This article lists the processing methods of various problems of LED display, including short circuit processing, unit board failure processing, outdoor (module) failure processing, the whole screen failure processing, control system failure processing, drive part of the problem processing and so on. More detailed worth collecting.
Judgment problems must be dealt with first after the main way, will be obvious, serious first, small problems after processing. (Short circuit should be the highest priority.
1, resistance detection method, the multimeter to the resistance file, detect a normal circuit board of a point of resistance to ground value, and then detect another board of the same point test and the normal resistance value is different, if different then determine the scope of the problem.
2, voltage detection method, the multimeter to the voltage file, detect the suspected problem of a point of the circuit to the ground voltage, compare whether the normal value is similar, or determine the extent of the problem.
3, short-circuit detection method, the multimeter to short-circuit detection gear (some are diode voltage drop file or resistance file, generally with an alarm function), to detect whether the phenomenon of a short circuit, the discovery of a short circuit should be resolved as a matter of priority, so that it does not burn other devices. The method must be operated in the case of circuit power failure, to avoid damage to the table.
4, voltage drop detection method, the multimeter to the diode voltage drop detection file, because all the IC is composed of the basic numerous unit parts, only miniaturized, so in when it has a current through a pin, there will be a voltage drop on the pin. Generally the same model of IC on the same pin voltage drop is similar, according to the value of the voltage drop on the pin to compare good or bad, the circuit must be powered off to operate. The method has certain limitations, such as the device being tested is high resistance, it will not be detected.
Second, the unit board failure.
A. The whole board does not light
1, check whether the power supply and signal lines are connected.
2, check whether the test card to identify the interface, the test card red light flashing is not identified, check whether the light board with the test card with power ground, or light board interface has a signal and ground short-circuit resulting in the inability to identify the interface. (Intelligent test card)
3, test 74HC245 has no deficient solder short circuit, 245 on the corresponding enable (EN) signal input and output feet whether deficient solder or short circuit to other lines. Note: Mainly check the power supply and enable (EN) signal.
B. In the point diagonal scan, the regular interlaced not light display screen overlap
1, check the A, B, C, D signal input port to 245 whether there is a broken line or dummy solder, short circuit.
2, detect whether there is a break or dummy solder or short circuit between 245 corresponding A, B, C, D output and 138.
3, detect whether there is a short circuit between A, B, C, D signals or a signal and ground short circuit. Note: The main detection ABCD line sign
C. All light when there is a line or a few lines do not light
Detect whether the line between 138 and 4953 is broken or false solder, short circuit.
D. In the line scan, two lines or several lines (generally a multiple of 2, with regularity) while lighting
1, test A, B, C, D whether the signal between the short circuit.
detect whether the output of 4953 is short-circuited with other outputs.
E. When the full light has a single point or multi-point (irregular) does not light
1、 Find the corresponding control pin of the module to measure whether it is short-circuited with this line.
2, replace the module or single light.
F. When the full light has a column or columns do not light up
Find the control pin of the column on the module, and measure whether it is connected to the driver IC (74HC595/TB62726……) The output is connected.
G. There is a single point or a single column highlighted, or the entire line highlighted, and not controlled
Check whether the column is shorted to power ground.
2、 Check whether the line is shorted with the power supply positive pole.
Replace the driver IC.
H. Display confusion, but the output signal to the next board is normal
Detect whether the latch output of 245 corresponding STB is connected to the latch end of the driver IC or the signal is short-circuited to other lines.
I. The display is confused and the output is not normal
1、 Detect whether the clock CLK latch STB signal is short-circuited.
2、 Detect whether the clock CLK of 245 has input and output.
3、 Detect whether the clock signal is short-circuited to other lines. Note: The main detection clock and latch signal.
J. Display missing color
1、 Detect whether there is input and output of the data side of the color of 245.
2、 Detect whether the data signal of the color is short-circuited to other lines.
3, detect whether there is a break or short circuit or false solder between the cascade data port of the color driver IC.
(Note: You can use the voltage detection method is easier to find the problem, test the voltage of the data port and whether the normal is different, to determine the fault area.)
K. Output problems
1, test the output interface to the signal output IC line is connected or short-circuit.
2, detect whether the clock latch signal of the output port is normal.
3、 Detect whether the cascade output data port between the last driver IC is connected to the data port of the output interface or whether it is short-circuited.
4、 Check whether the output signals are shorted to each other or shorted to ground.
5、 Check whether the output line is good.
L. Unit board appears eight points or 16 points row, column or single point is not bright, long bright, dark bright
1, visual inspection of the module pins and leads corresponding to the fault have a short circuit, false solder, broken circuit.
2, each cell (cell board is divided into two cells) of the upper and lower, left and right modules between the common connection line is normal (set the multimeter with the ringing end, measuring the module line input and each control input lead connection), if so, the module is judged to be bad, such as no, can be directly connected with a thin wire instead of eliminating.
3, available multimeter directly measure whether a single module is normal, if so, the board is judged to be an internal short circuit between the module, such as otherwise judged to be a bad module, with the same type of module replacement.
M. The unit board appears several lines or the whole cell (the unit board is divided into two cells) does not light, long light, dark light
1, visual inspection of the corresponding line tube, through the heart of the inductor, integrated circuit is a false solder, short circuit, break, if so, the short circuit will be disconnected and false solder, break re-welded.
2, using a multimeter to measure the voltage of the output of each line tube is normal (multimeter measurement method: black pen to GND, red pen to measure the voltage of each pin); if yes, the line output and the corresponding module pin break; if not, measuring the input of the line tube is normal; if yes, the line tube is bad, with the same type of line tube to replace it; if not, measuring the output of the corresponding HC138 is normal; if not, measuring the output of the HC138 is normal; If yes, the output of the HC138 and the line tube is judged to be broken; if not, the HC138 is judged to be bad.
3, replace the 16P line with a good try, measure the HC138 address input terminal 1, 2, 3 pin voltage, select terminal 4, 5 (active low level), 6 (active high level) and integrated circuit power supply is normal, if so, the HC138 is judged to be bad, then (2) continue to check. (4) whether the 5V connection between the two cells is disconnected, if so, can be directly connected with the same power line (the general phenomenon of the whole cell is not light, dark light).
4, measuring the line signal at the input of the unit board (gold finger 26P can be regarded as 13 groups, of which 8, 9, 10, 11 are L0, L1, L2, L3 four groups of line signal) there is no internal short circuit, disconnection and input HC244 after the drive is normal, if so, then measure the HC244 drive input HC138 signal is normal, and then (2) continue to check, if not, the judgment is HC244 bad, replace with the same type of integrated circuit.
N. cell board appears cell (cell board is divided into two cells) no red or no green
1, visual inspection of the failure of the corresponding integrated circuit, 26P line has no solder, broken and 5V power supply is normal (can be replaced directly with a good 26P line).
2, the 26P connection line between the unit board (26P row of 1, 2 feet for the red signal, 3, 4 feet for the green signal) and the front of the unit board output (judgment method: take a long 26P theory row of cross-connected normal, it is judged that there is a problem behind; vice versa, there is a problem in front) is normal, if so, and then measure the input to HC244 red signal, after the driver sent to HC595 (If yes, and HC595 other pins are normal, HC595 is judged to be bad, with the same type of integrated circuit to replace) If not, check the 26P line has problems and input is not normal.
O. Fault phenomenon: the unit board cell (cell board divided into two cells) in the middle of the upper and lower two modules are lack of red, green or from the abnormal to the last are lack of red, green.
1, the visual inspection of the unit board corresponding to the failure of the integrated circuit such as HC595 is not a false solder, short circuit, break; if so, the pins will be soldered.
2, test the 5V power supply is normal.
3, using a multimeter to measure the fault corresponds to the HC595 input 14 feet [HC595 measurement should be distinguished from the red strain IC, the order of arrangement: red, green (R, G) HC595 9 feet for the signal output, 14 feet for the signal input] voltage is normal; if yes, the judgment of HC595 bad (in the case of other normal power supply), with the same type of integrated circuit replacement; if no, then the judgment of HC595 bad (in the case of other normal power supply); If not, check the voltage at the 9-pin output of the corresponding HC595 in front, and the circuit connection line is not disconnected, if not, it is judged that HC595 bad, with the same type of HC595 integrated circuit to replace (replace the integrated circuit HC595, pay attention to the circuit leads do not break)
