When doing PCB circuit board inspection, in order to ensure the quality of the product, what problems must be paid attention to? Next, please come to understand with the editor;
1. It is strictly forbidden to use the equipment whose casing has been grounded to directly test the PCB board of TV, audio, video and other equipment without power isolation transformer.
When you come into contact with a TV or audio equipment with a large output power or do not know the nature of the power supply, it is necessary to find out whether the chassis of the equipment is charged, otherwise it will easily cause a short circuit of the power supply, which will affect the integrated circuit and cause further expansion of the fault.
2. Pay attention to the insulation performance of the electric soldering iron when testing the PCB board
It is not allowed to use a soldering iron to weld with electricity. Make sure that the soldering iron is not charged. It is best to ground the shell of the soldering iron.
3. Understand the working principle of integrated circuits and related circuits before testing
It is necessary to be familiar with the function of the integrated circuit used, the internal circuit, the main electrical parameters, the function of each pin, the normal voltage of the pin, the waveform and the working principle of the circuit composed of peripheral components.
4. Be careful not to cause a short circuit between pins
When measuring voltage or using an oscilloscope probe to test the waveform, it is best to measure on the peripheral printed circuit that is directly connected to the pin. Any instantaneous short circuit will easily damage the integrated circuit.
5. The internal resistance of the test instrument should be large
When measuring the DC voltage of the pins of the integrated circuit, a multimeter with an internal resistance greater than 20KQ/V should be selecte.
6. Pay attention to the heat dissipation of power integrated circuits
Power integrated circuits are not allowed to work under high power conditions without radiators.
7. The leads of the PCB board should be reasonable
The wiring should be reasonable to avoid unnecessary parasitic coupling, especially the ground terminal between the audio power amplifier integrated circuit and the preamplifier circuit.
8. To ensure the welding quality
The integrated circuit that has been soldered should be carefully checked. It is best to use an ohmmeter to measure whether there is a short circuit between the pins, and then turn on the power after confirming that there is no solder adhesion.
9. Don't easily conclude that the integrated circuit is damaged
Because the vast majority of integrated circuits are directly coupled, once a certain circuit is abnormal, it may cause multiple voltage changes, and these changes are not necessarily caused by damage to the integrated circuit.
