I just bought an MHL adapter for my Nexus 4. I have connected the adapter with a HDMI cable to the TV, plugged the microUSB into my phone and provided power on the other microUSB input as I should.
The TV showed an error message:
Check signal cable +some small text about possible power and source problems
If I unplugged the power from the adapter, or disconnected the HDMI cable, it said:
So I think I was on the right source. I tried a different HDMI cable, another HDMI port on the TV, and another phone (Samsung S4), but the TV still showed the error message. It seems to me the phone did not give a signal through the microUSB port. Is there something I should turn on?