my mk 809 III - wireless AP6210 - Hdmi IT66121FN , bougt in 2014-2015, was not used that much.
tried several roms, some with different partition sizes, resolution (720/1080) and overclocks.
i do not remember exactly what rom was flashed, but it was working, before it stopped displaying suddenly one day.
to check if it was not dead, i soldered to the console port (gnd, tx, rx)an ftdi usb cable.
using putty at 112500 speed, the system seem to boot.
i tried the following roms found on freaktab, without succeeding to get the hdmi to work.
from the consol i could list the wifi ssids on some roms, and windows explorer displaying the two storage (internal and external sd) volumes as when android device is connected to a pc via usb.
Geekbuying_TV BOX_RK3188T_Android 4.4_official_AP6210 -> sd volumes mounted on windows
MK809III_ update_dongle RK3188T 6210_3.1
MK809III_AP6210_LIGHT_720p -> flash fail
ncr19a_mk809
NHR_17_20131012 -> flash fail
smic717394_809III_1080p_V4.4.02_ROM V3
ncr_31_mk809III_kitkat
powered through dc port with its original power adapter 5v 2amps.
any idea of what is causing the hdmi to not output a signal (tested on 2 displays samsung and lg).
any specific or stock rom to flash.
thanks.
pictures of the device, and the refrence () of the serial interface attached.