A Changhong G29K36 color TV was brought in with a horizontal line fault. Upon initial inspection, the N30 IC (LA7841) was found to be damaged. After replacing it with a new LA7841, the power supply block smoked and the TV shut down immediately. The newly installed IC was also blown, indicating there might be a short circuit or overvoltage issue in the circuit. The field supply voltage was measured at 28V, which is normal under load conditions. No issues were found in the output section of the field circuit. Further investigation revealed that the deflection diode at the field deflection terminal had a problem. Specifically, the protective Zener diode VD302 (1Z75) had failed and broken down. This breakdown likely caused a short circuit, which led to the immediate failure of the LA7841 IC. After replacing the faulty diode, the TV was tested again, and the issue was resolved. Additionally, a Hisense color TV exhibited similar symptoms. If the power IC keeps burning repeatedly, it's important to check if the Zener diode is leaking or has failed, as this can cause repeated damage to the main IC. Always make sure to thoroughly test all components before re-installing any ICs to avoid further damage.
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