Bush RF6694D TV Over-Underscan

Question

I bought this 18months ago and it seriously underscans (by 2" vertical and 2" horizontal). I noticed more since I can tranfer the pictures to my PC and can see what I am missing.

The "ticker" on BBCNews24 is unreadable. On SkyNews I can just about see it. I didn't realise I was missing so much as the side aswell until ITV News went widescreen and I couldn't even notice any difference.

There is no facility to change the settings from any of the on-screen menus. I presume there is a hidden "installer menu" somewhere>