Pay attention to some details in printed circuit board testing, so as to ensure product quality. When testing PCB board, we should pay attention to the following 9 common sense.
1.Without isolation transformer, it is strictly forbidden to use the grounded test equipment to contact the live TV, audio, video and other equipment to test PCB board.
It is strictly forbidden to directly test TV, audio, video and other equipment without power isolation transformer with grounded enclosure. Generally, radio recorders are equipped with power transformers. But when you are about to touch special TV or audio equipment, especially those with high output power or you are not familiar with the nature of power supply, it is necessary to find out whether the chassis is charged. Otherwise, it is very easy to cause power short circuit with TV, audio and other equipment with live floor, which will affect the integrated circuit and further expand the failure.
2. Pay attention to the insulation performance of electric soldering iron in printed circuit board testing
It is not allowed to use charged soldering iron to weld. Make sure that the soldering iron is not charged. It is better to ground the shell of the soldering iron, and be more careful to MOS circuit. It is safer to use low voltage circuit of 6 ~ 8V.
3. The working principle of integrated circuit and related circuit should be known before printed circuit board testing.
Before checking and repairing the integrated circuit, it is necessary to be familiar with the function of the integrated circuit, the internal circuit, the main electrical parameters, the function of each pin, and the working principle of the circuit composed of the normal voltage and waveform of the pin and the peripheral components.
4. In printed circuit board testing, do not cause short circuit between pins
When measuring voltage or testing waveform with oscilloscope probe, do not cause short circuit between IC pins due to slide of pen or probe. It is better to measure on the peripheral printed circuit directly connected with the pin. Any transient short circuit can easily damage the IC, so be more careful when testing CMOS IC with flat package.