The computer circuit board of the embroidery machine sh […]
The computer circuit board of the embroidery machine should be repaired on a relatively unfamiliar circuit board without any schematic diagram. The so-called "experience" in the past is difficult to do, although people with deep hardware skills are full of confidence in maintenance, but if the method is improper It’s more than half the work. So, what can we do to improve maintenance? According to the statistics of my years of maintenance experience, the following steps should be followed and carried out in an orderly manner.
Method 1: First outside and inside
Use tools: circuit online repair instrument
If the situation permits, it is best to find a good board with the same board as the reference, and then use the double-bar VI curve scanning function to perform good and bad comparison test on the two boards. The starting comparison point can start from the port. Then, from the comparison between the table and the inside, especially the capacitance test, it can make up for the shortcoming that the multimeter is difficult to measure whether it is leaking.
Method 2: First easy and difficult
Use tools: circuit online maintenance instrument, electric iron, marker
In order to improve the test results, before the online functional test of the board, the technical processing of the repaired board should be done to minimize the negative impact of various interferences on the test process. The specific measures are:
1. Preparation before testing the embroidery machine circuit board
The crystal is short-circuited, and a large electrolytic capacitor is soldered to make it open, because the charge and discharge of the capacitor can also cause interference.
2. Using the exclusion method to test the device
During the online test or comparison process of the device, if the test passes (or is relatively normal), please confirm the test result directly for recording; if the test fails (or is relatively poor), you can test it again, if still Pass, you can also confirm the test results, and then continue testing until the devices on the board are tested (or compared), and then go back to the devices that failed the test (or more out of tolerance). For devices that do not pass the functional online test, the instrument also provides a less formal but more practical processing method. Since the instrument supplies power to the board, it can be applied to the corresponding power and ground of the device through the test clip. The power supply foot is edge-cut, then the device will be disconnected from the circuit board power supply system, and then the device will be tested for online function. Since other devices on the circuit board will not interfere again, the actual test result is equivalent to "quasi-offline". "The precision rate will be greatly improved."
3. Compare and test the devices not covered by the test library with the ASA-VI curve scan test.
Because ASA-VI intelligent curve scanning technology can be applied to the comparison test of any device, as long as the test clip can clamp the device, and then there is a reference plate, through the comparison test, the device also has strong fault detection capability. This function makes up for the shortcomings of the online functional test of the device subject to the test library, and expands the scope of detection of the board fault. In reality, there is often a situation in which a good board cannot be found for reference, and the circuit structure of the board itself is not symmetrical. In this case, the ASA-VI curve scan comparison test function does not work, and the online function test Due to the incompleteness of the device test library, it is impossible to complete the test of each device on the circuit board, and the circuit board still cannot be repaired. This is the limitation of the circuit online maintenance instrument, just like the medicine without cure.
Method 3: First, then move
Since the circuit online maintenance instrument can only perform on-line test and static characteristic analysis on the device on the circuit board, whether it is completely repaired or not must pass the whole machine test and inspection. Therefore, it is best to check whether the power supply of the device is required according to the requirements. Correct supply to the board
After confirming that the above conditions are not repaired, first measure the resistance between the power supply of the board and the ground with a multimeter. Usually, the resistance of the board is 70-80? Above, if the resistance value is too small, only a few or a dozen ohms, indicating that components on the circuit board are broken down or partially broken down, it is necessary to take measures to find out the components that are broken down. The specific method is to supply power to the repaired board, and touch the temperature of each device on the circuit board by hand. The hot hand will be the key object of doubt. If the resistance is normal, use a multimeter to measure the components on the board such as resistors, diodes, triodes, FETs, and disconnectors. The purpose is to ensure that the measured components are normal. Our reason is that Don't complicate the problem solved by the multimeter.