The LED display unit board, also known as the LED display module or unit for short, is the main constituent unit of the LED display, which is composed of LED light emitting diodes and driving circuits, driving ICs and plastic kits.
In the LED display industry, LED unit boards are now divided into two categories. The indoor unit board industry is generally called surface mount (three-in-one surface mount); outdoor and semi-outdoor are generally called modules. The characteristics of indoor surface mount: high image sharpness, rich colors and shortcomings due to high price; outdoor and semi-outdoor module unit board features: high brightness, waterproof, rich colors, and lack of technical guidance for installation
An important part of the LED electronic display is the LED unit board. If there is a problem with the unit board, it will directly affect the overall quality of the LED display! Therefore, how to distinguish the quality of the LED unit board is a concern of LED display vendors. The following Led exhibition summarizes some common methods for testing LED unit boards.
LED unit board plate. Some LED unit board manufacturers use cheap flame-retardant paper boards or single-sided fiber boards as PCB circuit boards for LED lights in order to compete at low prices. Because all glass fiber PCB boards are expensive. At first, no difference can be seen. Generally, within one year, it will be broken due to moisture, UV damage, oxidation and other reasons, resulting in the entire LED unit board being scrapped. High-quality LED unit boards must use double-sided all-glass fiber PCB boards. Although the cost is high, the quality is guaranteed.
IC device. Observe whether the brand of the IC device used is consistent. What type of IC is used, and how many ICs are used, these are enough to affect the quality of the LED unit board. Some LED display manufacturers, in order to save costs, will deliberately reduce the number of ICs or mix other brands of ICs when producing unit boards.
Lamp beads and chips. The naked eye cannot tell the quality of the lamp beads. Can only rely on a long test, which is the aging test that experts say. The general LED display manufacturer's approach is: power on before leaving the factory, and check whether the LED display can operate normally, it will not go through a long aging test. Because there are time costs and labor costs.
Check whether there are any missing or misplaced components on the chip, and whether there is a short circuit on the component pin burrs. Check whether the solder joints of the straight inserts are smooth and round, and whether the board surface is clean and tidy, and there is no missing welding. Check the insertion flatness of the luminous dot matrix and the consistency of the ink color.
Power-on test (refer to the steps in the "Performance Test Report"): ① Power-on test for consistency of the light-emitting dot matrix; ② Power-on test to effectively protect the line drive tube CEM4953;
The above is a common method for detecting the quality of LED unit boards. I hope it will be helpful for LED display merchants. In addition, quality is king, and rejecting cheap and shoddy LED displays is also what manufacturers need to do to avoid damage to the unit board and affect normal work and subsequent unnecessary maintenance.
The problems of the Led unit board are mainly divided into four points:
1 . The entire board is not flashing: It is mainly because the unit board is not connected to the power supply or the wiring in the board is incorrectly connected.
2 . The board is not flashing, and the function transmission is normal: This is caused by the built-in damage to the circuit board. You can short circuit the 4th and 5th pins of the 74HC138.
3. Not flashing every other third: Damage to 4953 inside the board.
4. Interlaced flashing: can be analyzed to be a circuit problem.
①: Check if the 74HC245 and 74HC138 built in the unit board are soldered.
②: Use a multimeter to measure whether the 74HC138 * pin voltage is around 2.5V, if necessary, replace the 74HC138
③: Measure the power transmission status of the ICA signal with the gold needle.
Source: HC LED Screen Network