1. Percussion hand pressure method

We often encounter the phenomenon of good and bad when the instrument is running. Most of this phenomenon is caused by poor contact or weak welding. For this situation, percussion and hand pressure can be used.

The so-called "knock" is to tap the plug-in board or component lightly with a small rubber buckle or other knocking objects to see if it will cause an error or shutdown failure. The so-called "hand pressure" is a failure. When it appears, turn off the power and re-press the inserted parts, plugs and sockets with your hands, and then turn it on to try whether the fault will be eliminated. If you find that it is normal to tap the case, and then it is not normal, *prefer all connectors first Re-insertion and try again, if the trouble is unsuccessful, I have to find another way.

2. Observation method

Using the sense of sight, smell, and touch, sometimes, damaged components will change color, blisters or burn spots, burnt components will produce some special smells, short-circuited chips will be hot, and it can be observed with the naked eye. Go to the place where the soldering or de-soldering is.

3. Elimination

The so-called elimination method is to determine the cause of the fault by unplugging some plug-in boards and devices in the machine. When a plug-in board or device is removed and the instrument returns to normal, it means that the fault has occurred.

4. Replacement method

It is required to have two instruments of the same model or have enough spare parts. Replace a good spare part with the same component on the faulty machine to see if the fault is eliminated.

5. Contrast method

Two instruments of the same model are required, and one of them is in normal operation. In this method, you must have necessary equipment, such as multimeters, oscilloscopes, etc. According to the nature of comparison, there are voltage comparison, waveform comparison, and static impedance. Comparison, output result comparison, current comparison, etc.

The specific method is: let the faulty instrument and the normal instrument run under the same conditions, and then detect the signals at some points and compare the two sets of signals measured. If there are differences, you can conclude that the fault is here. This method requires maintenance The personnel have considerable knowledge and skills.

6. Heating and cooling method

Sometimes, the instrument will work for a long time, or when the working environment temperature is high in summer, it will malfunction. Turn off and check it is normal, stop for a while and turn it on again. It will malfunction after a while. This phenomenon is due to individual ICs or components. The performance is poor and the high temperature characteristic parameters fail to meet the index requirements. In order to find out the cause of the failure, the temperature rise and fall method can be used.

The so-called cooling is to wipe the anhydrous alcohol with cotton fiber on the parts that may fail to cool down and observe whether the failure is eliminated. The so-called temperature rise is to artificially increase the ambient temperature, such as using an electric soldering iron. Near the suspicious point (note that the temperature must not rise too high to damage the normal components) and try to see if the fault occurs.

7. Shoulder riding

The shoulder-riding method is also called the parallel method. A good IC chip is mounted on the chip to be inspected, or a good component (resistance capacitor, diode, triode, etc.) is connected in parallel with the component to be inspected to maintain good contact. If the fault is caused by an open circuit or poor contact inside the device, this method can be used to eliminate it.

8. Capacitor bypass method

When a certain circuit produces a strange phenomenon, such as a display disorder, you can use the capacitor bypass method to determine the part of the circuit that is probably faulty. Connect the capacitor across the power and ground of the IC, and connect the transistor circuit across the base input Observe the effect on the fault phenomenon at the output terminal or collector output terminal. If the capacitor bypass input terminal is invalid and the fault phenomenon disappears when bypassing its output terminal, it is determined that the fault is in this superior circuit.

9. State adjustment method

Generally speaking, before the fault is determined, do not touch the components in the circuit casually, especially the adjustable devices, such as potentiometers, etc., but if you take the reference measures in advance (for example, do it before touching Good position mark or measured voltage value or resistance value, etc.), it is still allowed to be touched if necessary, and the fault may be eliminated after the change.

10. Isolation method

The fault isolation method does not require the same type of equipment or spare parts for comparison, and is safe and reliable. According to the fault detection flow chart, the fault search range is gradually narrowed by dividing and encircling, and then with signal comparison, component exchange and other methods, the fault will generally be found quickly Where.