Skyworth color TV 6D90 movement 29T61HT red light is not on the fault repair example - Appliances

Single chip microcomputer STM32L151CCU6

0805 red light LED patch light beads, 0805 red light highlight, 0805 LED patch hair

0603 red light factory direct sales

SMD aluminum electrolytic capacitor

During maintenance of the Skyworth color TV model 6D90, the 29T61HT unit showed no red light. The +B voltage was measured at around 40V. After disconnecting the standby control circuit, the voltage rose to 140V. The 5V power supply on the digital board was normal. Using an oscilloscope, the SDA and SCL signals from the memory were checked, but no data exchange waveform was observed during normal startup. Instead, a steady DC voltage of approximately 4.6V was displayed.

The analysis suggests that the issue lies with the digital board, possibly involving the memory, CPU, or the SDA/SCL data lines. Following the principle of starting with the easiest solutions first, the resistor connected to the LM1269 chip on the SDA/SCL line was disconnected. Upon booting, it became clear that the LM1269 was damaged.

It's worth noting that in typical cases, a failure in the CPU "plug-in" block affecting SDA/SCL would usually result in a "busy" state due to continuous data exchange. However, this case did not show such behavior, which makes the diagnosis more complex. Further testing may be required to confirm if other components are involved.