A Changhong G29K36 color TV was brought in with a horizontal line fault. Upon initial inspection, it was found that the horizontal output IC, N30 (LA7841), was damaged. After replacing it with a new LA7841, the unit smoked and shut down immediately. The newly installed IC was blown, indicating a possible 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 deflection circuit. Further investigation revealed a breakdown in the protective diode at the field deflection terminal—specifically VD302, a 1Z75 voltage regulator tube. If this diode fails, it can cause a short circuit that immediately damages the LA7841. After replacing the faulty diode, the TV was tested and worked properly. Additionally, a Hisense color TV exhibited similar symptoms. If the power block continues to burn out repeatedly, it's important to check whether the diode is leaking or has failed, as this can be a common cause of such failures.
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