If your 3RT841B is a purely mechanical contactor (no electronics), it has no firmware. This guide applies only to the electronic variants – check your exact part number suffix (e.g., 3RT841B-1A... or 3RT841B-2B...).
is a common motherboard used in various Smart LED TVs, including models from (e.g., T32RTL6000) and (e.g., 32HS301B). Firmware Update Guide for 3RT841B 3rt841b firmware upd