This paper lists the processing methods of various problems of LED display, including short circuit processing, unit board fault processing, outdoor (module) troubleshooting, whole screen troubleshooting, control system troubleshooting, driving part problem processing and so on. More detailed, it is worth collecting.
Judge the problem must first after the way of the treatment, will be obvious, serious first processing, small problems after processing.(Short circuit shall be of the highest priority)
1. Short circuit processing
1, resistance detection method, the multimeter to the resistance file, detect a normal circuit board at a point to the ground resistance value, and then detect the same circuit board of the same point test and the normal resistance value is different, if different to determine the scope of the problem.
2. Voltage detection method, adjust the multimeter to the voltage file, detect the voltage to a certain point of the suspected problem circuit, and compare whether it is similar to the normal value, otherwise the scope of the problem is determined.
3, short circuit detection method, the multimeter to the short circuit detection block (some diode pressure drop or resistance file, generally has the alarm function), detect whether there is a short circuit phenomenon, found short circuit should be the priority to solve, so that it does not burn other components. The method must be operated in the case of the circuit power failure to avoid damage to the table.
4, pressure drop detection method, the multimeter is adjusted to the diode pressure drop detection file, because all IC are composed of many basic units, just miniaturized, so when there is a current through the pin, there will be a voltage drop on the pin. Generally, the pressure drop on the same IC of the same model is similar. According to the comparison of the pressure drop value on the pin, it must be operated in the case of circuit power failure. The method has some limitations, such as the detected device is highly resistant, it can not be detected.
2. 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 is used to identify the interface, the test card red light flashing is not recognized, check whether the light board is the same power source as the test card, or the signal of the light board interface is short circuit to the ground, and the interface cannot be recognized.(Intelligent test card)
3. Check whether 74HC245 has a short welding circuit, and whether the corresponding enabling (EN) signal input and output foot on 245 is short welded or short circuit to other lines. Note: Mainly check the power supply and enable (EN) signal.
B. In the dot oblique scan, the regular intervals are not highlighted and the screen overlap
1. Check whether there is A broken line or false welding or short circuit between A, B, C, D signal input port and 245.
2. Check whether the output terminals of A, B, C, D corresponding to 245 and 138.
3. Check whether the short circuit between A, B, C, D signals or A signal short circuit to the ground. Note: The ABCD line signals are mainly detected.
C. One line or several lines are not bright
Check the line between 138 and 4953 for open circuit, false welding and short circuit.
D. In line scanning, two or several lines (usually a multiple of 2, regular) are lit at the same time
1. Check the short circuit between signals A, B, C and D.
2. Check whether the output terminal of 4953 is short circuit to other output terminals.
E. Single or multipoint (irregular) without brightness
1. Find whether the corresponding control pin of the module is short circuit to the bank.
2. Change the module or the single light.
F. One or several columns are not bright
Find the pin controlling the column on the module and measure whether it is associated with the driver IC (74HC595 / TB62726......) Output end connection.
G. Have a single point or single column highlight, or a full line highlight, and is not controlled
1. Check whether the column is short-circuit to the power supply.
2. Check whether the line is short circuit to the positive electrode of the power supply.
3. Replace the driver IC.
H. shows confusion, but the signal output to the next plate is normal
Check whether the corresponding STB latch output of 245 is connected to the latch terminal of the driving IC or the signal is short-circuit to other lines.
I. Disconfusion and abnormal output
1. Check whether the clock CLK latch STB signal is short circuit.
2. Check whether the clock CLK of 245 has input and output.
3. Check whether the clock signal is short-circuit to other lines. Note: Main detect clock and latch signals.
J. Shows the lack of color
1. Check the input and output of the data side of 245.
2. Check whether the data signal of this color is short-circuit to other lines.
3. Check whether the cascade data port between the driver IC of this color has open circuit or short circuit or false welding.
(Note: the voltage detection method can be used to find the problem, test whether the voltage of the data port is different from the normal, and determine the fault area.）
K. There is a problem with the output
1. Check whether the line of output interface to signal output IC is connected or short circuit.
2. Check whether the clock latch signal of the output port is normal.
3. Check whether the cascade output data port between the last driver IC is connected to the data port of the output interface or has a short circuit.
4, whether the output signal is short circuit to each other or short circuit to the ground.
5. Check whether the output line is good.
L. Unit board appears 8 points or 16 points row, column or single point is not bright, long bright, dark bright
1. Whether the module pin and lead corresponding to the fault have short circuit, false welding and open circuit.
2. Whether the common connection line between the upper and lower and left and right modules of each cell (cell board) is normal (connect the multimeter to the ring end, the lead connection of the line input end and the input end of each control end), if the module is bad, if not, it can be directly replaced with thin wire instead of the connection can be eliminated.
3. A multimeter can be used to directly measure whether a single module is normal. If so, it is judged as an internal short circuit between the circuit board and the module; or otherwise, if the module is broken, replace it with the module of the same model.
M. Unit board appears several lines or the whole community (unit board is divided into two communities) is not bright, long bright, dark bright
1. Visually inspect whether the corresponding pipe, core inductance and integrated circuit are unwelded, short circuit and open circuit. If so, the short circuit is disconnected and the broken welding and broken circuit is rewelded well.
2. Measure whether the voltage of the output end of each pipe is normal with multimeter (GND and the voltage of each pin); if so, determine whether the circuit of the output end of the line and the corresponding module pin is broken; if no, measure whether the input end of the pipe is normal; if so, the pipe is broken with the same type; if no, measure whether the output end of the corresponding HC138 is normal; if so, the output end of HC138 and the input end of the pipe are broken; if no, HC138 is broken.
3. Replacing the 16P line, measure whether the pin voltage 1,2,3 of HC138,4,5 (low level effective), 6 (high level effective) and integrated circuit power supply is normal, if so, it is judged that HC138 is bad, and then (2) continue to check.(4) Whether the 5V connecting line between the two communities is disconnected, if, it can be directly connected with the same power line (the general phenomenon is that the whole community is not bright and dark bright).
4. Measure whether the row signal at the input end of the unit board (goldfinger 26P can be regarded as 13 sets of rows, of which 8,9,10 and 11 are L0, L1, L2 and L3 respectively) has internal short circuit, open circuit and drive after input HC244. If so, measure whether the signal input into HC138 by HC244 drive is normal, and then check for (2), if no, judge that HC244 is broken, and replaced with an integrated circuit of the same model.
N. Unit board appears community (unit board is divided into two communities) without red or green
1. Visually inspect whether the integrated circuit and 26P row line corresponding to the fault are malwelded, broken circuit and 5V power supply are normal (it can be directly replaced with a good 26P row line).
2.26P connecting line between unit plates (1 and 2 feet of 26P row line are red signal, 3,4 feet are green signal) and the output of the front unit board (judgment method: take a long 26P theory row line cross exchange connection appears normal, Is judged to have a problem behind; conversely, Then there is a problem before) whether it is normal, so, Remeasured the input to the HC244 red signal, Drive 14 feet drive to HC595 (if, And HC595 other pins are normal, Judge that HC595 is bad, Change with the integrated circuit of the same model) if no, Then check 26P line problems and input is not normal.
O. Failure phenomenon: the unit board appears in the middle of the community (the unit board is divided into two upper and lower communities), and the two modules are missing red, green or red or green at the end.
1. Check whether the integrated circuit such as HC595 is defective, short circuit and open circuit; if so, weld the pin well.
2. Check whether the 5V power supply is normal.
3, use the multimeter to measure the corresponding input end of HC59514 feet [HC595 measurement should distinguish red green integrated circuit, order is: red, green (R, G) HC5959 feet for the signal output end, 14 The foot is the signal input end] whether the voltage is normal; so, Then judge that HC595 is bad (in other normal power supply), Replace them with integrated circuits of the same model; If no, Then check the voltage of the 9-pin output of HC595 and whether the circuit cable is disconnected, If no, Then HC595 is judged as bad, Change the HC595 IC with the same model (when replacing the IC HC595, Note that the circuit lead is not disconnected).
3. Outdoor (module) failure
1. The group is not bright or abnormal:
Check the signal direction of the first piece of abnormal module line and power cord contact is good, such as module without LED bright, indicates no power input, please check the power part (available multimeter check), such as color (color confusion) shows that the module without signal input, please check the first piece of abnormal module line input end close contact, can plug test for many times, such as problem still can switch new line.
2. Single module is not bright:
Check whether the power supply of the module is good, mainly to check whether the power socket on the module is loose. If the color confusion or color inconsistency occurs in the whole module (but there is signal input and correct picture), the signal transmission row county contact is poor, re-plug and pull out the line, or replace the tested line. If the same problem, please check for problems in the interface of the PCB board.
3. Detection method for the problem of no single light:
Use a multimeter to check whether the LED is damaged. If the light is broken, change the light according to item 5 below. Specific lighting method: the multimeter to the resistance X1, pointer multimeter black table pen to the positive LED, red table pen to the negative (digital table black pen negative, red pen positive), if the LED bright, the measured light is good, if the light is not on, the measured light is bad.
4. Maintenance of LED bad point (runaway point):
After the single lamp detection confirms LED damage, the following maintenance methods will be adopted according to the actual requirements.
4-1 positive maintenance: with the corresponding type of screw driver from the front fixed mask screw (note keep screw), remove the mask, change the lamp (please follow the following method to change the lamp), lamp and colloid sealing, restore the original mask, on the screw (screw, please pay attention not to press the lamp), finally if there is any colloid residue on the LED surface please carefully remove the colloid.
4-2 back maintenance: with the corresponding model from the back of the screwdriver from the back of the screw (note keep screw), remove the signal line, for safety please do not unplug the power cable, to prevent accidents, carefully remove the module from the hole of sheet metal to the back of the box, and then according to the positive maintenance method for single module maintenance lamp change (please follow the following lamp change method) or other maintenance.
5. Change the lights:
The LED damage around the colloid with sharp tools (such as tweezers), and make the LED pin clearly show in the line of sight, the right hand with tweezers clamp the LED, the left hand with iron (temperature is about 40 degrees, high temperature will cause damage to the LED) contact solder, and do a little stay (not more than 3 seconds, if the time but does not meet the disassembly requirements, please try again after cooling) will solder melt, with tweezers to remove the LED. Put the required LED lamp correctly into the hole of the PCB circuit board (the long foot of the LED lamp is the positive electrode, the short foot is the negative electrode, the PCB "square hole" is the LED positive pin, the "round hole" is the negative pin of the LED), melt a little solder wire, stick to the iron head, adjust the LED direction with tweezers to make it smooth, weld the solder at the LED and PCB connection, and seal the LED with the same type of colloid (PH =7).
4. Whole-screen fault:
A. Whole screen is inactive (black screen)
1. Check whether the power supply is energized.
2. Check whether the communication line is connected and whether it is wrong.(Sync screen)
3. The synchronization screen detects that the communication green light of the sending card and the receiving card does not flicker.
4, whether the computer monitor is protected, or the display field is black or pure blue.(Sync screen).
B. Whole unit board is not bright (black screen)
1. If the horizontal direction of several consecutive plates is not bright, check whether the line 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 is not bright
1. Check whether the line foot connects to the 4953 output foot.
2. Check whether the first 138 is normal.
3, check whether 4953 is hot or burned.
4. check whether there is a high level.
5. Check whether there is a connection between 138 and 4953 control feet.
D. The unit board is not bright
1. Check whether the 595 is normal.
2. Check whether the corresponding foot of the upper and lower modules is connected.
3, check 595 output foot to the module foot whether through.
E. The unit plate is uncoloured
1. Check the 245 R. G data has output.
2. Check whether the normal 595 output foot connects to the abnormal 595 input foot.
3. Check the short circuit between signals A, B, C and D.
4. Check whether the output terminal of 4953 is short circuit to other output terminals.
F. Full bright when a single or multipoint (irregular) not bright
1. Find whether the corresponding control pin of the module is short circuit to the bank.
2. Change the module or the single light.
G. One or several columns are not bright when fully bright
1. Find the pin controlling the column on the module, and test whether it is connected to the output terminal of the driver IC (74HC595 / TB62726).
2. Visually inspect whether the module pin and integrated circuit are completely welded, short circuit and open circuit; if so, weld the pin well.
3. Measure the output terminal of HC595 with a multimeter, and the output pin of HC595:1,2,3, and 4.
5. Control system failure:
1, the whole screen is not bright or appear squares
· Control whether the host machine is turned on
· Whether the communication line is well inserted properly
· Whether the sending card is already inserted
· Whether the multimedia card and the acquisition card, and the data line between the sending card are connected
· Receiving card JP1 or JP2 switch position is wrong
· Open the host
· Plug in the communication line
· Repsert the send card
· Connect the multimedia card and the collection card, and send the data lines between the cards.
· Adjust JP1, JP2 and switch position
· Whether the computer monitor is protected, or whether the display field is black or pure blue.(Sync screen)
2. Every time the LED studio is started, it is indicated that the signal acquisition line between the COM port of the control system and the data transmission card is not connected or the COM port of the computer itself is broken.
· Connect the data cable or replace the computer
3, the whole screen picture shaking or replay
· Check the communication line between the computer and the large screen
· Check the DVI line of the multimedia card and the sending card.
· Send card bad. Reinsert the communication line or replace the DVI line, replace the transmission card
Six, drive part
1, a unit board is not bright
· Whether + 5V electricity or GND is supplied
· + 5V short to GND
· 138, whether the OE signal for the fifth leg is present
· Whether the OE signal connected to 245 is normal (open circuit or short circuit);
· Power + 5V or GND
· Disconnect the short circuit
· Supply the OE signal
· Connect the open circuit and disconnect the short circuit circuit
2. The upper part or lower part of a unit board is not bright or does not display normally
· Whether the OE signal of the fifth leg of 138;
· Whether the signal of leg 11, and 12 of 74HC595 is normal (SCLK, RCK)
· Whether the connected OE signal is normal; (open circuit or short circuit)
· Double-row pins and 245, whether the connected SCLK and RCK signals are normal; (open circuit or short circuit)
· Connect the OE signal
· Connect the SCLK and RCK signals together
· Connect the open circuit and disconnect the short circuit
