Nine precautions for overhauling instruments

Nine precautions for overhauling instruments:
1. When using a multimeter with an ohmic stop, remember not to carry out live measurement.

2. When using a logic pen or oscilloscope to detect signals, pay attention not to make the probe contact the two measurement pins at the same time, because the essence of this situation is to form a short circuit under power up.

3. When detecting the filter capacitor in the power supply, the positive and negative electrodes of the electrolytic capacitor should be short-circuited first, and do not use test leads instead of wires to discharge the capacitor during the short-circuit, as this will easily burn the core wire. You can take a 220V, 60 ~ 100W lamp with a lamp lead, connected to both ends of the capacitor, and the bulb will flash at the moment of discharge.

4. When troubleshooting the instrument in a humid environment, it is necessary to use a multimeter to measure the smoothness of each point of the printed circuit, because the main fault in this case is corrosion of copper foil.

5. When the internal circuit of the instrument is overhauled, if the contacts of the mounting components and the circuit board are coated with insulating varnish, when measuring the parameters of each point, a common hand stitch can be welded to the tester of the multimeter so that the points can be directly measured through the paint layer, No need to peel the paint over a large area.

6. Do not plug or unplug all kinds of control boards and plugs with power on. Because in the power-on situation, plugging and unplugging the control board will generate a strong induced electromotive force. At this moment, the counterattack voltage is very high, and it is easy to damage the corresponding control board and plug.

7. Don't knock blindly and randomly during maintenance, so as not to expand the fault, the worse the repair.

8. When disassembling and adjusting the instrument, the original position should be recorded for recovery.

9. When repairing precision instruments, if you accidentally flew small parts, you should first determine the place where it may fall off. Do not look for it in the east and turn it in the west. You can use magnet scanning and line-of-sight scanning to find it.

In short, in the maintenance of instruments and meters, the basic principles of instruments and meters should be understood first, and the knowledge and skills related to electronics should be mastered, and all instrumentation manuals, drawings and other technical information should be prepared, and a kind of Good working quality, so as to improve efficiency and reduce errors in the maintenance of instruments and meters.