86191xxxxxxxx

Common Faults of LED Display Board

Created on 09.24

LED Panel Fault Troubleshooting

(1) Entire panel fails to light up

Check whether the connections of the power supply and signal cables are normal.
Verify if the test card can recognize the interface. A flashing red light on the test card indicates recognition failure. In this case, check whether the lamp panel and test card share the same power ground, or if there is a short circuit between the signal and ground at the lamp panel interface which causes interface recognition failure.
Inspect the 74HC245 chip for cold solder joints or short circuits, and check whether the corresponding enable signal input/output pins on 74HC245 have cold solder joints or short circuits to other circuits. Note: Priority should be given to checking the power supply and enable signals.

(2) Regular alternate rows remain off with overlapping images during dot/line scanning

Check for broken wires, cold solder joints or short circuits between the A, B, C, D signal input ports and 74HC245.
Inspect for open circuits, cold solder joints or short circuits between the corresponding A, B, C, D output terminals of the 74HC245 chip and 74HC138.
Check whether there is a short circuit among A, B, C, D signals, or if any signal is shorted to ground. Note: Priority should be given to inspecting the A, B, C, D row signals.

(3) One or several rows do not light up under full-bright mode. Check for open circuits, cold solder joints or short circuits on the circuits between the 74HC138 chip and 74HC4953.

(4) Two or several rows (usually multiples of 2, showing regular patterns) light up simultaneously during row scanning

Check whether there is a short circuit among A, B, C, D signals.
Inspect if the output terminal of the 74HC4953 chip is shorted to other output terminals.

(5) Single or multiple irregular dark spots under full-bright mode

Locate the control pin corresponding to this module and measure if it is shorted to its row.
Replace the module or individual LED lamp.

(6) One or several columns do not light up under full-bright modeLocate the pins controlling this column on the module, and check the connection to the output terminal of the driver IC (74HC595 / TB62726).

(7) Single dot / single column high brightness, or entire row high brightness out of control

Check whether this column is shorted to power ground.
Inspect if this row is shorted to positive power supply.
Replace the corresponding driver IC.

(8) Display is garbled, while signals output to the next panel are normal. Check whether the STB latch output terminal of the 74HC245 chip is connected to the latch terminal of the driver IC, or if the signal is shorted to other circuits.

(9) Garbled display with abnormal output

Check whether the clock signal and latch signal are shorted.
Verify if the clock signal of the 74HC245 chip has normal input and output.
Inspect if the clock signal is shorted to other circuits. Note: Priority should be given to checking the clock and latch signals.

(10) Color missing on display

Check if the corresponding color data pins of the 74HC245 chip have normal input/output.
Inspect whether the corresponding color data signal is shorted to other circuits.
Check for open circuits, short circuits or cold solder joints on cascading data ports between driver ICs for the corresponding color. Note: The voltage test method helps locate faults efficiently. Compare the voltage of data ports against normal values to confirm the faulty area.

(11) Faulty output

Check the connection and short-circuit status of circuits from the output port to driver ICs.
Verify whether the clock signal and latch signal of the output port work normally.
Check whether the cascaded output data port of the last driver IC connects to or short-circuits the data port of the output interface.
Check if output signals are shorted to each other or to ground.
Inspect the condition of the output ribbon cable.

Contact

Leave your information and we will contact you.