Blank screen when tv switched on -audio only

Question

hi
i have a dual drf 2810 colour television reciever.

My tv is not working properly, the tv is switched on. then a blank
(black) screen appears with audio until a few hours later the picture
appears slowly from a blurry image to a sharpened one.

which part needs repalcing and is it a diy task?

i have already had a memory frame replaced last year.
thanks