LED-skærmen har fire hoveddele: computerkontroldel, skærmdrevmatrix, led-display-array og strømforsyning. Blandt dem er der flere problemer:
1. Interface problem. Phenomenon: The computer information cannot be displayed, check the cable
2. Power supply problem. The LED display uses a low-voltage and high-current power supply, which is not much different from an ordinary DC power supply
3. Drive problems. If there is no display in each row or column, it is the corresponding drive circuit (chip) problem, just replace it
4. Display problems. Long-term use of the LED display screen may be damaged and aging, just repair and replace it.
LED display common fault handling process-diagnosis process:
1. Determine whether your display is a synchronous display or an asynchronous display; the display of the synchronous display depends on the setting of the display, and the asynchronous display does not depend on the setting of the display;
2, determine whether your display is a partial display problem or the entire screen has a problem;
Partial display abnormality can eliminate communication problems. Generally, it can be determined that the display hardware is malfunctioning. You should contact us immediately to prevent the malfunction from expanding;
There are many possible reasons for the abnormal display of the whole screen:
For the synchronous display, you should confirm whether the setting of the display is changed, whether the communication is normal, whether the transmission is normal, and then whether the reception is normal;
For asynchronous display screens, first confirm whether the parameters of the display screen: hardware address, width, height, IP are changed, if these parameters are correct, then test whether the communication is normal, and finally confirm whether the display control is normal or the interface of the display unit board.
The display screen is composed of display unit boards one by one, and the signal is transmitted through a flat cable.
instruction:
GND = ground (GND) L = latch (LAT or ST) S = clock (Clk) OE = enable (/OE)
R=red data G=green data U=blue data ABCD=line signal H=decoded line signal N=floating V=VCC) transformation
In order to save customers' investment, we can provide customers with services such as renovation and renewal of their existing LED displays. According to the situation of the customer's display screen, it can be roughly divided into the following three types:
1. Same display unit board interface
Many manufacturers' display unit board interfaces are not standard. If the customer's display unit board interface is the same as the interface mentioned above, we can upgrade the system, such as text screen video screen, low gray scale video screen, and high gray scale video screen. This method has low cost, The effect is quick.
2. Display unit board interface
If the customer display unit board interface is not exactly the same as the standard interface listed above, but the number and type of signals are the same, this type of display can also be upgraded, and the cost is slightly higher than the first case.
3. Completely different display unit board interface
The customer's original display unit board interface is not exactly the same as the one mentioned above. In this case, the cost of the transformation is relatively large. Except for the LED module and some ICs, all other parts, such as PCB boards and Ito systems, have to be replaced, which is costly.
1. Repair of display unit board The display unit board does not light up. Reason: There may be no power supply, the 74HC245 input interface is broken, and the E signal is short-circuited to a high level. One line of the display unit board is always on. Cause: The decoder, 74HC245, 74HC138 are broken. One row of the display unit board does not light up. Reason: 4953, 74HC38 is broken or the connection between the pin and the power tube is disconnected. One column of the display unit board does not light up. Reason: A pin of the driver IC or resistor is soldered or the circuit is disconnected. One row or column of the module does not light up. Cause: The LED module pins are soldered. 2. Synchronous video system Turning on the computer, the display screen has no response. Reason: The communication line is faulty (such as bad connection). Turn on the computer, the display screen flickers, but there is no signal. Reason: The driver software LEDSETUP is not started. The screen is displayed normally, but the full screen is flickering. Cause: The communication line, the sending card and the receiving card or the receiving card are faulty. The color of the display is abnormal. Cause: There is a problem with the display mode setting. Part of the display is abnormal. Reason: Check the corresponding scanning board. There may be no power supply or poor contact. 3. Asynchronous text screen system There is no display when booting. Cause: The main control board may have no power or the voltage is too low. The old content is displayed when booting, but the communication fails. Reason: The communication line is abnormal, the wiring is incorrect, the communication interface chip 232 is broken, or the computer communication interface is broken. The content is lost. Reason: The 3.6V battery is out of power. The above are common faults, and customers can usually solve them by themselves. If there is a more complicated situation, please contact us, we will respond at any time and provide you with the best quality service. Understanding of common signals of LED display CLK clock signal: The shift pulse provided to the shift register, each pulse will cause the data to be shifted in or out of one bit. The data on the data port must be coordinated with the clock signal to transmit data normally, and the frequency of the data signal must be 1/2 times the frequency of the clock signal. In any case, when the clock signal is abnormal, it will make the whole board display disorderly. STB latch signal: Send the data in the shift register to the latch, and display the data content through the drive circuit to light up the LED. But because the drive circuit is controlled by the EN enable signal, the prerequisite for its lighting must be that the enable is turned on. The latch signal also needs to be coordinated with the clock signal to display a complete image. In any case, when there is an abnormality in the latched signal, the entire board will be displayed in a disorderly manner. EN enable signal: the entire screen brightness control signal, also used for screen blanking. Just adjust its duty cycle to control the change of brightness. When the enable signal is abnormal, the entire screen will appear dark, dark, or tailing. Data signal: Provide the data needed to display the image. It must be coordinated with the clock signal to transmit the data to any display point. Generally, the red, green and blue data signals are separated in the display screen. If a data signal is short-circuited to the positive or negative pole , the corresponding color will appear fully bright or not bright. When the data signal is suspended, the corresponding color display is uncertain. ABCD linjesignal: Det eksisterer kun under dynamisk scanningsvisning. ABCD er faktisk et binært tal, og A er den laveste bit. Hvis ABCD-signalet udtrykkes i binært, er det maksimale kontrolområde 16 linjer (1111), og kun AB-signal er nødvendigt i 1/4-scanning. , Fordi AB-signalområdet er 4 linjer (11). Når linjestyringssignalet er unormalt, vil der være fænomener som visningsforskydning, fremhævning eller billedoverlapning. Common troubleshooting methods (tools: multimeter, soldering iron, blade, screwdriver, tweezers... etc.) When judging problems, they must be dealt with in a primary and secondary manner. Obvious and serious ones should be dealt with first, and minor problems should be dealt with afterwards. Short circuit should be the highest priority. 1. Modstandsdetekteringsmetode, juster multimeteret til modstandsområdet, detekter modstandsværdien af et bestemt punkt på et normalt printkort, og detekter derefter det samme punkt på et andet samme printkort for at teste, om modstandsværdien er forskellig fra den normale modstand. Hvis de er forskellige, så er det bekræftet. The scope of the question. 2. Voltage detection method, adjust the multimeter to the voltage range, detect the voltage to the ground at 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. Kort-detektionsmetode. Indstil multimeteret til kort-detektionsgearet (nogle er diodespændingsfaldsgear eller modstandsgear, normalt med alarmfunktion), og detekter, om der er et kortslutningsfænomen-. Hvis der findes en kortslutning, skal den først løses for at forhindre, at den brænder Andre enheder. This method must be operated when the circuit is powered off to avoid damage to the meter. 4. Spændingsfaldsdetekteringsmetode, juster multimeteret til diodespændingsfaldsdetektionsudstyret, fordi alle IC'er er sammensat af mange grundlæggende enkeltkomponenter, men er miniaturiseret, så når der er en strøm, der passerer gennem en pin af det, vil der være en spændingsfald over stiften. 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. 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. (Smart Test Card) 3. Check whether 74HC245 is short-circuited with a solder joint, and whether the corresponding enable (EN) signal input and output pins on the 245 are soldered or short-circuited to other circuits. LED display Note: Mainly check the power supply and enable (EN) signal. B. When scanning the dots obliquely, the regular interlaced lines are not bright and the screen overlaps 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, and D output terminals corresponding to 245 are open, soldered, or short-circuited between the output terminals 138. 2. 3. Check whether the signals A, B, C, and D are short-circuited or a signal is short-circuited to the ground. Note: Mainly detect ABCD line signals. C. One or several lines are not bright when it is all on 1. Check whether the circuit between 138 and 4953 is open, soldered, or short-circuited. D. During line scanning, two or several lines (usually a multiple of 2, regular) are lit at the same time 1. Check whether the signals of A, B, C, and D are short-circuited. 2. Check whether the 4953 output terminal is short-circuited with other output terminals. E. Single point or multiple points (irregularly) do not light up when all on 1. Find the corresponding control pin of the module and measure whether it is short-circuited with this line. 2. Replace the module or single lamp. F. One or more columns are not bright when all on 1. Find the pin that controls the column on the module, and test whether it is connected to the output terminal of the driver IC (74HC595/MBI5124,,,). G. There is a single point or a single column highlight, or the entire line is highlighted, and it is not controlled 1. Check whether the column is short-circuited with the power ground. 2, check whether the line is short-circuited with the positive pole of the power supply. 3. Replace its driver IC. H. The display is chaotic, but the signal output to the next board is normal 1. Detect whether the STB latch output terminal corresponding to 245 is connected to the latch terminal of the drive IC or the signal is short-circuited to other lines. I. The display is chaotic and the output is abnormal 1. Check whether the STB signal latched by the clock CLK is short-circuited. 2. Check whether the clock CLK of 245 has input and output. 3. Check whether the clock signal is short-circuited to other lines. Note: Mainly detect clock and latch signals. J. Display lack of color 1. Check whether there is input and output at the data terminal of the color of 245. 2. Check whether the data signal of the color is short-circuited to other circuits. 3. Check whether the cascaded data ports between the driver ICs of the color are open, shorted, or soldered. Note: The voltage detection method can be used to find the problem more easily, check whether the voltage of the data port is different from the normal one, and determine the fault area. K. Problem with output 1. Check whether the line from the output interface to the signal output IC is connected or short-circuited. 2. Check whether the clock latch signal of the output port is normal. 3. Check whether the cascade output data port between the last drive IC is connected to the data port of the output interface or whether it is short-circuited. 4. Whether the output signals are short-circuited with each other or short-circuited to the ground. 5. Check whether the output cable is in good condition. A. The whole screen is not bright (black screen) 1. Check whether the power supply is energized. 2. Check whether the communication line is connected and whether it is connected incorrectly. (Sync screen) 3. The synchronization screen detects whether the green light of the sending card and the receiving card is flickering; if there is no flicker, check whether the card is inserted properly, 4. Whether the green light of the receiving card communication flickers, if there is no flicker, check whether the network cable is loose, if not, whether the crystal head is pressed well 5. Whether the computer monitor is protected, or the display area of the screen is black or pure blue. (Sync screen) B. The whole unit board does not light up (black screen) 1. If several consecutive boards do not light up in the horizontal direction, check whether the cable connection between the normal unit board and the abnormal unit board is connected; or whether the chip 245 is normal, 2, the longitudinal direction of several consecutive boards is not bright, check whether the power supply of this column is normal. C. The unit board does not light up 1. Check whether the line pin and 4953 output pin are connected. 2, check whether 138 is normal. 3. Check whether 4953 is hot or burnt. 4. Check whether 4953 has a high level. 5. Check whether the control pins 138 and 4953 are connected. D. The unit board lacks color 1. Check whether the 245 R.G data is output. 2. Check whether the output pin of the normal drive IC and the input pin of the abnormal drive IC are connected. Boot: (1) Turn on the display first, and then turn on the host computer. s (2) Start the LED control panel, enter the display editing software, open the edited file, and run the program list. (3) Turn on the dedicated switch for the display to supply power to the display. Shut down: (1) Turn off the dedicated switch for the display first. (2) Exit the dedicated editing software for the display screen and exit all programs. (3) Turn off the host computer and turn off the display. (4) Turn off all power supplies connected to the display device. Precautions: (1) The operation of the display screen must be carried out strictly in accordance with the sequence of power on and off. (2) When the display is running, please do not plug or unplug the system board and all the devices connected to the display when the power is on. (3) It is not allowed to play games and install software that is not related to the display on the computer dedicated to the display screen, so as to prevent viruses from invading the computer, so as not to affect the normal operation of the display screen.
