The common methods for repairing instruments are:
1. Intuitive method Visually identify faults by hand, eyes, ears, and nose. Such as: broken wire, cold welding, component touch, poor plug-in contact, components overheating, sparking smoke, there is a coke paste, mechanical transmission parts lack of oil wear, clearance is too large or rolling, abnormal noise and so on.
2. Circuit parameter measurement method Use ten thousand meters to measure the voltage, current, and resistance values ​​of each point in the circuit and compare it with the normal value to determine the fault location. If necessary, the fault can be compared with the new complete machine.
3. Replacement method Replaces the work of suspect parts, plug-ins, and normal parts with the same purpose. The purpose is to narrow down the scope of fault finding. Faulty components can be found during replacement.
4. Test equipment inspection method Use special test equipment to test the whole machine or components of the instrument, which can effectively detect the defects and improve the quality of repairs.
5. The cutting method removes doubtful circuits from the whole unit or unit circuit, and gradually narrows down the fault search range. If the working current is too large or there is a short-circuit fault, a part of the circuit can be disconnected from the whole machine, and the current change can be seen to judge this. Some circuits are normal.
6. Signal tracing method According to the instrument to be repaired, select different signal generator output signals, or human interference and step signal input instrument, and observe the signal transmission status in the circuit, such as voltage or waveform, to judge the fault.
7. Waveform Method Use an oscilloscope to observe the waveforms of the instrument's circuits and components and compare it with the normal waveform to determine if the power is working properly.
8. Short circuit method For disturbances, self-excitation, and other faults, a short circuit at a certain point in the circuit can be performed. The fault disappears after a short circuit, indicating that the fault is before the short-circuit point, and vice versa after the short-circuit point. If there is a difference in the DC potential between the two points that are to be short-circuited, they should be short-circuited by a suitable capacitor.
There are several simple ways to determine instrument failures:
1. The meter does not show anything, mainly because the battery is not properly powered or is not in good contact.
2. Megger high voltage indicator light but no resistance test. Check if there is a high voltage output, if the test line is disconnected, and if the test article is in good contact.
3. When the ground resistance meter test shows "1" or "1 and OPEN", the range is not properly selected or the ground pole to be tested is open and the current assist pole is too large.
4. FC-2G is normal. Turn the "representation" of the meter's rear panel to the "Current" bit, short the panel test hole with a wire, and hit "0.75U" in the "Auto" position. Turn on the high voltage and the display shows 1000μA ± 2 FC. If not, then the FC -2G is faulty.