Method 1: Look first and measure later Use tools: multimeter, magnifying glass
When holding a circuit board of an injection molding machine to be repaired, it is a good habit to first inspect it visually, and use a magnifying glass if necessary. What do you see?
Mainly look at:
1. Whether there is a disconnection;
2. Discrete components such as resistors, electrolytic capacitors, inductors, diodes, triodes, etc. are disconnected;
3. Whether the printed circuit board connection line on the circuit board of the injection molding machine is broken or stuck;
4. Has anyone repaired it? Which components have been moved? Whether there are operational errors such as virtual soldering, missing soldering, and reverse insertion;
After confirming that the parts to be repaired do not have the above conditions, first use a multimeter to measure the resistance between the power supply and the ground of the injection molding machine circuit board. If the resistance is too small, only a few or a dozen ohms, it means that there is a If a component is broken down or partially broken down, measures must be taken to find out the broken down component.
The specific method is to supply power to the circuit board to be repaired, and touch the temperature of the components on the circuit board of the injection molding machine with your hands. The hot ones will be the key suspects. If the resistance value is normal, use a multimeter to measure discrete components such as resistors, diodes, transistors, field effect transistors, and dial switches on the board. The purpose is to first ensure that the measured components are normal. Our reason is that we can use a multimeter Solve the problem, don't complicate it.
Method 2: First outside and then inside
Tools used: circuit online maintenance instrument
If the situation permits, it is best to find a good board that is the same as the board being repaired as a reference, and then use the dual-bar VI curve scanning function to compare the good and bad of the two boards. The initial comparison point can start from the port , and then from the surface to the inside, especially the comparative test of capacitance, can make up for the shortcoming that the multimeter is difficult to measure whether there is leakage online.
Method 3: First easy and then difficult
Tools used: circuit online maintenance instrument, electric soldering iron, marker pen
In order to improve the test effect, before the online functional test of the circuit board of the injection molding machine, some technical processing should be done on the repaired board to minimize the negative impact of various interferences on the test process. The specific measures are:
1. Preparation before the test
Short-circuit the crystal oscillator, and solder a leg of the large electrolytic capacitor to make it open, because the charging and discharging of the capacitor can also cause interference.
2. Use the exclusion method to test the device
During the online test or comparison of the devices, please directly confirm the test results for the devices that pass the test (or are relatively normal) for recording; if the test fails (or is relatively out of tolerance), you can test it again. If you pass, you can also confirm the test results first, and continue testing like this until the devices on the board are tested (or compared), and then go back to deal with those devices that failed the test (or are relatively out of tolerance).
For devices that fail the functional online test, the instrument also provides an unconventional but more practical treatment method. Since the power supply of the instrument to the circuit board of the injection molding machine can be applied to the corresponding power supply and ground pin of the device through the test clip, if Cut the power pin of the device with a blade, and the device will be separated from the power supply system of the circuit board of the injection molding machine. At this time, the online functional test of the device will be carried out. The effect is equivalent to "quasi-offline", and the accuracy rate will be greatly improved.
3. Use the ASA-VI curve scan test to compare and test the devices that have not been covered by the test library
Because the 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 there is a reference board, through the comparison test, the device also has a strong fault detection ability. This function makes up for the deficiency that the online function test of the device is subject to the test library, and expands the detection range of the instrument for the circuit board failure of the injection molding machine.
In reality, it often happens that a good board cannot be found as a reference, and the circuit structure of the board to be repaired does not have any symmetry. In this case, the ASA-VI curve scanning comparison test function does not work, and the online function test Due to the incomplete component test library, it is impossible to test every component on the circuit board of the injection molding machine, and the circuit board of the injection molding machine is still unable to be repaired. This is the limitation of the circuit online maintenance instrument, just like there is no cure for all diseases. .
Method 4: Be quiet before moving
Since the circuit online maintenance instrument can only perform functional online testing and static feature analysis on the components on the circuit board of the injection molding machine at present, whether it is completely repaired or not must be tested by the whole machine. Therefore, it is best to check whether the power supply of the equipment is Correctly supply to the circuit board of the injection molding machine as required.
