1. The internal resistance of printed circuit board testing instrument should be large
When measuring the DC voltage of integrated circuit pins, the multimeter with internal resistance greater than 20K Ω / V should be selected, otherwise it will cause larger measurement error for some pin voltages.
2. Pay attention to heat dissipation of power IC in PCB test
The heat dissipation of power IC should be good, and it is not allowed to work in high power without radiator.
3. The lead wire of PCB printed circuit board testing should be reasonable
If it is needed to replace the damaged parts of IC with peripheral components, small components should be selected. And the wiring should be reasonable to avoid unnecessary parasitic coupling. In particular, it is necessary to deal with the ground terminal between audio power amplifier integrated circuit and preamplifier circuit.
4. In printed circuit board testing, ensure the welding quality
When welding, ensure that the solder is firmly welded, and the accumulation of solder and pores are easy to cause false soldering. The welding time is generally less than 3 seconds, and the power of soldering iron is about 25W. The soldered integrated circuit should be carefully checked, and it is better to measure whether there is a short circuit between the pins with the ohmmeter. After confirming that there is no solder adhesion, turn on the power supply.
5. In printed circuit board testing, don't judge the damage of integrated circuit easily
Don't judge the damage of integrated circuit easily because most of the integrated circuits are directly coupled. Once a circuit is not normal, it may lead to multiple voltage changes, and these changes are not necessarily caused by IC damage. In addition, in some cases, when the measured voltage of each pin is or close to the normal value, it does not necessarily mean that the integrated circuit is in good condition because some soft faults will not change the DC voltage.