Maintenance Tip: This machine uses a bus control circuit. Abnormal CPU power supply can cause operational confusion; therefore, even if the +B (110V) voltage returns to normal, you should not ignore whether the standby state power supply is functioning properly.
Beijing Konka TV After-sales Service Center Case on September 23, 2011.
Solution: Replacing C821 resolved the fault.
Analysis and Maintenance: When the fault occurred, the voltage at the +B output terminal was found to be lower than normal, leading to suspicion of a fault in the flyback transformer's boost winding. However, replacing the flyback transformer did not resolve the issue. Since the linear regulation of this machine is controlled by the CPU, we checked the CPU. During the standby state, the voltage of the +10V circuit was only 0.6V, and the voltage of the +5V circuit was also low. We determined that there was an abnormality in the standby voltage of the switch-mode power supply. Measuring key points in the switch-mode power supply, such as both ends of C821 and C845, we found that the voltage of C821 was 55V (normally it should be 6.2V). After removing C821 for measurement, it was found to have leakage.
For the Konka T3488N TV, after working for a while and then shutting down, when turned on again, the image becomes larger, and during standby, there is a sound of relay engagement.