For the test, I will update the TP-Link TL-WR840N V1 with firmware 13xxxx RU.
1) Let’s look at the revision of the router, in my case it’s V1, and it’s for it that we download the archive with the new firmware from the official site:
https://www.tp-link.com/us/download/TL-WR840N.html
In my case, the last firmware for V1 was TL-WR840N_V1_151023_EN. If you download the firmware from an incorrect revision, you can damage the router. Unpack from the downloaded archive firmware file.
2) Open the router settings by typing in the browser address http://192.168.0.1 and enter login – admin, password – admin.
3) In the menu, select “System Tools” – “Firmware Update”, click the “Browse …” button and select the previously unpacked firmware file from the archive. Next, click the “Update” button and wait until the firmware is loaded into the router and it will reboot.
At the time of upgrade, you can not turn off the power of the router.
After updating the firmware, the settings in the router are not reset.