In terms of probability, various electrical faults with good and bad times include the following situations:
1. Poor contact
Poor contact between the board and the slot, when the cable is broken internally, it will not work, the plug and the wiring terminal are not in contact, and the components are soldered.
2. The signal is interfered
For digital circuits, faults will only appear under certain conditions. It is possible that too much interference has affected the control system and caused errors. There are also changes in individual component parameters or overall performance parameters of the circuit board, which makes anti-interference The ability tends to the critical point, which leads to failure;
3. Poor thermal stability of components
From a large number of maintenance practices, the thermal stability of electrolytic capacitors is the first to be poor, followed by other capacitors, triodes, diodes, ICs, resistors, etc.;
4. Moisture and dust on the circuit board.
Moisture and dust will conduct electricity and have a resistance effect, and the resistance value will change during the process of thermal expansion and contraction. This resistance value will have a parallel effect with other components. When this effect is strong, it will change the circuit parameters and cause malfunctions. occur;
5. Software is also one of the considerations
Many parameters in the circuit are adjusted by software. The margins of some parameters are adjusted too low and are in the critical range. When the operating conditions of the machine conform to the reason for the failure determined by the software, an alarm will appear.