It's been a while since I last posted here, but I'm back to share an emergency repair I did on a color TV that had no characters on the screen. The approach I took was more of a "shifting wood" style maintenance—no real advanced techniques, just trial and error. As they say, sometimes it's all about intuition and experience.
The TV in question is a Changhong 1238 model with a CHT0827 CPU. The user reported color issues, and when the TV was turned on, it showed a system setting error. However, there was no response when pressing any buttons, which made me think the remote control might be faulty.
I tried using the original remote, but nothing worked. So I used a remote detector, and it confirmed the remote was functioning properly. Then, by accident, I pressed the standby button, and the TV turned off. Pressing it again turned it back on. When I tried adjusting the volume, the sound decreased, but no volume icon appeared, and there were still no characters on the screen.
After opening the case, I carefully examined the internal components. I noticed that there was no inductor between the CPU crystal and other parts. I suspected this might be the character oscillation inductor. I removed the Zhongzhou (a common part in these TVs), and found that the coil wasn't broken, but one of the attached tubular capacitors had leaked badly, with a resistance of only 20 ohms. Replacing it immediately restored the character display, which was a big relief!
However, the character position was still off. The video in the upper right corner was centered on the screen. I thought maybe I needed to adjust the timing or the signal path. I grabbed a 47PF blackhead capacitor from the high-frequency head and connected it. That improved the display slightly, but it was still not perfect.
So I tried another 82PF blackhead capacitor, connecting it in series with the 47PF one. This time, the character display was almost back to normal. These two capacitors are actually the IF output coupling capacitors from the high-frequency section. Since the TV doesn’t require RF reception, removing them didn’t affect the overall performance.
Finally, I used the remote control to enter the menu and adjusted the color system from NTSC 4.43 to the automatic setting. Everything returned to normal, and the TV was working as expected. It was a good reminder that sometimes, even simple fixes can make a big difference.
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