F3 boots up but no picture

F3 working okay last night,but when I turned on this afternoon it went through the boot up process according to front display but after reaching 100 and Sepe appears on front display it should show the ***box logo screen but all I get is a blank TV screen no picture nothing I can select a channel and that shows also but No picture even trying to select the menu option nothing appears just a black TV screen any ideas as to what is wrong and can it be fixed

Quote from grouser

F3 working okay last night,but when I turned on this afternoon it went through the boot up process according to front display but after reaching 100 and Sepe appears on front display it should show the ***box logo screen but all I get is a blank TV screen no picture nothing I can select a channel and that shows also but No picture even trying to select the menu option nothing appears just a black TV screen any ideas as to what is wrong and can it be fixed

Sorted it myself,must have touched the format button on handset DOH!!!!!