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Common fault and maintenance of LED displays

Common Fault and Maintenance of LED Displays

An LED display consists of a computer control unit, display drive hardware, LED display matrix and power supply four major functional parts.

Most parts which more likely go wrong are:

1. Interface

Symptoms: Computer information can not be displayed.

Solution: check signal cable connection, reconnect it.

2. Power Supply

Symptoms: Computer information can not be displayed.

Solution: check power cable connection, reconnect it.

3. Drive

Symptoms: Certain row or column are not working.

Problem: The corresponding drive circuit (chip) malfunctions

Solution: Replace it with good-condition drive IC

4. Showing problem

Symptoms: Some LED lamps might be damaged after long-time use.

Solution: maintenance or replace disfunctional ones.

Diagnosis and Troubleshooting Process of LED Displays:

1, Check if your display control system is a synchronous or an asynchronous one;

For a synchronous display, you should check whether the monitor's settings are changed or not, whether the communication is working or not.

For a asynchronous display, first of all, you should check whether the parameters of the display, hardware address, width, height and IP are altered, and then test if control unit is working.

2, Check if your display is partially disfunctional or the entire screen display is not working;

Part of the display is not working which rules out communication failure, usually it's symptoms of display hardware failure.

For disfunction of an entire screen, there may be many reasons.

Display unit board interface

The display is composed of LED modules, the signal is transmitted by the flat cable.

Cell Board Interface Descriptions: N = GND, L = Latch or ST, S = Clock (Clk), O = Enable (OE), E = Enable (/ OE), R = red data, G = green data, U = blue data, ABCD = row signal, H = decoded row signal, F = floating, V = VCC)


1. Display unit board maintenance

1)Symptoms: Display unit board is not working. Problems: There may be no power connection. Input interface 74HC245 is damaged, OE signal is high-level input because of short circuit.

2)Symptoms: Certain line of an LED module stays on. Problems: Decoder, 74HC245, LS138.

3)Symptoms: A row of an LED module stays on. Problems: 4953, LS138 goes wrong or power cable disconnected.

4)Symptoms: a rank is not working. Problems: Pseudo Soldering of HC595, 8026.

2. Synchronized video system

1)Symptoms: The computer is working, the screen is not. Problems: the communication is faulty (such as the connection is not good).

2)Symptoms: The computer is working, the display flashes, but no signal. Problems: The software LEDSETUP did not start.

3)Symptoms: The display is normal, but the whole screen is flashing. Problems: communication line, sending card, receiving card or receiving card is faulty.

4)Symptoms: Display color is abnormal. Problems: There is a problem with the display mode setting.

5)Symptoms: A part of the display is abnormal. Problems: Check the corresponding scanner board, there may be no power, or HC245 is faulty, or it may be damaged.

3. Asynchronous text screen system

1)Symptoms: No display while computer is working. Problems: The main control board may have no power supply or input voltage is too low.

2)Symptoms: The old contents is displaying but communication is faulty. Problems: the communication line is abnormal, the wiring is wrong. Communication interface chip 232 malfunctions or computer communication interface malfunctions.

3)Symptoms: Loss of content. Problems: 3.6V battery is dead.

The above is common failures, customers generally can solve them on their own.