6 repair analysis methods for multimeters
Repair essentials
When looking for obstacles, we should first look at the outside and then the inside, first the easy and then the difficult, break them into parts, and focus on breakthroughs. The essentials can be roughly divided into the following categories:
1. Feel the Dharma
Rely on the senses to directly determine the cause of the failure. Through superficial inspection, it can be found that such as broken wires, desoldering, short circuits, broken fuse tubes, burned components, mechanical damage, lifted and broken copper foil on printed circuits. etc.; you can touch the temperature rise of batteries, resistors, transistors, and integrated blocks, and refer to the circuit diagram to find out the cause of the abnormal temperature rise. In addition, you can also use your hands to check whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the transfer switch is stuck; you can hear and smell whether there are any strange sounds and smells.
2. Voltage measurement method
Measuring whether the working voltage of each key point is normal can quickly identify 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 above-mentioned inspection methods of A/D converters. This method is often used when repairing weak current and micro-electrical instruments.
4.Circuit breaking method
Isolate the suspicious part from the whole machine or unit circuit. If the fault disappears, it means that the fault is in the disconnected circuit. This method is mainly suitable for situations where there is a short circuit in the circuit.
5.Measurement of components
When the failure has been reduced to one location or several components, it can be measured online or offline. If necessary, replace it with good components. If the fault disappears, it means that the component is bad.
6. Nuisance law
Using the voltage induced by the human body as an interference signal to observe the changes in the LCD display is often used to check whether the input circuit and the display part are complete.
