Use a USB 2.0 drive (8GB or 16GB) formatted to FAT32 .

Plug the TV back into the AC outlet while still holding the button.

To download the firmware for the mainboard specifically matched for the LC390TU1A panel, you can use specialized technician repositories like Receiver Pro or Software Zone .

The is a universal "three-in-one" motherboard commonly used in 32" to 40" LED/LCD TVs. Mainboard Model: TP.VST59S.PB801

Up to 1920x1080 (Full HD), though the LC390TU1A panel typically uses 1366x768 Panel Model: Panda LC390TU1A (39-inch Cell) Input Ports: HDMI, USB, VGA, AV, and RF (Tuner) Backlight Output: 45V–94V (approx. 45W) ⚡ Firmware Installation Guide