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Learning Objectives: After studying this chapter, you should be able to:
• describes the process of making a three transistor radio;
• make a three transistor radio.

Material in thi...


Learning Objectives: After studying this chapter, you should be able to:
• describes the process of making a three transistor radio;
• make a three transistor radio.

Material in this Chapter:
A. Preparation of Tools and Materials
B. Chassis / PCB manufacturing
C. Installation of components on the chassis
D. Wiring Components at Terminals
E. Soldering
F. Trial Transistor Radio Experiments


Before making a three transistor radio, we need to get to know the tools and materials needed for making the radio. The tools and materials needed for the manufacture of a three transistor radio are as follows.

The tools needed in the manufacture of a three transistor radio include:
a. screwdriver,
g. zinc scissors,
b. hacksaw,
h. vise (vise),
c. hammer,
i. solder bout,
d. drill,
j. multitester (AVO),
e. miser,
k. testpen, and
f. pliers,
1. oscilloscope (if any).

Materials The schematic and materials or components required for the manufacture of a three transistor radio are as shown in Figure 2.1 below.

three transistor radio schematic

List of components:
R1 = 470K resistance
R2 = 52K resistance
R3 = 400K resistance
R4 = 3K resistance
Rs = 100K resistance
R6 = resistance 2K9
R7 = 220K resistance
R8 resistance 39K
TR2 = TR2 = transistor 0071 or the like
TR3 = transistor 0072 or the like
F = ferrite rod
L1 = L2 = antenna spool
K = DA79 crystal diode
C2 = C3 = 0.01 RF capacitor
C4 - C7 = capacitor 10 1.A.F

Chapter 2 Making Radio Three Transistors 13


Chassis is a PCB (Printed Circuit Board) which functions to put all the circuit components that will be practiced.
For practice, it is best to design and manufacture your PCB. There are three ways to make PCBs, namely the simple or direct way, the afdruk method, and the screen printing method.
The simple or direct way of making PCB is the process of making PCBs by directly drawing a plan or laying out on the copper surface.
Afdruk PCB manufacturing is PCB manufacturing through the afdruk process using the positive 20. PCB layout is drawn on tracing paper, wax paper, or thick plastic. Then the layout that has been drawn is transferred through the afdruk process to the copper surface by spraying a positive liquid 20. In this case the layout can be made quickly and in the desired quantity. Furthermore, the copper is dissolved like a PCB process in a simple way. Consider the PCB manufacturing process below.

PCB Manufacturing in a Simple Way
a. Tools and Materials
1. Non-metal place (container), for example a plastic bucket.
2. Non-metal stirrers, for example wood.
3. Hammer and nails.
4. Small drill 1 mm size.
5. Copper slabs (plain tinsel board).
6. Tracing paper, wax paper, or thick plastic.
7. Finishes such as waterproof markers, paints and varnishes.
8. Ferric chloride (FeC13) solution.
9. Hot water.
10. Rub ash and soap.
11. Cleaners, eg thinner, methylated spirits and alcohol.

b. Simple PCB Manufacturing Process
1 Prepare the electronic circuit schematic that will be made like the simple adapter schematic in Figure 2.2 next to it.

simple adapter scheme

2. Draw a plan or layout on tracing paper, wax paper, or thick plastic. Determine the point of each component, then connect the component legs according to the schematic drawing. Consider the example layout of Figure 2.3. Lay out size must match the desired size.

pcb layout

3. Transfer the layout to the copper (PCB) component by redrawing it using a waterproof marker or permanent marker eg artine 70 markers. Layouts can also be made onto PCB plates with carbon.
4. Cover or layer the PCB layout with marker, paint, or varnish. Try not to line jagged and not in contact with other lines that should not be connected. Next, dry the PCB that is already covered or coated.
5. Place a period with a hammer and nails in the place of the component legs.
6. Insert the dry plain copper plate into the ferric chloride solution. A ferric chloride solution can be made by dissolving 3 tablespoons of ferric chloride in 0.5 liters of hot water in a non-metallic container such as a plastic bucket. Stir the copper plate (PCB) with wood or another non-metallic stirrer, until any layers that are not covered with the marker, paint, or varnish are dissolved. Do it for 15 to 30 minutes.
7. Remove the copper plate (plain tinak board) from the solution, then dry with fresh water.
8. Dry and clean the finish (marker, paint, or varnish) with thinner, sprite, alcohol, or other cleaner.
9. Punch the points where the component legs are using a 1 mm drill bit.
10. Clean the finished PCB with rubbing ash mixed with soap to make it shiny. Wrap the PCB in plastic when not using it immediately.
Before the copper plate is dissolved, the plan drawing on the plate can be added with the name of the maker, the name of the series, the class, and the attendance number. This is useful so that PCBs are not confused with those of other students.
The speed at which copper dissolves in the ferric chloride solution is determined by four factors, namely: whether the solution is concentrated, the temperature of the solution, stirring, and the thickness of the copper layer.
To understand the PCB manufacturing process with a simple process, consider the chart in Figure 2.4 below.

chart of the pcb manufacturing process in a simple way

There are two ways to design the layout of the components, namely:
• according to the schematic drawing;
• by grouping similar components.

The layout of the first component does not change the layout of the circuit components. So, the components are placed in the same way as the components in the circuit schematic. Meanwhile, the second method by grouping similar components looks neater. For example, resistors, transistors, and ceramics are placed in one group each.

PCB Making by Afdruk Way
a. Tools and Materials
1. Mat and materials in the PCB manufacturing process in a simple way.
2. Positive liquid 20 as an ingredient.
3. Sodium Hydroxide (NaOH) solution as a means of generating images.

b. PCB Manufacturing Process with Liquid
1. Draw / lay out / schematic to be practiced onto tracing paper or wax paper.
2. Take the tinak board (PCB) according to the size of the layout. Clean the copper layer from the dirt.
3. In a dark place or not exposed to sunlight / lights, place the plain PCB horizontally or horizontally on the surface of the copper layer. Next, from a distance of 1 to 20 cm, spray the positive 20 evenly and thinly onto the surface of the copper layer.
4. Dry the sprayed tan in a dark place. Drying with a temperature of 28 degrees Celsius takes 24 hours and at a temperature of 70 ° C takes 15 minutes. Keep in mind, drying with temperatures above 70 ° C can damage the afdruk layer. If it will be used immediately, drying can use a fan.
5. Still in a dark place, stick and glue the plan drawing (lay out) with insulation on the surface of the copper layer.
6. Shine directly with the sun or a lamp with a power of about 2 x 100 watts for 2 to 3 minutes. If the positive layer 20 is a bit thick, the irradiation is carried out for 4 to 5 minutes. Timing precisely is influenced by the strength of the light. To get good results, it needs to be done more than once.
7. Take the pertinak and plan drawing to the dark room, remove it, and dip the Tinak into the sodium hydroxide solution obtained by dissolving 7 grams of NaOH in 1 liter of water. This dyeing process takes 2 minutes and on the surface of the copper layer an image plan will appear. If the reappeared plan image is missing, it means that the irradiation has been carried out for too long. Conversely, if the immersion time has exceeded 2 minutes and the image of the plan has not appeared, there will be less illumination. If these things happen, the manufacturing process must be repeated from scratch.
8. Once in a bright place, dissolve the tinam with a good plan image into the fern chloride solution until the copper layer outside the path is completely dissolved (the part that is not exposed to light because it is covered by the plan drawing ink will all dissolve). For this reason, it is necessary to remember that when designing a plan drawing, what is in bold with ink is not the path but is off the track.
9. If the copper coating outside the PCB path has dissolved, remove and clean with acetone or ketone solutions purchased at a chemical drugstore.
10. Do the drilling in the places where the components will be installed. To avoid oxidation (rusting), PCBs that are not immediately used can be stored in plastic.

To make it easier to understand the PCB manufacturing process by means of afdruk, it can be seen in Figure 2.5.

chart of pcb manufacturing process by afdruk way

Before installing, the components on the PCB must be tested first. This aims to find out whether the components are still good or damaged. Installation of components needs to pay attention to the following sequence.
1. Passive components: resistors, non-polar capacitors, electrolytic capacitors, IT transformers and OT transformers.
2. Active components: transistors and diodes.
3. Complementary components: varco, ferrite antenna, potentiometer, antenna spool, power cable, and loudspeaker cable.

Wiring components is tightening the connecting cables between the components and the PCB. The steps taken are as follows.
1. Connect the dots marked LS by cable to the plug located on the aluminum chassis.
2. Connect by means of a point wire marked with S to the switch terminal located on the aluminum chassis.
3. Connect the red wire for positive polarity and the black wire for negative polarity to the plug on the back of the aluminum chassis provided that this plug is for the current source (battery).
4. Connect R2 (potentiometer) to the potentiometer terminal located on the aluminum chassis. R2 function is to adjust the strength of the sound on the radio.

To get a good soldering result, it is necessary to know the basics of soldering. A good soldering process will produce a solder that is small, dull, and shiny.

The three transistor radio experiment steps are as follows.
1. Check the work that you have finished with the supervisor before trying it.
2. After getting permission from the supervisor, try this three transistor radio. To get broadcast, we have to shift (tuning) the variable capacitor using a beng.

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