Use waste electrical appliances to change De Sheng BCL2000 radio, APA3541 transformation
Keywords: APA3541
Be
Author: Hao Gang
Be
Deman BCL2000 radio operation is simple, easy to go; the flywheel design is very unique, fast slow-speed transmission gear adjustment card, the liquid crystal display is clear, the orange backlight is also eye-catching; the frequency modulation performance is superior, large caliber speakers use BTL power amplifier push tone Sweet, soft; medium wave sound quality is very good; use AC electricity, there is a slight exchange sound; the artificial design and mold production is very professional, close to professional high-end BCL machine; the headphone jack is no stereo, but there is stereo Line output; now the new version (knob has a red bumper) SW frequent drifting is a bit, no eradication; the quality of the band switch and the potentiometer needs to be improved, so good at the after-sales service of Demin! As for the effect of controversial SW, sensitivity and selectivity is still good, just need to listen to the time and timely correction frequency. It is also very perfect for practical functions such as switching machines. Many places where it is easier to improve and need to be tapping, and the secondary response to FM reception and headphones are used to take a better listening effect. The components needed by the machine are ingenious use, and the whole machine does not do Any changes have also added unexpected new features. 1, the machine is suitable for the power supply. Using the original AC power cord, after the FM band is turned on, you can still have a background noise and communication sound with "Shasha", and the old step-by-step high learning machine AC adapter is taken by output 9V / 1A, and will 2 7805 regulators belled on the power board in the mobile board together with the high-quality aluminum radiator, and then add the regulator circuit after disconnecting the adapter output line, and must be added to the 7805 ground foot plus 2 1N4001 diode boost Output to 6V can meet the use requirements (not necessarily 7806). The radio comes with the DC input interface and this regulator plug just cooperates. The trial comparison found that the communication sound has been basically eliminated, and the long-term continuous use of transformers is only micro-temperature, while eliminating the bed or pillow using 220V electricity directly introducing the unsafe factor brought by the radio, there is a child's family play more assured. At the same time, the original transformer is removed without reducing interference and weight. 2. APA3541 chip function This IC is a special double-channel amplifier for Taiwan Anpec high-fidelity headphones, which is widely used in all kinds of optical drives and MP3, low power consumption, distortion (THD = 0.03%), unique mute function, output impedance 32Q, 20 seconds output short circuit protection. The pin function is: 8 foot power (voltage range 3 to 8V), 2 feet have mute function, you need to pick up 100KΩ pull-up resistor to 6V power supply to output the sound signal, otherwise, 6 feet are static and eliminated Impact noise effect, the remaining pins are shown in the drawings.
Be
3. Reasons for modification and process The headphone output of the machine is a mono program. Although there is a three-dimensional lotus line output terminal, it is discovered that the sound of reluctantly hear is like a mosquito, so it needs another connection. The double-channel headphone amplifier can enjoy the true FM headset stereo. Open Samsung 52x speed CD-ROM, can find the audio output feet of 8 feet integrated circuit APA3541 in the optical drive headphone jack, and can find the audio input pin along the volume potentiometer. Other pins are also found, will apa3541 And the surrounding useful components from the optical drive (not affecting the optical drive to read normally). Another test plate is assembled. Since the original use capacitance is a high-quality mini electrolytic capacitor, it can be moved immediately, in order to reduce the volume, bias capacitor and decoupling capacitor using a patch tantalum capacitor. The enlarged plate is placed in the machine, fixed with hot melt adhesive, preventing the occurrence mechanism, directly from the VCC / 6V solder joint IC power supply can also consider the serial 10Ω decoupling anti-pressure resistance, the ground line is a bit Ground, it is not acceptable to loops. The radio double-channel headphone socket pin copper foil is cut, and the solder of the original speaker switch is shorted (note that it is not possible to ground), that is, the ear is welded to the audio output line to the radio headphone socket. The audio input line can be directly soldered on the radio line output stereo lotus terminal pin. In order not to destroy the beautiful case of the original machine, no separate volume potentiometer can be used with the headphones of the own volume line control, and when the sound of FM99.7 music, the stereo resolution is high, the sound is clear and bright. The guitar and piano music are particularly hearing. 4. Adding a full range of tuning static noise function using 2 foot static pins. The premise of achieving tuning stainless noise is that the 7 pin of the 16 foot dual-column-in-integrated circuit LA1260 is placed in the unit of the unit has the tuning indicator drive output. When the tuning radio frequency is in the optimum state, this 7 foot is loaded Negative 4V voltage, when the frequency is offset, this pin speeds into open state, no output. Therefore, the circuit shown is designed. When tuning to the radio, the three-pole saturation is turned on, the output is high to the APA3541 mute foot 2, so that the power is normal, when there is no stage, the triode base opening, C, E extreme, mute 2 The foot is on the low level, the mute is not output, thereby achieving tuning. 5. Increase the manual tuning odor-saving switch and speaker tuning static noise original stereo / mono switch for double-knife double throw, only one set of stereo state switches, and another set of unloaded copper foil leads, happens to be utilized, press The chart is picking up. In order to make the speaker output also have a tuning function, the cable AF (audio) input of the low frequency amplification (ie, the board with volume potentiometer) is cut off (each line is labeled in the root of the connector), and then from the stereo socket The intermediate two terminals can be realized by outputting the APA3541 to the two channels. At this time, the APA3541 is large as a pre-audible, and the switching function of the original two-channel socket is used to automatically cut the speaker output. Add interesting usage after modification: 1. Reasonable use of tuning static noise function is very important. When using tuning, the stereo switch is turned to the stereo position, the FM band is filtered over the two noise signals and signal weak mirror places, and the whistling noise brought by the computer is running and silent. No noise. Only some of the weaker platforms are also mute, but this non-enjoyable level is too large with headphones, and it is switched to the mono state (turn off the stainless) to listen to the remote weakening table, and close The stereo reduces noise, in line with the correct listening law and simplifies the operation. For medium waves, short-wave bands due to this unit with sensitivity gain adjustment knobs (see the instructions), you can adjust the sensitivity in the middle / short wave tuning, and use the sensitivity adjustment knob to a large location, find a ring The frequency will hear noisy background noise, then gradually rotate back to just trigger the mute operation, then carry out the normal search, form a "threshold", which will neither the weaknever is normal. Work; it is convenient to quickly adjust the radio sensitivity to the right, eliminate the background noise, especially when a short wave station is interfered, can improve the search efficiency, this method of retreating is obvious, two There is a clear boundary: If it is improving the sensitivity, it is making more disturbance, and it is best to open the "narrow-band switch" and "low pass filter switch" at this time. 2. Increase the stereo headphone output function, listening to the stereo effect. 3. Increased signalless automatic mute function, automatic stainless noise in the case of radio stop or frequency offset, protects hearing when you have a dream, do not expensity, call the station to stop broadcasting and timing (default shutdown time is 90 Minute); when you use timeline boot function, you can avoid you in a noise. 4. Manual tuning stainless switch and stereo / mono switch composite use, one-click, reasonable combination, remote reception of two incorrections 15. Added the line output / line input function. It is not used as a two-channel headphone amplifier, just switch the composite stereo to the mono, insert the source with the lotus terminal into the original line output interface. 6. The radio is used as a single-channel active speaker using the function. It is found in the power-on state. From the computer sound card and other sound sources to connect the sounding machine composite line input terminal, that is, the radio can be adjusted to adjust the volume and high and low sound. The effect of large caliber speakers. The author uses it to play CS or the sound output of the TV card is good, it feels very interesting (if you can be exchanged with the same caliber anti-magnetic speaker, you can use the display closely, otherwise, you will be 0.5m or more). It is also possible to connect the MP3 player. 7. Listen to the network broadcast function, you need to connect to the computer, the same, with the computer remote control and "tornado", listen to the software, can remotely change the station, the radio works, this way is very interesting! Note: 1. It is possible to use a 3.5mm stereo plug, socket and volume potentiometer with headphone cable to make an external tape volume adjustment, with your high-end headset, it is best to use the own volume to adjust the computer headset, cheaper. 2. Difficulty point: When the radio tuning the dual-wheel dismantage, pay attention to the one end first, then remove the wheel center screw, flat, and freely remove the tuning. 3. The first page of the specification describes this machine boot time display preset is 12 small system, which does not match the 24-hour system of the radio station frequency and the standard radio report, but there is no way to switch time formats in the instructions. The HOUR (hour) button of this machine is displayed in time (power-on does not boot), as long as you switch the time format in press 4 seconds, but if your radio cuts off the power time exceeds the memory time of the memory capacitor, the next time the time is powered. It is still displayed for 12 hours, and if you think it is a 24-hour system, it is easy to do. The reason why the process is completely solved is to remove the time display control board, and the solder of the four solder joints of the shield on the back of the circuit board first use the multi-stranded copper wire absorbing rope to absorb part solder, then heating the soldering point will Remove, you can see a soft package-specific IC in the middle of the control board. This IC has four square solder joints that are close to the upper left feet are preset jump points. After the soldering iron is hot, the label is 2 feet. The solder joint from the direction of the linket and the side grounded solder joints are directly short of the preset 24-hour jumper. Welding the shield, reinforced with a small amount of solder, prevent the motor vibration, clean the welding slag to prevent short circuits, press the reset button before power-on, then complete the settings, and keep the settings for 24 hours.
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