November 29, 2021

Experience of making power amplifier with TDA1553CQ

A batch of disassembled power amplifier integrated blocks were mail-ordered for electronic production. In order to check the quality of the blocks, a circuit with a socket was first made and the power amplifier blocks were tested one by one. Install the TDA1553co. After inputting the signal, the current of the whole machine is greater than 2.5A, the amplifier block is overheated, and the sound is distorted. There is serious low-frequency self-excited sound in the speaker, but the signal sound from the speaker of channel 1 is distorted, but it is better than the sound. Road 2 is much larger.

When changing all TDA1553CQ (a total of 30), there is no good one. If you do n’t connect the signal and interfere with each input terminal by hand, the “beep” interference noise can be transmitted from the speaker. In the experiment, the input signal of channel 2 was accidentally disconnected, and the channel 1 speaker immediately transmitted A loud singing sound, working current is less than 300.mA; channel 2 alone, fault reproduction. The result of changing a TDA1553CQ is still the same. Is it because the coupling capacitance of channel 2 is bad? After removing the quantity, there is actually a leakage resistance of 50kΩ (500 meter, R & TImes; 10kQ file). Because it is a new polypropylene capacitor and it is used in low-voltage occasions, it is estimated that there is no problem. , Without measurement, just go to the machine, change a good capacitor, and troubleshoot. Since the current of the whole machine is less than 500mA at high volume, it is necessary to develop a good habit of measuring before the device is put on the machine.

The signal source is taken from the headphone jack of the CD player. There is no output coupling capacitor. The internal resistance of the signal source is very small. Due to the leakage of the input capacitance of the power amplifier, the input resistance of the TDA1553CQ is greatly reduced, resulting in low-frequency self-excitation. According to the actual measurement, when + 12V power is supplied, the DC potential at both ends of the speaker is zero under normal conditions; when self-excited, there is actually a 5v potential difference across the speaker.

Some experiments have succeeded in putting the blocks into the TDA series. When testing the DC voltage at the input, it is easy to cause low-frequency self-excitation, the current of the whole machine increases greatly, the power amplifier is overheated, the power amplifier with a perfect protection circuit will turn off the output, and the power amplifier block will continue if there is no protection function Overheating, it is easy to fry the block, there are some power amplifier blocks, the measurement time is too long and it is easy to burn the horn. Such as TDA1517 (gain 20dB) and TDA1553CQ / Q (26dB), you can only use the gear above 50V (500 meter) to measure the voltage at the input terminal; while TDA1519A (40dB) and TDA1557Q (46dB) can only use the range above 250V measuring.

For the power amplifier block, generally use a multimeter to measure the resistance to judge whether it is good or bad. Use a multimeter to measure the positive and reverse resistances of the power supply to ground, power supply to output, and output to ground (if necessary, input to power, input to output, and input to ground), and the two channels are symmetrical (For BTL power amplifiers, the two outputs of each channel should be absolutely symmetrical to the resistance of the other ends, otherwise, the output will produce severe distortion), the power amplifier block is generally good. The author used this method to judge more than 100 power amplifier blocks, and basically did not misjudge.

The power supply voltage range of TDA1553Q / co is + 6V ~ + 18V, 14.4V is recommended. When RL = 4Q, the power supply is 14.4V, the distortion THD = 10%, the output is 22WX2, the gain is 26dB, and the (12) foot is connected to the ground with a 4.7μF capacitor At the time, the start-up anti-shock delay is 0.5s, the performance parameter of TDA1557Q, the application circuit is the same as TDA1553Q / CQ. However, the coupling capacitor is 270uF and the gain is 46dB. If the (12) pin is not connected to a capacitor, two 1N4148 are connected in series and the negative electrode is grounded to improve low-frequency distortion, but the sound quality difference between the two connections cannot be heard.

Experience of making power amplifier with TDA1553CQ

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