It is the first time for a newbie to debug a large LED screen, and he is most afraid of encountering a situation where the picture is normal but the subtitles are not displayed. Just like a novice who has just learned how to shoot short videos and how to quickly gain fans is always stuck on content positioning, not understanding equipment issues is really a headache. Last week, there was an outdoor advertising screen that was just installed in a shopping mall. It was playing a promotional video but no promotional information. The person in charge was so worried that he broke out in a cold sweat. Today we will break it down and talk about this common and heartbreaking failure.

Let’s start with a real case: When a fence screen was installed at a stadium in Tokyo last year, the strange phenomenon of subtitles disappearing suddenly occurred during the debugging phase. It took the engineer three days to discover that the version of the signal distributor did not match - this kind of devil hidden in the details is the most frustrating thing for novices. Next, we will troubleshoot the problem in four dimensions. Remember to take a small notebook to write down the key points.

​​The first step is to look at the hardware connections.​ ​. Just like a mobile phone charging cable cannot be charged due to poor contact, the disappearance of subtitles on the LED screen is probably related to the wiring. Check whether the HDMI cable from the video processor to the sending card is tightly plugged in, especially if outdoor equipment is prone to loosening after being transported. Here’s a little trivia: Nowadays, mainstream equipment on the market uses 12G-SDI interfaces to transmit 4K signals. If ordinary network cables are used instead of dedicated coaxial cables, data packets will be lost if the transmission distance exceeds 30 meters.

​​The second step is to check the software settings.​ ​. The most outrageous case I have ever encountered was that the engineer set the transparency of the subtitle layer to 99%, which was completely invisible to the naked eye. Here are three must-check items for you: 1. The subtitle file format must be supported by the system (such as .srt or .ass) 2. The layer overlay sequence must put the subtitles at the top 3. The rendering mode of the playback software must be "Hardware Acceleration". If you use an old computer from ten years ago to run 8K content, it will be a matter of minutes if the screen freezes and drops frames.

​​Signal synchronization issues are most easily overlooked​ ​. Last year, a curved advertising screen in Singapore suffered from this problem - the synchronization clocks of the sending card and receiving card were not calibrated, causing the subtitles to be half a second slower than the picture. Let me teach you a simple method: take a picture of the screen in slow motion mode on your mobile phone. If you find that there are black scanning lines moving in the subtitle area, quickly check whether the refresh rate of the device is consistent. Nowadays, high-end screens can achieve a refresh rate of 1920Hz, but if the driver IC does not adjust the parameters properly, trouble will still occur.

Speaking of the driver IC, this is the "brain" of the display. A while ago, there was a theater where the subtitles on the floor tile screen came and went. When I took it apart, I found that poor heat dissipation caused the driver chip to be soldered. Here is a reminder: Do not install indoor screens in locations exposed to direct sunlight. The temperature control module will activate the protection mechanism if it exceeds 50°C. Now the industry's leading technology can achieve ultra-low power consumption of 0.8W/㎡, and the calorific value is more than 40% lower than that of traditional products.

If the problem remains unresolved after all the above investigations, it’s time to resort to the ultimate trick—the segmented detection method. First, connect the sending card directly to a single module. If there is no problem, gradually increase the number of connected modules. The cylindrical advertising screen installed in Dubai Mall last year used this method to detect that the third section of the signal amplifier was burned out. Remember: a screen with intelligent brightness adjustment (such as one that can automatically adjust 800-1200 nits) may turn off some functional modules in low-brightness mode. At this time, you need to enter the engineering mode to remove the restrictions.

A friend wants to ask: "Why does it work well during debugging but causes problems when it is officially used?" "This situation is mostly caused by the power configuration. For example, the fence screen used in sports venues can have an instantaneous starting current that can reach three times that of normal operation. If the distribution box does not leave enough margin, the subtitle drive circuit will stop due to voltage instability. Nowadays, new cabinets are made of magnesium-zinc alloy, and with a quick disassembly and assembly design, it only takes ten minutes to temporarily add a voltage regulator.

The editor finally has something to say from the bottom of my heart: If you encounter a problem, don’t deal with it yourself, contact the manufacturer’s technical team as soon as possible. Those who say 24-hour response are really not bragging. At 2 a.m. last Christmas, there were engineers remotely guiding Korean customers to change parameters. After all, when it comes to display devices, stability and technical support are king. Do you think this is true?

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