At 7 PM tonight, a customer brought in a Skyworth LCD TV model 32E55HM for repair. The unit had a red light that blinked, and it wouldn’t turn on with the remote or the standby button. When the customer arrived, he asked about the repair cost. I told him the lowest price I could offer, but he still tried to negotiate. I finally refused and let him decide whether to proceed or not.
After opening the unit, I tested the power supply. The voltage on the filter capacitor was 350V, which was normal. This model doesn’t have a PFC circuit. The power IC used is TEA1733P. I measured the voltage at pin 1 and found it at 20V, while pin 5 only showed 2.3V. I wasn’t sure if this was normal, but something didn’t feel right. I rechecked the output voltages: 24V dropped to 15V, 12V to 6V, and 5VSB to just 3.5V. It was clear that the low voltage was causing the indicator light to flicker and preventing the TV from booting up.
Since there were no schematic diagrams available, it was hard to tell if the issue was in the power supply or the mainboard. To test, I disconnected the power from the motherboard and used a light bulb as a load. I connected the 24V and 12V lines to the bulb and forced the power on. The bulb didn’t light up, and I only heard a "beep" from the power supply. At this point, I suspected the power chip might be faulty.
I turned off the power, discharged the filter capacitors, and removed the TEA1733P. After replacing it, I powered the unit again. This time, the bulbs lit up, and everything seemed to work. I restored the circuit and turned the TV on again. The indicator light stopped blinking, and a green light appeared. The backlight also came on, and I could hear the splash screen sound. The signal line showed normal video and audio output.
After the repair, I searched online for the power supply schematic of this TV and downloaded it. I shared it with others to help them with similar issues. Here are some photos of the process and the schematic file:
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