Skyworth 32L01HM LCD TV (8M19 movement) one machine two disease maintenance - appliance repair

SMD Aluminum Electrolytic Capacitor

Single Chip Microcomputer STM32L151CCU6

Ceramic Chip Capacitor

Murata Surface Mount Capacitor

Filter 18.432M

I was working on a Skyworth 32L01HM LCD TV that had no power at all. The screen didn't light up, and there were no signs of life. After disassembling the unit, I checked the main fuse and found that the voltage on the large filter capacitor (380V) was normal. However, the power board only provided a 3.5V standby voltage instead of the expected 5V. All other output voltages were zero. Pressing the channel buttons or using the remote control had no effect.

Since the main power supply is controlled by both the standby power supply and the motherboard, I started by checking the standby power circuit. Removing the aluminum heat sink on the power board revealed a swollen electrolytic capacitor. I then tested the 5V output filter capacitor on the power supply circuit. It was rated at 10V 680μF. I replaced it with a 35V 1000μF capacitor, and the 5V voltage was restored. The standby red LED lit up, and pressing the channel key turned on the TV normally, displaying the logo.

After connecting a DVD signal, the TV displayed the image correctly, but the sound was very loud on one side while the other was normal. Even after unplugging the audio cable and leaving only the video line connected, the noise remained. The TDA8932BT amplifier was powered on and its pin voltages were mostly normal. However, when I touched the power amplifier block, it felt extremely hot, suggesting it might be damaged.

After checking online resources and data sheets, I found that the sound adjustment circuit in this model was prone to failure. It consisted of an L358 IC and surrounding RC components. Replacing the L385 chip didn’t help, so I inspected the nearby resistors. I discovered that resistor R455 was open-circuited. Its value should have been 33KΩ, but two regular resistors were used in series. Replacing them fixed the issue completely.

In this case, both resistors R455 and R459 were open circuits, causing the sound problem. The repair was successful, and the TV now functions properly. Here are some photos of the faulty components and the replacement process for reference.