Radio Design Internship Report

I. INTRODUCTION: Sometimes we think we are simple things, and when we do it, we know that it is not as simple as we imagined. But when you finish this thing, you will find that this is not as difficult as you think! ! ! Anything must be done to master certain skills, and must have certain qualities to complete. To understand a job type and master the operation techniques of welding and electronic processes, it is impossible to read books and explain. The so-called internship is to practice and operate on our own. It is necessary to truly transfer the theoretical knowledge from books to practical operations and practice. There is also the inability to operate by your own temper, must be operated under the guidance and explanation of the teacher, strictly abide by the operating procedures, and not be clever.

Second, the circuit block diagram of the amplitude-modulated medium-wave radio, the circuit diagram, and the signal flow are as follows:

For some reason, the circuit diagram is not uploaded, please forgive me! ! !

The basic working principle of the radio:
The antenna receives the electromagnetic wave signal, and after selecting the frequency through the tuner, selects the radio signal to be received. At the same time, in the radio, there is a local oscillator that generates a local oscillator signal similar to the receiving frequency. It mixes with the received signal to produce a difference frequency, which is the intermediate frequency signal. The IF signal is amplified by the intermediate frequency and then detected, and the original audio signal is obtained. After the audio signal is amplified by power, it can be sent to the speaker to sound. The high-frequency signal received by the antenna is fed into the frequency conversion tube through the input circuit and the local oscillation frequency of the radio. The frequency conversion is generated. The load frequency of the inverter stage generates a new frequency, that is, the intermediate frequency generated by the difference frequency, and the intermediate frequency only The frequency of the carrier is changed, the original audio envelope is not changed, the intermediate frequency signal can be better amplified, the intermediate frequency signal is detected and the high frequency signal is filtered out. After low-level discharge, the power is amplified and the speaker is pushed to make a sound.

Third, the preparation before installation:

Basic tools required: electric iron, iron frame, rosin, multimeter, tweezers, needle-nosed pliers, tongs, screwdriver.
Welding process requirements: 1. Carefully check the number of components before soldering, and test whether the performance of each component is good with a universal meter. 2, to clearly identify the type and role of components. 3, pay attention to the angle of the soldering iron when soldering, to make the soldering iron, solder wire and circuit board trinity, pay attention to the amount of solder wire, if more, it may affect the welding of other components is not beautiful, less may be welded Not solid. 4. When evacuating the soldering iron, make sure that the circuit board does not shake to avoid the occurrence of solder joints. It is not easy to find out the error during the subsequent debugging process. 5. When soldering the triode, pay attention to distinguish its collector, base and emitter. 6, in the overall welding to obey the post-stage installation, the principle of small and large.
Welding process training experience: In the electric welding of the radio, learning electric welding should be my biggest gain, the following briefly introduces the following welding experience, the most important thing to pay attention to is the temperature and time of welding, the soldering iron should be soldered The temperature is higher than the solder, but it should not be too high. The rosin of the soldering iron joint is just smoked. The welding time should not be too short, because the solder joint temperature is too low, the solder joints are not melted enough, and the solder joints are rough and easy to cause solder joints. The welding time is long, the solder is easy to flow, the components are overheated, easily damaged, and the printed circuit board is easily burnt or the welding short circuit occurs.
Fourth, the installation and commissioning process of the radio:
Installation: 1. First identify the components against the component list and check the quantity. Then use two 2.5x4 screws to screw the variable capacitors onto the line.
2. Install the three IF transformers and the two audio transformers on the printed circuit board with the printed circuit board diagram so that the board is separated into several pieces and then found in each block. The components that need to be installed are installed with a one-to-one number, which is not easy to make mistakes and is relatively easy. Pay attention to the polarity of the diode, the triode and the electrolytic capacitor during the installation process. Do not install the wrong one.
3. After soldering all the components, cut off the excess pins, leaving only 2-3mm from the copper foil to start soldering. Note that when soldering, there should be a small amount of solder on the soldering iron tip. The soldering iron should touch the component. The pin and the copper foil, when the solder wire is touched on the soldering iron tip, the solder wire will melt quickly, the pin of the component is connected with the copper foil, and the soldering iron is quickly separated, so that it is soldered. Welding technology is the content of the syllabus, students should carefully learn the welding technology.
4. Forming: After the board is welded, put the dial on the potentiometer and the double joint, and connect the horn, the positive piece and the spring with four wires. Insert the positive electrode and the spring into the casing. Requirements: The length of the four wires should be appropriate, especially the copper wire exposed at both ends of each wire should not be too long to prevent short circuit with other places.
5. DC measurement: There are 4 current measuring ports on the circuit board. Use the multimeter to measure the static working current of the triode at these 4 ports: ic1=0.5ma, ic2=1.5ma, ic4=3ma, Ic5.6=6ma. After the measurement is appropriate, the current port is sealed with solder, and the radio will ring. If the current is too small or too large, it is important to check whether the polarity of the second and third poles of the stage is wrong, whether the surrounding components are wrongly installed, and whether there is a short circuit in the welding.
Commissioning: 1. Frequency adjustment: Turn the tuning indicator indicator line to 530, the volume potentiometer is turned to the maximum, and the 465khz amplitude modulation signal is given by the student signal source, so that the radio is close to the signal source, and the modulated signal is received. At this time, adjust the magnetic caps of the two intermediate frequency transformers to maximize the sound. Change the frequency of the signal source to 530khz, and the magnetic cap of the red intermediate frequency transformer receives the modulation signal, then moves the position of the coil on the magnetic bar to maximize the sound, and seals the coil with wax. Turn the tuning indicator line to 1600, let the signal source output 1600khz amplitude modulation signal, adjust the trimming capacitor c1b, receive the modulation signal, and then adjust the trimmer capacitor c1a to maximize the sound, that is, the adjustment is completed.
V. Self-evaluation: I have learned a lot of valuable experience and knowledge. Through this electronic process internship, I deeply realized that the combination of theoretical knowledge and practice is a very important part of the teaching process. Only in this way can we improve our practical ability, and cultivate our independent thinking and courage to overcome difficulties. I was really happy with this internship, mainly because I personally participated in and got a radio. Although it was the first time I did my own experiments, I realized in this internship that only by doing it myself will I understand that many things are very simple. As long as you dare to do it, there is nothing you can't do. For the first time, anyone will think that the first time is the hardest.

When I just got the parts, I saw so many things, still very busy. In particular, the resistance is so small. If you lose one, it is a waste of effort. Through this electronic device internship, I not only have a greater yearning for success, but I also understand the benefits of calmness and the attitude of thinking from the perspective of failure. All the skills and experience are accumulated in practice. This time, I know a lot of circuit components and how to install them. Internship is a good opportunity to cultivate our hands-on ability. Through this process internship, we learned the basic welding technology, the detection and debugging of the radio, and the assembly process of electronic products. We also learned the identification and quality of electronic components. Inspection, knowing the assembly process of the whole machine, these are our ability to cultivate hands-on work and rigorous work style, and also lay a good foundation for our future work. In the internship, we must always keep a clear head. If something goes wrong, be sure to calmly check the analysis error! One of the most challenging exercises in my internship is my welding. Welding is one of the basic methods of metal processing. The basic operation of the "five-step method" - preparing welding, heating the weldment, melting the solder, removing the solder, removing the soldering iron - seems easy, but it takes a long time to master. However, the welding assessment forced us to complete the assessment target in just one day. It can be said that there must be a qualitative leap. So I endured my mind, arrogant and arrogant, and slowly came. In the process of constantly challenging myself, my hand holding the soldering iron does not shake, and the hand that sends the solder can basically master the dosage, and the welding technology is becoming more and more mature. When I finally managed to complete a qualified solder joint in the shortest amount of time, the fear of soldering had long since dissipated, and I was replaced by confidence in my ability to do it. In the process, I feel deeply that it may seem simple, but it may not be the case.

After the electrical and electronic internship, we learned the basic welding technology, the detection and debugging of the radio, know the assembly process of electronic products, we also learned the identification and quality inspection of electronic components, and know the assembly process of the whole machine. Our ability to cultivate hands-on work and rigorous work style have also laid a good foundation for our future work. When we first studied the "simulated electronic technology" class, we always felt that the teacher was too abstract, and through this study, it was re-established. I understand a lot of things. And this should be very useful in our future professional courses. As for our own professional, we also need to systematically study power electronics technology, automatic detection technology and signal and system knowledge, and this time we installed the radio and We used it during the debugging process. In short, in the internship, we must always keep a clear head and make mistakes. We must carefully and calmly check the analysis errors! In the end, I finally heard that my radio had successfully played a moving voice. I was really happy. I finally felt that my efforts have not been in vain!