Multimeter repair methods and techniques Digital instruments have high sensitivity and accuracy, and their applications are almost all enterprises. However, due to the multi-factors of its failure and the randomness of encountering problems, there are not many rules to follow, and it is difficult to repair. Therefore, I will sort out some repair experience accumulated in the practical work for many years, for the reference of colleagues engaged in this profession.
1. Repair method Find the fault first, then first, then first, then first, and then hard. The methods can be roughly divided into the following types:
1. The sensory method directly judges the cause of the fault by virtue of the senses. Through visual inspection, it can find such as broken wire, unsoldering, short circuit of the bonding wire, broken fuse tube, burnt component, mechanical damage, copper foil warping on the printed circuit Starting and breaking, etc .; you can touch the temperature rise of the battery, resistor, transistor, and integrated block. You can refer to the circuit diagram to find the cause of the abnormal temperature rise. In addition, you can also check whether the components are loose, whether the pins of the integrated circuit are firmly inserted, and whether the transfer switch is stuck; you can hear and smell for abnormal sounds and odors.
2. The voltage measurement method measures whether the working voltage of each key point is normal, and can quickly find the fault point. Such as measuring the working voltage and reference voltage of the A / D converter.
3. Short-circuit method The short-circuit method is generally used in the A / D converter inspection method mentioned above. This method is often used when repairing weak and micro-electric instruments.
4. The disconnection method disconnects the suspicious part from the complete machine or unit circuit. If the fault disappears, it means that the fault is in the disconnected circuit. This method is mainly suitable for the case where there is a short circuit in the circuit.
5. Measuring component method When the fault has been reduced to a certain place or several components, it can be measured online or offline. If necessary, replace it with a good component. If the fault disappears, the component is damaged.
6. The interference method uses the human body induced voltage as the interference signal to observe the change of the liquid crystal display. It is often used to check whether the input circuit and the display part are intact.
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