Talking about how to properly repair the TV (2) TB1306 understanding - android - Phones Developers

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When it comes to repairing a TV, especially models using the TB1306 in high-definition CRT systems, understanding the field scan driver is crucial. Unlike the TDA9332, which doesn’t rely on the SDA/SCL bus for field drive output, the TB1306 requires a feedback signal from the line to function properly. This means that even if the power supply and surrounding components are normal, the absence of a feedback signal can lead to issues like a cloudy screen or no image at all.

For example, consider a Skyworth 6D85 model experiencing clouding during startup. This usually indicates an issue with the field drive. If left unaddressed, it may eventually cause damage to the picture tube. A common approach is to disconnect the field deflection coil temporarily and use an oscilloscope to check for DC output or waveform presence. If there's no waveform on the VD signal of the digital board, it’s likely that the line feedback is missing.

During troubleshooting, a faulty voltage regulator in the line feedback circuit was identified and replaced, resolving the issue. It’s important to note that in some cases, the field drive output of the scan block (whether using TDA9332 or TB1306) isn't controlled by field feedback, so checking the feedback loop is essential for accurate diagnosis.

Another case involved a Changhong CHD29866 model showing a green horizontal line. After replacing the STV9381 and TB1307 chips on the digital board, the issue persisted. The solution required checking the field output circuit, where a missing feedback resistor was found. Adjusting the power supplies and field amplitude helped resolve the problem.

One user shared their experience on a forum, explaining that the field wasn’t working without a proper line pulse. They noted that the theory behind such faults often suggests that a horizontal bright line isn’t directly related to the field block. In some cases, a faulty chip or misaligned deflection could cause similar symptoms.

This kind of troubleshooting highlights the importance of understanding the specific behavior of each component. Without a clear feedback signal, the TB1306 won’t produce the necessary field drive, making it critical to trace the source of the problem accurately. Using tools like an oscilloscope can greatly simplify this process, helping technicians quickly identify and fix scan-related issues.