（1） Psychological preparation
1. The rigorous scientific attitude of a qualified repairman.
2.Strong resistance to pressure.
4. Love the industry, have study, collect the spirit.
1. Digital multimeter, mechanical multimeter each piece.
3.Electric bridge (non-essential).
4. Actively collect information on various mainstream models.
6. Screwdriver pliers solder iron solder and so on.
7.Three power sources
（3）Preparation of professional knowledge (minimum threshold)
1. Be familiar with the reading method of resistance capacitors and other commonly used components.
2. Familiar with basic electricity, mold and electric knowledge.
3. Understand the working principle of commonly used power change lines (half-bridge, full bridge, single end, etc.)
4. Familiar with measurement methods of various components.
（一） Initial failure machine
1. Ask about the main failure condition of the machine, such as not clear the fault of the transmission.
2. Determine whether the line of this machine belongs to its familiar brand
1. Listen to the burglary after starting the inspection, check for obvious burning, fracture, and hard mechanical problems.
2. According to the main description of the malfunction, the most suspicious degree is first checked.
3. After completing the first two points, the diagnostic procedures will be arranged in chronological order.
1. Determine whether the fault problem occurs in the main circuit or auxiliary circuit.
2. If the main circuit should be checked carefully, the damaged components can be replaced, and the electricity can be sent.
3. If the problem is in the auxiliary circuit, the main circuit and the auxiliary circuit should be cut off to prevent damage to the main circuit during maintenance.(single and auxiliary)
4. The hybrid failure, such as the breakdown of power device, is not guaranteed by normal driving. At this time, the order of repair should be understood, first controlled and later.
（4） Main circuit maintenance detection procedure
1. The power conversion process of ordinary inverter welder is generally in the process of rectification - inverter - secondary rectifier.
2. The normal phenomenon of the rectifying part is that the transmission power cannot (trip), the dc bus voltage of the power device is not normal and the voltage is not normal, and the machine is not responding.
3. The general phenomenon of inverter is relatively easy to find from appearance.
4. The secondary rectifying parts are relatively single and easy to measure, and most of them can be measured directly from the output terminals to observe whether there is a short circuit, open circuit, or abnormal pressure drop.
（5）Control circuit maintenance diagnosis process
Note the separation of channels, common MOS digital multimeter transistors can reach threshold voltage, IGBT, can use the mechanical watch to use the finger as a conductor, form a simulation drive, to detect its good or bad.