads, VOM still indicates infinity or high resistance.Test Results of Defective Transistors Figure 11. Shorted emitter-base Figure 2 Interpretation of the illustrationsFigure 1 - VOM indicates zero resistance.Figure 2 - Reversing the test leads VOM still indicates zero resistance.2. Open emitter-base Interpretations: Figure 3 Figure 4Figure 3 - VOM reads infinity or high resistance.Figure 4 - Reversing the test leads. VOM still reads infinity.3. Shorted collector-base Interpretations:Figure 5 -VOM indicates zero resistance. Figure 6 - Reversing the test leads, VOM still indicates zero resistance. 20

4. Open collector-base Interpretations: Figure 7 - VOM reads infinity Figure 8 - Reversing the test leads, VOM still reads infinity.5. Shorted emitter-collector Interpretations: Figure 9 - VOM indicates zero reading. Figure 10 - Reversing the test leads, VOM still reads zero.6. Leaky emitter-collector Interpretations:Figure 11 - VOM indicates resistance reading. Figure 12 - Reversing the test leads, VOM still indicates resistance reading. 21

Testing the Transformer with an Ohmmeter or VOM The transformer is an alternating current and voltage changing device through which voltage can bereceived and delivered at either higher or lower value. It has two windings, primary and secondary. These twoseparate windings are wound in an iron core. The primary winding receives the energy or voltage, while thesecondary winding delivers the energy or voltage. Transformers also become defective. Some of these defects are open primary winding, open secondarywinding, shorted primary and secondary winding and shorted iron core and windings.Test Results of Defective Transformers1. Open primary winding. VOM reads infinity or high resistance in all ranges. Iron core 00 0 •• . . R. x.1 PrimaryY• Secondary winding winding . . . .. +. . . . . . - •2. Open secondary winding. VOM reads infinity or high resistance in all ranges. Iron core •• 00 0 PrimaryY• Secondary . . R. x.1winding winding . . . .. • +. . . . . . -3. Shorted primary and secondary windings. VOM indicates zero resistance reading.00 0 Iron core. . R. x.1 •• . . . .. PrimaryY• Secondary+. . . . . . - winding winding • 22

4. Shorted iron core and windings. Iron core VOM 2 VOM indicates both zero resistance reading. •• 00 0 00 0 Y• . . R. x.1 . . R. x.1 . . . .. . . . .. +. . . . . . - +. . . . . . - Primary Secondary VOM 1 winding winding •Activity 4 Report to your teacher in school for actual testing of electronic components. Borrow one (1) VOMfrom your teacher and get a data sheet to record your test results.Self-check:Directions: Read the statements carefully. Check ( 9 ) if the statement is correct, and a cross ( 8 ) if it iswrong.____ 1. It is good practice to discharge capacitors before testing.____ 2. Resistance can be checked accurately in a circuit.____ 3. Resistors may become shorted due to overcurrent.____ 4. If a capacitor is open, the VOM reads infinity even at highest range.____ 5. The battery inside the VOM applies forward or reverse bias to the diode.____ 6. A shorted diode is indicated by a zero resistance reading in the VOM.____ 7. An open-base emitter junction of a transistor is indicated by high resistance in the VOM on either forward or reverse bias.____ 8. Secondary voltage can be measured through a transformer even if its primary winding is open.____ 9. If the primary and secondary windings of a transformer are shorted, the VOM indicates zero resistance reading.____ 10. Atransistor is leaky if there is resistance reading between its emitter and collector.LET’S SUMMARIZE • Electronic components are the building blocks of electronic equipment and appliances. They are small but terrible because they can make even the biggest equipment or machine move or operate. • Some common electronic components are the resistors, capacitors, inductors, transformers, diodes, transistors, crystals, fuses, loudspeakers, switches, integrated circuits and many others. 23

• These small but terrible electronic components may become defective due to overcurrent and long continued use. They may develop defects or troubles like, open, increased or decreased resistance values, shorted, leaky, weak and the like.• These troubles or defects can be identified through voltage and resistance measurements. The volt-ohm- milliammeter (VOM) is the most commonly used instrument to test electronic components for defects.• Through resistance measurement, the condition of an electronic component can be easily determined by the behavior of the VOM’s pointer. The pointer may indicate a resistance reading, a zero resistance reading and an infinity reading. Thus, a technician should be knowledgeable enough to interpret these readings.POSTTESTI. Directions: Fill in the empty boxes with the correct symbols, functions and uses of the indicated electroniccomponents. Component Symbol Functions Uses1. resistor2. capacitor3. inductor4. transformer5. diode6. transistor7. integrated circuit8. crystal9. fuse10. switchII. Below is a pictorial symbol of a resistor. Interpret the colors by labeling them. 4 3 12 24

KEY TO ANSWERSPretestI.1. opens and closes the circuit2. loudspeaker3. transistor4. transfer power from primary to secondary circuit by induction5. blocks AC and passes DC6. capacitor7. used as rectifier in power supplies8. resistor9. fuse10. used as amplifier, oscillator, demodulator, modulator and regulator.II.1. Fuse2. resistor3. diode4. transistor5. capacitor6. crystal7. transformer8. microphone9. loudspeaker10. LEDPosttest]9 Functions Uses Produces specific voltage drop1. Stores electric charge in its dielectric Used in bias, coupling, tone circuits2. Used in coupling, filtering and tuning3. Stores energy in its magnetic field circuits. Blocks AC and passes DC. 25

Y4. 6 Transfers power from primary to Used in power supply to step-upm5. A K secondary circuits or step-down voltage Conducts current in only one As rectifier of power supplies.6. direction Generates and enlarges signals. As oscillator , amplifier and switch7.8. Amplifies or enlarges signals. Amplifier, oscillator and modulator Produces emf when made to vibrate Oscillator in radio transmitter andd9. receiver Protects the circuit from overload Used practically in all electronic10. appliances and equipment Opens and closes the circuit For disconnecting electronic appliances from the voltage source.II.1. first digit2. tolerance3. second digit4. multiplier 26

Radio Mechanics Fourth Year Module 5 Show Me If You Can (Circuit Analysis)What this module is about Congratulations, you did well in the previous modules. How do you feel going through this module?Do you think you are already equipped with the necessary knowledge and skills? I hope so. This module dwells on the application of basic electrical quantities in the computation and analysis ofelectrical and electronic circuits. As the end-user of this module, you need depth of understanding of itscontent and be able to apply it in solving simple electrical problems. It also enables you to understand thecharacteristics of the different electronic components when they are connected in different ways. After going through this module, you should be able to do these:1. Compute resistance in series, parallel and series-parallel.2. Compute capacitance and voltage rating of capacitors in series and parallel connections.3. Compute inductance in series and parallel connections.4. Explain transformer ratio.How to learn from this module For maximum benefit from this module, here are some tips to guide you in learning the differentlessons.1. Work through this module in proper sequence as the contents are presented.2. After reading and understanding the objectives, answer all the questions in the pretest.3. Check your answers by comparing these with the key to answers in the last part of this module.4. Read and understand each lesson well. Perform the activities and answer the self-check to determine the extent of your learning.5. Answer the posttest and compare your answers with the key to answers. You must get a score of at least 80% in order to move on to the next module. 1

PRETESTDirections: Read each statement carefully. Write on if the statement is correct, and off if it is wrong. Writeyour answers on the blank before each number. _______ 1. Current is the same in all points of series- connected resistors. _______ 2. Voltage drop across each resistor increases when they are connected in series. _______ 3. Total resistance rises when resistors are connected in parallel. _______ 4. When one of the resistors connected in series becomes defective, it affects the whole circuit. _______ 5. Each resistor serves as current divider when connected in parallel. _______ 6. Current has only one path to flow in parallel-connected resistors. _______ 7. When four resistors are connected in series, current flowing at R1is the same as that at R3. _______ 8. If three 10-ohm resistors are connected in series, total resistance will be 30 ohms. _______ 9. Only three resistors can be connected parallel to one another. _______ 10. Each resistor in a series circuit acts as voltage divider. _______ 11. Connecting capacitors in series means increasing capacitance. _______ 12. The working voltage of capacitors add when they are connected in series. _______ 13. Capacitance values of capacitors rise when they are connected in parallel. _______ 14. Connecting inductors in series results in a higher inductance. _______ 15. The secondary voltage of a transformer is reduced when primary winding has more turns than the secondary. _______ 16. A step-up transformer produces more voltage at its secondary compared to what is applied across its primary winding. _______ 17. Total inductance increases when the mutual inductance between two coils is series-opposing. _______ 18. Parallel inductors provide higher inductance. _______ 19. More turns of wire in the secondary means higher secondary voltage. _______ 20. Secondary current in a transformer is inversely proportional to the turns ratio. 2

Lesson 1Resistance in Series, Parallel and Series Parallel Connections Resistors can be connected in series, parallel and series-parallel combination. Each connection has itsown characteristic as to voltage, current and resistance.Resistance in Series When resistors are connected in series, they come up with the following characteristics:1. The same current will follow through the components in the circuit. Thus, current total (IT) is; IT = I1 =I2 =I3, etc.2. Total voltage (ET) of the circuit is equal to the sum of the voltage drop of each component. Thus: ET = E1 + E2 + E3...3. Total resistance (RT) of the circuit is equal to the sum of all the resistances connected in the circuit. Thus; RT = R1 + R2 + R3... R1 R2 R3 ET Block Diagram of Resistors Connected in SeriesSample Problem: 9R1 6Ω ET = 12 volts 910 Ω R2 8Ω 9R3 3

RT = R1 + R2 + R3 E1 = I1 x R1( from Ohm’s law) = 6 Ω + 10 Ω + 8 Ω = .5A x 6 Ω = 24 Ω = 3 voltsIT = ET (from Ohm’s law) E2 = I2 x R2 RT = .5 A x 10 Ω = 5 volts = 12 volts 24 Ω E3 = I3 x R3 = .5 A x 8 Ω = 0.5 A = 4 voltsChecking: = E1 + E2 + E3 ET = 3 V + 5V + 4V = 12 V - total applied voltageParallel Resistance In a parallel circuit, components are connected across the voltage source. The current has more thanone path to flow in.Characteristics:1. Each component receives the same voltage, or voltage is common to all connected components. ET = E1 = E2 = E3...2. Total current is equal to the sum of individual current in each branch. IT = I1 + I2 + I3.....3. Total resistance is equal to the reciprocal of individual resistance. Hence, total resistance is lower than thelowest resistance connected. 1 RT = 1 + 1 + 1 R1 R2 R3 ...... 4

we can also use this formula, RT= R1 x R2 ; for determining RT of two resistors connected in parallel. R1 + R2 ET R1 R2 R3 Block Diagram of Resistors Connected in ParallelSample Problem: ET = 12 V R1 R2 R3 912 Ω 9 96 Ω 4 ΩRT = 1 , Substitute the values of R1, R2 and R3. 1+1 +1R1 R2 R3= 1 (Find the least common denominator, LCD)1 + 1+1 I1 = E1 I2 = E212 6 4 R1 R2=1 = 12 V = 12 V 1+ 2+ 3 12 Ω 6Ω 12 = 1A =2A=1 6 12 5

= 1 x 12 I2 = E3 6 R3 = 2 ohms = 12 V 4ΩIT = ET RT =3A= 12 V 2Ω=6A Checking: IT = I1 + I2 + I3 = 1A + 2A + 3A =6AResistance in Series Parallel In computing resistance in series-parallel circuits, the easiest way is to simplify the circuit. One way ofsimplifying a series-parallel circuit is to redraw it in order to identify easily which are connected in series andwhich are connected in parallel.Characteristics of Series Parallel Connections1. The current in series-parallel connected resistor divides in a parallel path and comes together in the series portion.2. In series-parallel connected resistors, voltage is the same in the parallel part, and divides in the series portion.3. Resistance in the series portion increases while in parallel portion, it decreases. R1 R2 R1 R2 R3 R4 R3 R4 ET ET R1and R2 are connected in series.R1and R2are connected in They are also connected in seriesseries and are parallel to R3 6

and R4which are also connected with R3 and R4 which arein series. connected in parallel.Sample Problem R1 99 R2 9 10 Ω R3 8 Ω 99 6 Ω R5 R4 4Ω 5Ω ET= 12 V From the original circuit, you can combine R1and R2, then R3 and R4. Take note that in their connec-99 9tions, both are in series. Thus, the circuit becomes: R1 ,R2 = 18 Ω R3 = 6 Ω R4 , R5 = 9 Ω 12 VFor the combined resistance of R1and R2, R4and R5.R1,2 = R1 + R2 R3, 4 = R4 + R5 = 10 Ω + 8 Ω =5Ω +4Ω = 18 Ω =9ΩFrom the redrawn circuit above, the resistors are now connected in parallel; thus:RT = 1 1+1+ 1 =1 6 R1,2 R3 R4,5 18 =1 ( finding the lcd) = 1 x 18 16 1 + 1+ 1 RT = 3 ohms 18 6 9 =1 1 + 3+ 2 18 7

ΙΤ = ΕΤ ΡΤ = 12 V 3Ω = 4 amperes Since R1 and R2 are in series and are connected in parallel with other resistors, the same amount ofcurrent flows through them and receive a voltage supply of 12 volts.I1,2 = ET E1 = I1 x R1 R1,2 = 0.667 A x 10 Ω = 6.67 V = 12 V 18 Ω E2 = I2 x R2 = 0.667 A x 8 Ω = 0.667 A = 5.336 VI3 = ET Checking: R3 E1,2 = E1 + E2 = 6.67 + 5.336 V = 12.006 V or 12 V= 12 V E3 = I3 x R3 = 2A x 6 Ω =12 V 6Ω E4 = I4 x R4 = 1.33 A x 5Ω = 6.65 V E5 = I5 x R5 = 1.33 A x 4 Ω = 5.32 V= 2AI 4,5 = ET Checking: R 4,5 E4,5 = E4 + E5 = 6.65V + 5.32 V = 12 V = 11.97 V or 12 V 9Ω = 1.33 AChecking: IT = I1,2 + I3 + I 4,5 = 0.667 A + 2A + 1.33 A IT = 3.997 A or 4A 8

Activity 1 Study and anlyze the given circuit below and compute the following:1. RT 5. I 32. IT 6. I43. I1 7. E14. I2 8. E4 9. E2,3 R2 99 R4 R1 4Ω 8Ω 2Ω R3 96Ω 9 ET= 12 VSelf-checkDirections: Read each statement carefully. Write on on the blank if the statement is correct, and off if it iswrong. __________ 1. In a circuit with five resistors in series, current at R1 is the same as at R4. __________ 2. Total resistance in a parallel connected resistor circuit is lower than the lowest resistance value connected. __________ 3. Each resistor acts as voltage divider if they are connected in parallel. __________ 4. The current in series-parallel connected resistor divides in the parallel path and comes together in the series portion. __________ 5. A defective component in a series-connected resistor circuit disables the whole circuit. 9

Lesson 2 Capacitance in Series and Parallel Connections Generally, all capacitors store charges in their dielectrics. The ability of these capacitors to storeelectric energy is known as capacitance or capacity (c), the basic unit used is the Farad (F). Farad is a unitthat is too large for a capacitor for ordinary purposes. Usually, microfarad (uf) and picofarad (pf) are used.1F = 1,000,000 uf 1 uf = 0.000001 F1F = 1,000,000,000,000 pf or 1 pf = 0.000000000001 F1 uf = 1,000,000 pf 1 pf = 0.000001 ufSeries Capacitors There are two factors to be considered before connecting capacitors in a circuit. One is their capaci-tance value (c), and the other their working voltage or voltage rating. You can solve these, using the followingformula:Capacitance total (CT) = 1 1 + 1+ 1 C1 C2 C3Working voltage (WV) = CV1 + CV2 + CV3...Sample Problem: C1 C2 C3 2 uf/50 V 6 uf/50 V 8 uf/50 VSolution:CT = 1 =1 19 1 + 1+ 1 24 C1 C2 C3 10

=1 find the lcd = 1 x 24 19 1 + 1+ 1 CT = 1.263 uf 2 68 WV = CV1 + CV2 + CV3=1 = 50 V + 50 V + 50 V 12 + 4 + 3 24 WV = 150 voltsParallel Capacitors When capacitors are connected in parallel, their capacitance value adds, but their working voltageremains constant. Hence, the working voltage of capacitors to be connected in parallel must be equal. CT = C1 + C2 + C3...Sample Problem C1 C2 C3 4 uf / 10 V 6 uf / 10 V 5 uf / 10 VSolution: = C1 + C2 + C3 CT = 4 uf + 6 uf + 5 uf = 15 uf Working voltage should be the same for the three capacitors. Hence, working voltage in the abovecircuit is 10 V.Self-checkDirections: Match ColumnAwith Column B. Write the letter corresponding to your answer in the blank beforethe number. ColumnA Column B1. 1 uf a. 1000 F2. capacitance in parallel b. WV = CV1 + CV2 + CV33. capacitance in series c. CT = C1 + C2 + C3 11

4. working voltage in series d. 1,000,000 pf5. working voltage in parallel e. WV = CV1 = CV2 = CV3... f. CT = 1 1 + 1+1 C1 C2 C3Activity 2 Below are capacitors drawn in schematic symbols. Connect them in parallel, and compute their totalcapacitance and working voltage or voltage rating. C1 C2 C3 C4 C5 10 uf 5 uf 1 uf 100 uf 33 uf 50V 50V 50V 50V 50V Lesson 3 Inductance in Series and Parallel Connections Inductance is the property of an inductor or coil and any circuit to oppose change in current flowingthrough it when voltage is applied. Inductance is measured in terms of henry which is symbolized by letter H.Its symbol is L. Like resistors, inductors can also be connected in series, parallel and series-parallel.Inductance in Series The total inductance of coils or inductors in series is the sum of the individual inductance L values.Since the series coils have the same current, total induced voltage is a result of the total number of turns.Hence, in series,LT = L1 + L2 + L3.... This formula assumes mutual inductance between the coils. 12

L1 ]] 5 mH L2 10 mHExample 1 In the diagram above, L1 is 5 mH and L2 is 10 mH. How much is the total inductance LT?Solution: LT = L1 + L2 = 5 mH + 10 mH = 15 mH or 0.015 HNote: To convert mH to H, divide the value of mH by 1000.Series Coils with Mutual Inductance LM This case depends on the amount of mutual coupling and on whether the coils are connected series-aiding or series-opposing. Series-aiding means that the common current produces the same direction of magnetic field for thecoils. Series-opposing means, the common current produces opposite direction of magnetic field for thecoils. To calculate total inductance of two coils that are series-connected and have mutual inductance: LT = L1 + L2 + LM The LM is plus (+) when the total inductance is increasing, that is the coils are series-aiding. The LMis minus (-) when they are series-opposing, to reduce the total inductance. LM LM • •• • •• •• Series-aiding • • Series-opposing • LT= L1 + L2 - 2 LM• LT = L1 + L2 + 2 LM 13

Example (Series-aiding) Example (Series-opposing)L1 = 4 H L1 = 4 HL2 = 5 H L2 = 5 HLM = 3 H LM = 3 HFormula: LT = L1 + L2 = 2 LM Fomula: LT = L1 + L2 - 2 LM = 4 H + 5H + ( 2 x 3 H) = 4 H + 5 H - ( 2 x 3 H) =4H+5H+6H =4H+5H-6H = 15 H =3HInductance in Parallel If inductors are connected in parallel, the same principle is applied as in the case of parallel resistors,the reciprocal of the total inductance is equal to the sum of the reciprocal of the individual inductances. Thereare also three conditions to keep in mind in computing inductance in parallel. These are not mutual inductance,but are series-aiding and series-opposing. ] ]] L1 L2 L3Formula 1 ( No mutual inductance)LT= 1 1+1+1 L1 L2 L3Example:L1 = 5 HL2 = 20 HL3 = 4 HLT = ?Applying the formula: LT =1 1+1 + 1 Substituting the values of L1, L2, and L3 L1 L2 L3 14

=1 Find the LCD 1+1+ 1 5 20 4 =1 4+1 + 5 20 =1 10 20 = 1 x 20 10 = 2HFormula 2 ( With Mutual Inductance- Series-aiding)LT = 1 1 +1 L1 + LM L2 + LMExample:L1 = 5 HL2 = 2 HLM = 3 HLT = ?Applying the formula: LT = 1 1 +1 L1 + LM L2 + LM =1 1+1 5+3 2 + 3 15

=1 5 +8 40 =1 13 40 = 1 x 40 13 = 3.076 H or 3.1 HFormula 3 ( With mutual inductance - series-opposing) LT = 1 1+ 1 L1 - LM L2 - LMExample:L1 = 5 HL2 = 6 HLM = 2 HLT = ?Applying the formula: LT = 1 1 1+ L2 - LM L1 - LM =1 1 1+ 6- 2 5-2 =1 1 +1 34 16

=1 4+3 12=1 7 12= 1 x 12 7= 1.71 HActivity 3 Connect the schematic symbols of inductors below in series, and compute their total inductance inthese conditions: a. no mutual inductance b. series-aiding c. series-opposingL1 L2 L3 L4 NOTE: The inductors have mutual inductance of 4 H if they are] ] ] ]3 H 5 H 6 H 2 H in series-aiding or series-opposing.Self-check Answer the following questions:1. What do you mean by series-aiding? series-opposing?2. What will happen to the total inductance (LT) if the coils are in series-aiding?3. What will happen to the total inductance (LT) if the coils are in series-opposing?4. What will happen to the total inductance (LT) if the inductors or coils are connected in parallel? 17

Lesson 4 Transformer Ratio and Proportion The transformer is an electrical or electronic device that changes electrical power or energy from onevoltage level to another, higher or lower. It basically consists of two coils called windings electrically insulatedfrom each other and wound on a common iron core. The primary winding receives the voltage from the voltagesource and the secondary winding delivers the induced voltage. These two windings, through which voltagesand currents come in and goes out, have specific relationships with respect to voltage, current and number ofturns in the primary and secondary windings. In mathematical forms, these relationships are expressed asfollows:EP = NP IP = NS IP = ESES NS IS NP IS EPWhere: EP = primary voltage ES = secondary voltage NP = number of turns in the primary coil NS = number of turns in secondary coil IP = primary current IS = secondary currentTurns Ratio Ratio of the number of turns in the secondary to the number of turns in the primary is the turns ratioof the transformer. It is expressed in the following formula: Turns Ratio = Ns NP For instance, 1000 turns in the primary and 500 turns in the secondary provide a turns ratio of1000 / 500 or 2:1. 18