DIBOSS tv shows no picture

Question

My tv does not show a picture (black picture only, sound works fine) however when you step through the AV channnels, etc and get back to the tv screen the picture does appear for 2 seconds and then goes black, (so it doesn't seem to be a problem with the display but the signal link to the display??). It did correct itself recently for about 20 minutes but went black again.

Regards
Iain B