Technology | Why Do Red Lines Appear on LED Displays
August 5, 2025
Red lines (or red strips, red blocks) on an LED display are usually caused by hardware failures or signal transmission issues. Here are the most common causes, sorted by probability from highest to lowest:
1.Damage to individual or local LED lamp beads/chips:
This is the most common cause. An LED display consists of numerous red (R), green (G), and blue (B) three-color LED lamp beads. If the LED chip responsible for emitting red light at a certain position is damaged or has abnormal performance (e.g., short circuit), it may stay red permanently or display red irregularly.
2.Issues with internal flat cables/connectors of LED modules:
Loose connections, poor contact, cold solder joints, oxidation, physical damage (e.g., crushed, chewed by rodents), or damaged connectors in the flat cables that connect RGB lamp beads inside the LED module.
3.Issues with inter-module flat cables/connectors:
Loose connections, poor contact, cold solder joints, oxidation, physical damage, or damaged connectors (e.g., interfaces on HUB boards) in the flat cables connecting different LED modules (or unit boards). This is especially true if there is a problem with the data cable responsible for transmitting red signals.
4.Driver IC failure:
Damage to the driver chips that control the on/off state and brightness of LED lamp beads. If a driver IC (especially one controlling the red channel) malfunctions, the row or column of lamp beads it controls may behave abnormally, such as staying red permanently.
5.Power supply issues:
Unstable/low voltage: Low or unstable power supply voltage to a specific module or area may cause abnormal display in that area, sometimes (due to slight differences in voltage characteristics of LEDs of different colors).
Power module failure: Abnormal output from a switching power supply module.
Poor contact/damage to power cables: Loose or damaged power cables connecting to modules.
6.Problems with receiving cards/HUB boards:
Malfunctions in the receiving cards (which receive signals from sending cards and distribute them to modules) or HUB boards (which connect receiving cards and modules), such as damaged ports, cold solder joints, or damaged components.
7.Issues with sending cards/control systems:
Relatively rare, but failures of sending cards, bugs in control software, incorrect graphics card settings (e.g., wrong output color space), or problems with transmission cables (e.g., network cables) may also cause signal errors, leading to unwanted red displays on the screen.
8.Physical damage or environmental factors:
External impact, extrusion, moisture/liquid infiltration (causing short circuits or corrosion), long-term high temperatures (accelerating component aging), electrostatic breakdown, pest infestation, etc.
How to Preliminary Judge and Troubleshoot
1.Observe the phenomenon:
- Is the position fixed? (Yes: High probability of hardware issues; No: High probability of signal/power/software issues)
- Is it a single point, small block, entire row, entire column, or large area?
- Are the red lines always on, flickering, or changing with the screen content?
- Does the problem persist after restarting the display and control system?
2.Simple checks:
- Restart: Turn off the entire display system (including the computer with the sending card), wait a few minutes, and restart. Sometimes software or temporary errors can be resolved this way.
- Check connections: Focus on, after powering off, carefully checking whether the flat cables between modules in the red line area, and between modules and HUB boards/receiving cards, are fully inserted, have obvious physical damage (bending, breaking), or if the gold fingers are oxidized or dirty (gently wipe with an eraser). Check if power cable connections are secure.
- Swap flat cables: If inter-module flat cables are suspected to be faulty, try replacing the flat cable in the suspected faulty area with a confirmed good one.
- Swap module positions: If a module itself is suspected to be faulty (lamp beads or internal flat cables), try swapping it with an adjacent normal module of the same model. If the red line moves with the module, the module is almost certainly faulty; if the red line stays in place, the issue may be with the flat cable, HUB board, or receiving card.
- Observe power indicators: Check if the indicator lights of the switching power supplies in the corresponding area are normal (usually green).
3.Seek professional repair:
Issues such as damaged lamp beads, faulty driver ICs, damaged internal flat cables of modules, damaged receiving cards/HUB boards, or faulty power modules usually require professional LED display repair personnel for inspection and replacement.
Non-professionals should not attempt to weld or disassemble precision components, as this may cause further damage.
Summary
Red lines on an LED display are mostly caused by physical connection issues (loose, poorly connected, or damaged flat cables) or local hardware damage (individual lamp beads, driver ICs, modules). Prioritize checking connections and observing the characteristics of the abnormal area for preliminary judgment. If the issue cannot be resolved independently, contacting the display supplier or professional repair personnel is the safest approach.