Hisense LCD TV TLM2619 no 24V voltage fault repair case - android - Phones Developers

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I was working on a Hisense LCD TV model TLM2619 that wouldn't boot with backlight, but had sound. It looked like the problem was with the high voltage board or the 24V power supply. After opening the cover and doing some measurements, I found that the power supply board wasn’t outputting 24V. I removed it for further testing and discovered that the absorption circuit in the W5667 power block had a burned CE023 2N2. I replaced it with a 1N8 and turned it on, but the 24V output was unstable, fluctuating around 10V and occasionally reaching 24V, but without any load capacity. I checked the voltage regulator optocoupler at pin 2, which showed almost no voltage. That pointed to an issue with the W5667 circuit. All components on the board were tested and seemed fine, so I suspected the W5667 itself was faulty. I bought two new ones, but replacing them didn’t fix the problem. That ruled out the W5667 as the main cause. Next, I measured the PFC voltage, which was 379V—normal. The 6th pin of W5667 had 13V, which was not normal, and the 7th pin had a 0.05V swing, also abnormal. When the 24V output was around 10V, the 7th pin voltage was low, and when it occasionally reached 24V, the 7th pin was at 1.2V. I tried supplying external 22V to the 6th pin, but the fault remained. Continuing the inspection, I removed the heat sink from W5667 and replaced it with a smaller one. When I powered it up again, I noticed a burnt smell during the measurement. Could the test leads have caused a short? I removed the W5667 and noticed the small heat sink was extremely hot. That made me realize the real issue: the W5667 was overloaded, and the culprit was the 24V transformer. I replaced the transformer and the 0.33 ohm resistor, but the W5667 immediately failed again. This time, many components were damaged. After replacing all the burnt parts, the 24V output returned to around 10V under no load. To confirm the transformer was faulty, I powered it on for five minutes, and the transformer got slightly warm, while the W5667’s heat sink stayed hot. Since the transformer wasn’t a standard part, I had to re-wind it for repair. Once everything was fixed, the 24V output stabilized at 23V on pin 6 and 1.57V on pin 7.