LED display unit board:
A, the entire board is not bright
1. Check the power supply and signal cable is connected.
2, check whether the test can identify the interface card, flashing red test card is not recognized, check whether the lamp board test card with power, or in light board interfaces have signal and ground lead to a short circuit can not recognize the interface. (Intelligent Test Card)
3, detecting the presence or absence 74HC245 Weld short circuit, if the 245 corresponding enable (EN) signal input and output pin Weld or shorted to other lines.
NOTE: The main check the power and enable (EN) signals.
B, at the point oblique scanning, regular interlaced display overlapping does not shine
1. Check the A, B, C, D signal input port to have a break or whether Weld, short-circuiting between the 245.
2, testing 245 corresponding A, B, C, D output terminal 138 and the short or Weld, break.
3, if a short circuit or a short circuit between the signal and ground detection A, B, C, D each signal.
NOTE: The main testing line AB CD signal.
C, when all bright a line or lines does not shine
1, the detection circuit 138-4953 Weld between whether open or short circuit.
D, when the line scan, two lines or lines (usually a multiple of 2, there is regularity) simultaneously lighting
1, if a short circuit is detected between A, B, C, D of each signal.
2, testing whether the 4953 output and other output short circuit.
E, there is a single point or multi-point (irregular) at full light does not shine
1, to find whether the module corresponds to the Bank's short-circuit measurement and control pin.
2, the replacement module or a single lamp.
F, when there is a full light does not shine or a few columns
1. Find the column control pin on the module, measuring whether the driver IC (74HC595 / TB62726) output terminal.
G, there is a single point or single highlight, or the entire line is highlighted, and not controlled
1, check whether the column is short-circuited and the power ground.
2, testing whether the line short-circuit the positive supply voltage.
3, to replace its driver IC.
H, display confusion, but the output signal is normal to the next line
1, 245 corresponding to the detected output of the latch side STB latch and driver IC is connected or the signal is shorted to other lines.
I, display confusion, the output is not normal
1, the detection clock signal CLK STB latch short circuit.
2, testing whether there is a clock CLK 245 input and output.
3, the detection clock signal is shorted to other lines.
Note: The main clock and latch signal detection.
J, lack of color display
1, 245 detect the color data end if there is input and output.
2, testing the color data signal is shorted to other lines.
3, whether there are open or shorted, Weld-level data to detect even the color of the mouth between the driver IC.
Note: You can use the voltage detection method is easier to find the problem, test the voltage data port is different than normal, identify the problem areas.
K, output in question
1, the detection output interface to the signal output of the IC is connected or short circuit.
2, the detection output latch clock signal is normal.
3. The last driver to detect whether data cascaded output data interface port and output port connection between IC or short circuit.
4, the output signal if there is mutual short-circuit or shorted to ground.
5, check the output of the cable is good.