Ouch hey! Has your LED screen suddenly turned into a "zebra crossing"? The upper half is so bright that it is dazzling, and the lower half is as black as if it is powered off. Don't rush to find a hammer to smash the screen! Let's talk about it today​Interlaced lines show where the seven inches of the fault is​​, please make sure you slap your thighs after listening: "It turns out that repairing screens is easier than repairing air conditioners!"

1. Grasp the "culprit" first: These 5 places are the most likely to cause trouble

Don’t panic when you encounter the interlaced line. Pick up the screwdriver and follow me. Last year, a shopping mall had this problem with the large screen. The maintenance team failed to repair it for three days, but finally found that it was just a cable plug that was incorrect...

​Troubleshooting rankings TOP5:​

1. ​Poor signal line contact​(38%)
   • Symptoms: Random horizontal stripes on the screen, you may recover if you take a few shots.
   • Quick detection: Whether the "click" sound is crisp when unplugging the cable
2. ​​Control chip virtual soldering​(27%)
   • Focus on checking the 74HC245/138 chip, and use a multimeter to measure whether the voltage on the first pin is about 2.5V.
3. ​​The power supply is unstable​（19%）
   • Pay special attention to outdoor screens! Voltage fluctuations exceed ±5% will make you a monster
4. ​​Program settings exhaust​（11%）
   • The grayscale settings are incorrect and the refresh rate parameters are tampered with the most serious
5. ​Physical damage disorder​（5%）
   • Transport collision results in microcracks on PCB boards, which are difficult to detect with naked eyes

Here is a tip for saving money -​The principle of soft first and hard first​. When encountering problems, don’t rush to disassemble the machine. Restarting the control system + reinstalling the driver can solve 30% of pseudo-faults!

2. Step-by-step teaching: three-step positioning problem without placing pitfalls

Last year, I helped my friend repair the large screen in the gymnasium, which was done in two days, saving 20,000 yuan from the quotation of the maintenance company.

​Three tricks to diagnose:​

1. ​​View the regularity of symptoms​​
   • 1 line is bright and 1 line? Check the A signal path
   • 2 lines are bright and 2 lines? Focus on B signal
2. ​Touch the chip temperature​
   • The normal working 74HC138 temperature is about 40℃, and there will be problems when it is hot
3. ​​Multimeter four-step method​
   • Measure the power supply voltage → check the signal path → measure the chip pin → check the wire resistance value

For example, a regular interlaced dark area appeared on the floor tiles on a stage. A multimeter was used to measure the voltage at the output end of the 4953 driver chip, and it saved 8,000 yuan of repair costs immediately after replacement.

3. Repair and anti-pit guide: Don’t try these tricks

I have seen too many young men turn the screen into bricks and tell me some bloody lessons:

• ​​Electric operation is a taboo​! A master once fired three control cards without powering off the chip.
• ​​Flying lines are connected randomly to destroy everything​! If you use a network cable instead of a cable, the full screen will be filled with snow in three months.
• ​​Blindly replace IC chips​​! 74HC245 and 74HC138 look similar but have different functions. They directly emit smoke when mixed installation

There is a dark story here—​​The deepest pit of second-hand refurbished chips​​! Last month, a repair site used a refurbished 74HC595 chip, but it failed after installing it for 72 hours. I will teach you a unique way to identify the edges of genuine chips: the corners of the original chip are polished smoothly, and the refurbished products often have traces of laser lettering.

4. Prevention is better than treatment: daily maintenance three-piece set

All good screens are raised! Refer to the maintenance plan of an international event venue:

1. ​​Monthly physical examination​​: Use a thermal imager to scan and detect abnormal temperature points early
2. ​​Moistureproof secrets​​: The southern plum rainy season turns on for 2 hours a day to drive away the moisture
3. ​Parameter backup​: Save three sets of configuration files after each debugging

Suddenly I thought of a real thing: because the LED screen of a certain theater does not need to be damp for a long time, the interlaced display + color ratio double-killed, and it cost 18,000 yuan just to dry it. So,​The screen looks like a girlfriend—I will really get angry after being neglected for a long time​​！

Editor's opinion: LED screens are no longer "iron bumps",​Intelligent diagnosis is the king​. I heard that some high-end models can automatically detect ABCD line signal abnormalities, and the fault positioning accuracy reaches the chip level. Next time I choose the screen, I might as well ask if there is any "self-test black technology" that can save real money at critical moments!

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