To repair a relatively unfamiliar injection molding machine circuit board without any schematic diagrams, so-called "experience" in the past is difficult to achieve. Although people with deep hardware knowledge are confident in repairs, if method is improper, they can still get twice result with half effort. So, what can be done to improve maintenance efficiency? Based on experience of long-term injection molding machine maintenance, it is concluded that following steps should be followed in an orderly manner.

 

Use tools: multimeter, magnifying glass. When holding a circuit board of an injection molding machine to be repaired, a good habit is to visually inspect it first, use a magnifying glass when necessary. What should you look at?. Mainly see:
1. Whether there is disconnection;
2. Discrete components such as resistors, electrolytic capacitors, inductors, diodes, triodes, etc. are disconnected;
3. Whether printed circuit board connection line on circuit board of injection molding machine is broken or stuck;
4. Has anyone repaired it? What components have been moved? Whether there are operational errors such as false soldering, missing soldering, and reverse insertion; After confirming that repaired part does not have above conditions, first use a multimeter to measure resistance between power supply and ground of circuit board of injection molding machine. If resistance is too small, only a few or a dozen ohms, it means that there are components on circuit board of injection molding machine that have been broken down or partly broken down, measures must be taken to find out broken down components. Specific method is to supply power to repaired circuit board and touch temperature of components on circuit board of injection molding machine by hand. Hot ones will be key suspects. If resistance value is normal, use a multimeter to measure discrete components such as resistance, diodes, transistors, field effect transistors, and dial switches on board. Purpose is to first ensure that measured components are normal. Our reason is that if you can solve a problem with a multimeter, you should not complicate it.　

Use tool: If situation permits, it is best to find a good board that is same as repaired board as a reference, then use dual-rod VI curve scanning function to compare good and bad of two boards. Initial comparison point can start from port, then from table to inside, especially comparison test of capacitance, which can make up for shortcoming of multimeter that it is difficult to detect whether leakage is online.　

Use tools: circuit online repairer, electric soldering iron, marker pen. In order to improve test effect, before online function test of injection molding machine circuit board, some technical treatment should be done on repaired board to minimize negative impact of various interferences on test process. Specific measures are:

1. Preparation before test. Short-circuit crystal oscillator, solder a pin to make it open for large electrolytic capacitors, because charging and discharging of capacitors can also cause interference.

2. Use exclusion method to test device. During online test or comparison of device, if device passes test (or relatively normal), please directly confirm test result for record; If test fails (or is relatively out of tolerance), you can test it again. If it still fails, you can also confirm test result first, continue test until device on board is tested (or compared), then go back and deal with those devices that have not passed test (or are out of tolerance).
For devices that have not passed functional online test, instrument also provides a less formal but more practical processing method, because power supply of instrument to circuit board of injection molding machine can be applied to corresponding power supply and ground pin of device through test clip. If power supply pin of device is cut, device will be separated from power supply system of injection molding machine circuit board. At this time, online function test of device will be carried out. Since other components on injection molding machine circuit board will no longer interfere, actual test effect is equivalent to "quasi-offline", and accuracy rate will be greatly improved.

 

3. Use ASA-VI curve scan test to compare and test devices not covered by test library. Because ASA-VI intelligent curve scan technology can be applied to comparison test of any device, as long as test clip can clamp device, and a reference board, through comparison test, it also has a strong fault detection capability for device. This function makes up for insufficiency of device's online function test subject to test library, expands instrument's detection range of injection molding machine circuit board failures.
In reality, there are often scenarios where a good board cannot be found for reference, circuit structure of board to be repaired does not have any symmetry. In this case, ASA-VI curve scan comparison test function does not work, online function test cannot be completed due to incomplete device test library. It is impossible to test every component on circuit board of injection molding machine. Circuit board of injection molding machine still cannot be repaired. This is limitation of circuit online repairer, just like there is no cure for all diseases. .　　

Since circuit online repairer can only perform functional online testing and static characteristic analysis of components on injection molding machine circuit board at present, whether it is completely repaired must be tested by whole machine. Therefore, it is best to check whether power supply of equipment is correctly supplied to circuit board of injection molding machine during inspection.