Today was the first day that i had the time to turn on the Radar that came with the boat when i bought it.. ..It is a 1985 Si-Tex Marine Radar ..Model T-100 .. i turned it to SB ( preheating ) and waited a few minutes than turned it to ON......Nothing happened..the screen was blank.. According to the manual the radar should of started transmitting. Is there another key(s) to bring a picture to the screen..........What i wanted to know is....if the radar is un-operable how do i remove the radar dome , is there going to be a big hole there . Also does the boats' engine have to be running or will the radar operate just off the batteries.Thanks Tug