TCL color TV screen only blue green color alone lacks red strange fault sharing - android - Phones Developers

These days, the misty rain in Shantou, South China, feels a bit like the famous "West Lake March Day." The temperature is mild, ranging from 12 to 18°C. Drizzles gently blow outside the window, carrying the scent of blooming flowers and plants, creating a soft symphony of nature. Sipping a rich cup of Kung Fu tea with a friend by my side, the atmosphere is truly relaxing and pleasant.

The phone rings — it's the CEO of a cosmetics company. He says his home TV is broken, and since it's his father’s, he needs me to come over. According to the appointment, the 34-inch TCL high-definition TV is on, but the image is only blue-green, with red appearing purple. The sound is normal, though. He mentioned that he rarely repairs appliances these days and didn’t want to ask me directly. Instead, he called two technicians, both of whom said the same thing: “It's like the old ones!”

Originally, he wanted to replace the LCD, but his father insisted the current TV was still good, saying the picture wasn’t bright enough and even joked that Yao Ming would look like a dwarf on it. He believed the color was still good and wanted to fix it instead of replacing it. The boss also has some basic knowledge of electronics and knows the TV is less than five years old, so there's no reason to throw it away.

After disassembling the TV, I checked the three-color outputs. R output was 175V, G was 152V, and B was similar to G. The RGB excitation voltage was around 2.3V, which seemed normal. It wasn't a color difference output cutoff, so the problem must be in the output board.

Upon further analysis, if the R output were cut off, the voltage should have been around 200V, but it was only 175V. That suggests the emission capability of the R gun might have decreased. However, the father mentioned that it worked fine just a few days ago.

In my experience, things don’t usually fail overnight without any reason. Like the cordless phone transformer at the boss’s home, which works perfectly at 7.5V. All three guns showed similar voltages, so the tube still looked healthy and promising.

I replaced the output IC and checked all related bypass capacitors and clamping circuits, including ABl. Nothing unusual was found. This really felt like an ancient mystery — “Like the ancients”! Haha, after more than 20 years in the repair industry, can you really stump me?

As I smoked a cigarette and sipped my tea, I smiled. High-definition video tubes are special, and sometimes strange faults come from unexpected places. I decided to check the tube seat. When I removed it, I saw the issue immediately — the connection for FOUS2 had completely broken!

Quickly replacing the tube seat, the image came back to life, vibrant and clear. The boss’s father smiled, showing his teeth — not because of the TV, but because he finally got what he wanted. He handed his son a half-smoked Chinese cigarette and said, “Look, this TV is still good.” The boss had no words left.

The TV was fixed, and although there were no words of praise, there was one question I needed to discuss with experts:

Why does the loss of voltage in FOUS2 cause a drop in R output current while G and B remain normal? I’d appreciate any insights from the masters. Tip: Due to the unique nature of high-definition video tubes, some faults differ from those in traditional CRTs. So when circuit behavior seems normal, sometimes checking the tube seat can make all the difference!