The detection of the main board of the forklift truck is the process of finding, determining and correcting the fault of each electronic component on a main circuit board. The whole testing process is a thinking process and a testing process that provides logical reasoning clues. The electrical system of the forklift is composed of thousands of components. During maintenance and repair, if you directly test and check its main circuit one by one It would be very time-consuming to find the problem with every component in the board, and it would be very difficult to repair. So from the fault phenomenon of the forklift to the cause of the fault, the check-in maintenance method is an important testing process. The testing engineer must gradually accumulate maintenance experience in the maintenance, testing, and maintenance process of the circuit board. rather than rhetoric. After the circuit board of the forklift truck is repaired, you can refer to the following methods for basic inspection. It should be noted that anti-static gloves should be worn before testing, because everyone has static electricity all the time. When testing the circuit board of the forklift truck, the maintenance personnel often feel that the fault is not found, but the more the test is, the worse the repair is. until it cannot be repaired. In fact, when you test, the static electricity on your body has passed the test point to the relatively weak microprocessor and memory circuits, causing permanent damage. If you have anti-static gloves, wear one end on your hand and connect the other end At the grounding end of the forklift circuit main board, such accidents can be effectively prevented.
1. Detect with a multimeter
1. Take the digital meter as an example: For example, if a circuit board is not powered on, when the circuit board is powered off, first turn the multimeter to the corresponding resistance gear to check whether the insurance is normal, the resistance +5V, and the GND resistance. is too small (under 50 euros), etc.
2. If the above measurement is normal, then turn the multimeter to the diode gear to check whether the diode is damaged. First, connect the red test lead to the positive electrode of the diode, and the black test lead to the negative electrode of the diode. At this time, the normal diode should display 0.5mⅤ~0.7mV, which is normal, otherwise It is a bad tube, four diodes are measured by analogy.
3. If the above measurements are normal, then measure the voltage on the circuit, turn the multimeter to the corresponding DC voltage range, connect the black test lead to the circuit board ground, and the red test lead to the measured point, for example: measure the voltage after rectification and filtering and many more.
4. Use a multimeter to perform a simple test on suspicious components such as resistance, capacitance, inductance, etc. within the range, and test whether the resistance value increases, the capacitance short circuit, open circuit and capacitance value change, inductance short circuit and open circuit and other phenomena.
Second, the detection method of the short circuit fault of the public power supply of the main board of the forklift circuit
In the inspection and maintenance of the main circuit board of the forklift truck, if there is a short circuit of the public power supply, it is often a big problem, because many devices share the same power supply, and each device using this power supply is suspected of being short-circuited. If there are not many components on the board, Using the method of "hoeing the earth" can eventually find the short-circuit point. If there are too many components, it will depend on luck whether the "hoeing the earth" can hoe the situation. A more effective method is recommended here. Using this method, you can get twice the result with half the effort, and you can often find the fault point quickly. Adjust the open circuit voltage to the power supply voltage level of the device, first adjust the current to the minimum, and add this voltage to the power supply voltage point of the circuit, such as the 5V and 0V terminals of the 74 series chip, depending on the degree of short circuit, gradually increase the current, use When you touch the device by hand, when you touch a device with obvious heat, this is often a damaged component, which can be removed for further measurement and confirmation. Of course, the voltage must not exceed the working voltage of the device during operation, and it cannot be reversed, otherwise other good devices will be burned.
3. Basic inspection
1. Observation method: First, observe whether there is any obvious component damage on the circuit board of the forklift truck, such as the burning and bulging of electrolytic capacitors, the burning of resistors, and the burning of power devices. Check the welding of the main board of the forklift truck, such as whether the printed circuit board is deformed and warped; whether there are solder joints falling off or obvious soldering; whether the copper cladding of the circuit board is warped, burnt and blackened.
2. Power-on inspection: If it is clear that the board has been damaged, the original voltage can be slightly increased by 0.5-1V, and the IC on the board can be washed by hand after the power is turned on, so that the faulty chip will heat up, so as to sense it.
3. Logic pen inspection: Check the input, output, and control poles of the key suspects for the presence or absence of signals, strength, etc.
4. According to the instructions of the manual, first check whether there is a signal (wave pattern) at the input and output terminals of the suspected chip. If there is no input or output, then check whether there is a signal (clock) of the control line of the IC. This IC is very likely to be bad, and there is no control signal. Trace to its previous pole until the damaged IC is found.