Hello Michael, Maybe I can help you here....
Could you please give the correct model, in the title it's FBT13-65 bud in the message it's FBT13-50.
If it's a -65, on the main printcard you have a blue colored switch RS1 it's normally pointed to 0. turn this witch the contact switch off to position 6. Turn the contact on, use the arrows of the display to change the language. Change the RS1 back to 0 and try again with starting up the truck. What's the error now? I guess you have a broken diode.
Regards
Marcb