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Jun 17,2021| LED Knowledge
How to deal with the failure of the led electronic display? This is one of the issues that customers care about. Dead pixels are the most common problem of LED display. It means that the LED cannot work normally and there are black spots. Other common faults include the whole screen does not light up, part of the screen does not light up, the whole screen is blurred, part of the screen is blurred, the screen is flashing, etc. Follow the LED display manufacturers to learn more about the maintenance plan when the LED display fails!
One, short circuit treatment
1. Resistance detection method, adjust the multimeter to the resistance mode, detect the resistance value of a certain point of a normal circuit board, and then detect the same point of another same circuit board to test whether the resistance value is different from the normal resistance. If they are different, the scope of the problem is determined.
2. Voltage detection method, adjust the multimeter to the voltage range, detect the ground voltage of a certain point of the suspected circuit, and compare whether it is similar to the normal value, otherwise the scope of the problem is determined.
3. Short-circuit detection method. Set the multimeter to the short-circuit detection gear (some are diode voltage drop gears or resistance gears, usually with alarm function) to detect whether there is a short-circuit phenomenon. If a short-circuit is found, it should be solved first to prevent it from burning Other devices. This method must be operated when the circuit is powered off to avoid damage to the meter.
4. Voltage drop detection method, adjust the multimeter to the diode voltage drop detection gear, because all ICs are composed of many basic single components, but are miniaturized, so when there is a current passing through a pin of it, There will be a voltage drop across the pin.
Generally, the voltage drop on the same pin of the same type of IC is similar. According to the voltage drop value on the pin, it is necessary to operate with the circuit power off. This method has certain limitations. For example, if the tested device is high-impedance, it cannot be detected.
Two. Unit board failure
A. The whole board is not bright
1. Check whether the power supply is connected to the signal line.
2. Check whether the test card recognizes the interface. If the red light of the test card flashes, there is no recognition. Check whether the light board and the test card have the same power ground, or the light board interface has a signal and ground short circuit, which makes the interface unrecognizable.
3. Check whether the 74HC245 has a short-circuit with a solder joint, and whether the corresponding enable (EN) signal input and output pin on the 245 is solder-beared or short-circuited to other circuits. Note: Mainly check the power supply and enable (EN) signal.
B. When the dots are scanned obliquely, the regular interlaced lines are not bright and the screen is overlapped.
1. Check whether there is any disconnection, virtual welding, or short circuit between the A, B, C, and D signal input ports to 245.
2, check whether the A, B, C, D output terminals corresponding to 245 are open, soldered, or short-circuited between the A, B, C, D output terminals and 138.
3. Check whether the signals of A, B, C, D are short-circuited or a signal is short-circuited to ground.
Note: Mainly detect ABCD line signals.