Brothers who have just entered the industry must have had such a crazy moment - the display screen suddenly showed intermittent signals, and the master came over and touched them for a few seconds and said, "245 is broken", but what does this thing look like? Where is the corner of the circuit board? Last year, I made a joke when I changed the screen in the mall. I poked the 138 chip with an electric soldering iron, but the project manager scolded me so much...

​​1. What does the 245 chip look like? ​ ​

Let me teach you how to recognize your face first: the 245 chip is usually a 20-leg black rectangle with the words "74HC245" printed on the surface. Focus on three characteristics:

1. ​​Pin 1 (DIR)​​With arrow marks, control signal transmission direction
2. ​​Pin 19 (OE)​​Connect to green jumper to control the chip switch
3. There are both sides of the chip​​8 pairs of A/B ports​​, like a centipede's feet

Last month, I suffered a loss when I repaired the floor tiles screen of a music festival - I replaced the 4953 line drive as 245, and three drive boards were burned. Therefore, identifying these three characteristics can avoid detours for three years.

​​2. Where is it hidden on the circuit board? ​ ​

​​This is how outdoor advertising screens are found​​：

1. Following the cable of the receiving card, the first black chip is definitely 245
2. For double-sided circuit boards, please check them first.​​Signal input terminal​​That side
3. If you encounter a metal heat sink, 80% of them are row drives or row drive chips.

​​Transparent screen special points​​：

1. 86% transparent screen, 245 chip must be there​​Bottom signal transit area​​
2. The 245 chips of the arc-shaped splicing screen are distributed in​​Seams of each module​​
3. The weirdest thing I've ever encountered - hidden in​​Under the power module heat sink​​

​​Quick positioning method for rental screens​​：

1. Look at the "U1" or "IC1" marked on the PCB board, it is usually 245
2. Test with a multimeter​​Pin 20 (VCC)​​, 5V voltage is stable
3. Touch the chip temperature when the power is turned on, and it is normal and slightly hot (there must be a problem if it exceeds 60℃)

​​3. Why does the 245 chip burn? ​ ​

Last year, a gymnasium project burned 18 chips in a row, and the lessons of blood and tears were summarized as three major culprits:

1. ​​Unstable voltage​​: The output of the receiving card exceeds 5.5V, it must be hung in half an hour
2. ​​Electrostatic breakdown​​: Touch the chip pin with bare hands, 5000V electrostatic directly is scrapped
3. ​​Signal overload​​: More than 3 modules connected in series without relay chips

Let's focus here​​Signal direction settings​​: When the DIR pin is connected to the high level, it is A→B transmission, and when the low level is connected, it is reversed. Once when the angle of the arc screen was adjusted, the master welded the DIR foot backwards, and the entire picture was turned over, and the audience thought it was broadcasting pirated movies...

​​4. The operation of replacing the 245 chip​​

1. ​​Hot air gun temperature​​Control at 320℃±10°, don’t blow the core when blowing your feet
2. ​​Tin Belt Cleaning​​The pad must be exposed with copper color, otherwise the dummy soldering will be
3. ​​Novice's stupidity prevention method​​: Chip semicircle notch aligned with PCB marking points

There is a trick - if you encounter a chip that is suspected to be damaged, use tweezers to short-connect it​​Pin 19 (OE) to GND​​, if the screen is restored, it is confirmed that it is a 245 fault. This trick saves at least half an hour of testing during emergency repairs.

​​5. Cold knowledge that experts only know​​

1. bring​​Gold-plated pins​​The industrial-grade 245 chip has a lifespan of 3 times that of ordinary models
2. A truly high-end display will be used​​Double 245 parallel design​​, signal strength is increased by 40%
3. Brush before repairs in rainy season​​Moisture-proof firmware​​, can reduce the probability of short circuit by 70%

Last year, when I was maintaining overseas projects, I relied on the third item, which saved a whole curved advertising screen worth tens of millions during the rainy season. So, the 245 chip looks inconspicuous, but it is actually the "nerve center" of the display!

Next time you encounter a signal failure, don’t rush to deny it completely. It is absolutely correct to check the 245 chip according to these points. Really can't handle it? Contact the manufacturer directly for 24 hours of technical support - professional matters should be left to the professional team, right?

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