Then the tools needed for unit board maintenance are multimeters, hot air guns, electric irons, soldering tins, tweezers, screwdrivers, diagonal pliers, blades, etc.
one. Unit board is not bright
1. Check if the power supply and signal cable are connected, and if the cable is broken.
2. Check that the output interface of the control card is connected incorrectly. 08 is connected to 12 or 12 to 08; whether the unit board is connected to the control card or the unit board interface has a signal and ground short circuit, which makes the interface unrecognizable. (smart test card)
3. Detect whether the 74HC245 has a short circuit or not, and the corresponding enable (EN) signal input and output pin on the 245 is soldered or short-circuited to other lines.
Note: Mainly check the power and enable (EN) signals.
two. In the oblique scan, the regular interlacing does not light up and the screen overlaps.
1. Check if the A, B, C, D signal input port to 245 is broken or short-circuited or short-circuited.
2. Detect whether there is an open circuit or a virtual solder or a short circuit between the output terminals A, B, C, and D of 245 corresponding to 245.
3. Detect whether there is a short circuit between the signals of A, B, C and D or a short circuit between the signal and the ground.
Note: The ABCD line signal is mainly detected.
three. One line or several lines are not lit when fully lit
1. Detect whether the line between 138 and 4953 is open circuit or virtual welding or short circuit.
2. The signal line to the line is interrupted and the drill is interrupted the most.
four. When scanning a line, two lines or a few lines (usually a multiple of 2, regular) are illuminated at the same time.
1. Detect whether there is a short circuit between the signals of A, B, C, and D.
2. Check if the output of the 4953 is shorted to other outputs.
Fives. Single or multiple points (irregular) are not bright when fully illuminated
1. Find the control pin corresponding to the module to measure whether it is short-circuited or soldered with the line.
2. Replace the module or single lamp.
six. One column or several columns are not lit when fully illuminated
1. Find the pin that controls the column on the module and measure whether it is connected to the output of the driver IC (74HC595).
2. Burn a short circuit with a lamp in the column, causing the whole column to be off, and the lamp or module can be replaced.
3. The column signal is interrupted by an electric drill.
Seven. Single or single column highlighting, or full line highlighting, and uncontrolled
1. Check if the column is shorted to the power ground.
2. Check if the line is shorted to the positive terminal of the power supply.
3. Replace the driver IC.
Eight. The display is confusing, but the signal output to the next board is normal.
1. Detect whether the STB latch output corresponding to 245 is connected to the latch terminal of the driver IC or the signal is shorted to other lines.
nine. Display confusion, output is not normal
1. Detect whether the clock CLK latches the STB signal for short circuit.
2. Check if the clock CLK of 245 has input and output.
3. Check if the clock signal is shorted to other lines.
Note: The main detection clock and latch signal.
ten. Display lack of color
1. Detect whether there is input and output on the data end of the color of 245.
2. Check if the data signal of the color is shorted to other lines.
3. Check whether the cascaded data port between the driver ICs of this color has an open circuit or short circuit or a virtual solder.
Note: It is easier to find the problem by using the voltage detection method, and check whether the voltage of the data port is different from the normal one, and determine the fault area.
If none of the above can be detected, you need to check the output problem. The following 4 points can be tried:
1. Check if the line from the output interface to the signal output IC is connected or shorted.
2. Check if the clock latch signal of the output port is normal.
3. Check whether the cascaded output data port between the last driver IC is connected to the data port of the output interface or short circuited.
4. Whether the output signals are shorted to each other or shorted to ground.
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