Fault classification and maintenance methods of automated communication equipment

During the operation of automated communication equipment, various faults may occur, affecting the operation of the system, and sometimes even causing destructive consequences. In order to find out the fault in a timely and accurate manner and eliminate it, we must have some understanding of the fault classification and maintenance of communication equipment.

1 Classification of faults

1.1 According to the nature of the fault, it can be divided into soft fault and hard fault

Soft faults refer to faults caused by software system errors. Common soft faults include program errors, virus damage, operating errors, setting errors and blind operations.

Hard failure refers to physical damage to the equipment hardware: one is caused by human and environmental reasons, such as harsh environment, poor power supply, static damage or violation of operating procedures; the other is caused by electrical components, such as damage to components, contact plug-ins, printed circuits, etc.

1.2 According to the scope and degree of fault impact, faults can be divided into global, related, local, and independent faults.

Global failure refers to a failure that affects the normal operation of the entire system; correlation failure refers to a failure that has a causal or correlation relationship with other failures; local failure refers to a failure that only affects certain items or functions of the system; independent failure refers to a failure that occurs in a specific component. For example, if the power fuse blows and the device cannot start, it is a global failure, and the cause may be a short circuit of a related component, that is, the correlation of the failure. Local and independent failures are generally unified.

1.3 According to the time and period of the fault, it can be divided into fixed fault and temporary fault.

A fixed fault refers to a fault phenomenon that is stable and can occur repeatedly. Its main causes are open circuit, short circuit, damage to mechanical parts or failure of a component. A temporary fault refers to a fault that lasts for a short time, has an unstable working state, and is sometimes good and sometimes bad. Its cause may be caused by decreased component performance or poor contact.

2. Sequence of maintenance process

2.1 Analyze and think first, then start maintenance

There may be many reasons for the failure, and the phenomenon and time of the failure may be uncertain. When a failure is found, the possible causes should be analyzed first, and the relevant scope should be listed, and the technical data of the relevant scope should be found as a theoretical guide. "Do it now" may not be suitable for equipment maintenance, that is, it is important to follow the procedures and order.

2.2 Outside first, then inside

It is wrong to open the case rashly at any time. Only after eliminating external equipment and connection failures and then proceeding to internal maintenance can unnecessary disassembly be avoided.

2.3 Mechanical part first, then electronic part

The integrity of the mechanical components should be checked first, followed by the electronic circuit structure and the mechatronic integration.

2.4 First static, then dynamic

That is, first repair with the power off, and then connect the power. There is a principle issue here, that is, safety.

3. Maintenance methods

3.1 Direct Observation

Direct observation includes two situations: no power connection and power connection. First, observe without power connection, and use human sensory organs (eyes, ears, hands, nose) to check whether the relevant plug-ins are loose, have poor contact, have cold solder joints or loose solder joints, have broken wires, have short circuits, have components corroded, have zoomed, have discolored, have power supply short circuits, have overcurrent, have overvoltage, have blown fuses, etc. After carefully observing that all components inside and outside the machine are correct, connect the power supply to observe whether there is any smoke, sparks, or abnormal sounds inside the machine. If there is any, shut down the machine immediately, and gently tap the chassis and components to see if there is any poor contact. At the same time, touch the suspected components with your hands to see if there is any overheating, and make corresponding judgments based on the degree of overheating and temperature of the components.

3.2 Measurement method

This method is relatively simple and direct. It can generally determine the location of the fault based on the fault phenomenon. With the help of some measuring tools, it can further determine the cause of the fault and help analyze and solve the fault.

Common measurement and inspection methods include voltage inspection, resistance inspection and current inspection. The voltage inspection method is to determine the fault by measuring the working voltage of the component and comparing it with the normal value; the resistance inspection method is a method of measuring the resistance value of the component to the ground or itself to determine the fault. It is effective in repairing open circuit, short circuit faults and determining faulty components; the current inspection method is to connect the ammeter in series into the circuit to measure the working current. This method is very inconvenient to repair and is rarely used.

3.3 Plug-in method

A method of finding faults by "inserting" or "pulling" a plug-in. Although this method is simple, it is a commonly used and effective method that can quickly find the cause of the fault. The specific steps are:

3.3.1 First open the connection between the faulty device and all connected devices, then close the power switch of the faulty device. If the fault disappears, check whether the connected devices and connecting wires have short circuits (such as touching wires, short circuits, pins touching, etc.). If so, eliminate them; if not, check the faulty device itself.

3.3.2 Unplug all the plug-in boards of the faulty equipment. If the fault disappears, the fault is on a plug-in board. If the fault still occurs, check the power supply of the equipment carefully to see if there is any fault.

3.3.3 Carefully check each plug-in board to see if there is any collision or short circuit. If so, eliminate them. If not, plug them in one by one, turn the computer on and off to test. This way, you can quickly find which plug-in board is faulty.

3.3.4 Find the faulty plug-in board, and then determine which integrated block or electronic component is damaged based on the fault phenomenon and nature.

3.4 Heuristics

The trial method is a method of replacing a suspected faulty plug-in board or component with a normal plug-in board or good component (large-scale integrated circuit) to test the fault. This method is often used in debugging and maintenance, especially when it is not clear where the fault is. This method is more convenient and direct. However, if the fault is very serious, there is a burn-in phenomenon, and the object cannot be clearly identified, this method can be used, because the faulty plug-in board may be destructive, and random replacement may cause the new plug-in board to be damaged again.

3.5 Other maintenance methods

3.5.1 The isolation method, also known as the segmentation method, is to separate the components for local inspection to determine the location of the fault.

3.5.2 The comparison method is to find the cause of the fault by comparing the correct characteristics with the incorrect characteristics.

3.5.3 The temperature increase method is to artificially increase the ambient temperature or the temperature of local components (using a hair dryer can increase the ambient temperature of local components, but be careful not to increase the temperature too high, so as not to burn out normally working components), accelerate the "death" of some components with poor high temperature parameters, and help find faults. Sometimes the equipment will fail after working for a long time or the ambient temperature rises, but it is normal when it is shut down for inspection, and the failure will recur after working for a period of time. At this time, the "temperature increase method" can be used to check.

3.6 Comprehensive approach

The comprehensive method is to consider the above methods together to deal with the fault. In this way, when dealing with some more complex faults, the cause of the fault can be found and eliminated in a timely and accurate manner.

4 Conclusion

Determining faults must be based on good technical knowledge, so that problems can be discovered and solved accurately and in a timely manner. In addition, when looking for faults, try to broaden your thinking, think of all factors that may cause the fault, and carefully analyze and eliminate them.