I bought a Technika LCD 19B-M3 about 4 years ago to use on my narrowboat. This set has never been used and never been on the boat , I`ve only just taken it out of the box today, (been renovating said boat)..I`ve plugged it in and connected it up to the aerial that I use in the house to try it out before taking to the boat. All that comes up on the screen is NO SIGNAL.... any ideas please