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

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Repairing a TV, specifically the TB1306 field driver in high-definition CRT machines, can be quite challenging. While many TVs use TDA9332 for field scanning, the TB1306 operates differently. Unlike TDA9332, which doesn’t rely on SDA/SCL bus control for the field drive, the TB1306 requires a line feedback signal to generate output. This is a crucial point that often leads to confusion during troubleshooting.

For example, in a Skyworth 6D85 model, a common issue is the appearance of "cloud" on the screen during startup. This usually indicates an abnormal field operation. If left unattended, it may even cause damage to the picture tube. In such cases, it’s recommended to disconnect the field deflection coil temporarily while diagnosing the problem. Observing the field output with an oscilloscope or checking for DC voltage without measuring directly can help identify the root cause.

When using an oscilloscope to check the field drive output (VD) from the digital board, if no waveform is detected, it suggests that the line feedback signal is missing. A thorough inspection of the line feedback circuit revealed a faulty voltage-stabilizing tube. Replacing it resolved the issue effectively.

It’s important to note that in HD machines using TDA9332 or TB1306, the field output isn't typically controlled by feedback signals. However, for TB1306, the presence of a working line signal is essential for proper field drive output. Another case involved a user experiencing a green horizontal line on a Changhong CHD29866 TV. After replacing the STV9381 and TB1307 chips, the issue persisted. The solution came down to checking the field output circuit, where a simple resistor was overlooked, leading to the problem.

In some cases, users might think the issue lies in the field block itself, but the real problem could be a missing line pulse. Understanding the characteristics of the TB1306 is key here. Without proper line feedback, the field drive won’t function, even if all other components appear normal. This highlights the importance of checking the line feedback circuit carefully, especially when dealing with complex issues like this.