Open the TV chassis and use a digital multimeter to check the main power rails on the RSAG7.820 board. Ensure stable 12V, 5V, and 3.3V deliveries. If these voltages ripple or drop, your issue is likely bad capacitors in the power supply section, not software.
Enter the update mode on the device by pressing a specific key or combination of keys during power-on. The specific key or combination of keys may vary depending on the device's model and version. rsag7820 firmware upd
Use a standard USB 2.0 or USB 3.0 flash drive that is 32GB or smaller in total capacity. Open the TV chassis and use a digital