If you happen to have one of these pieces of junk here is how you fix most problems. I was asked to fix one which the Digital Tuner stopped working. This is how i resolved. (Obviously check Ariel connections etc).
Perform an EPROM reset;
Ensure you are on Analogue TV
Press Display until a window opens titled Information
Press 1
Press 1
Press Line (at the top)
One after the other in sequence.
A box should open top left and audio will mute
Press down until EPROM is selected
Press right
A box will display showing Main Power Off
Turn the TV off at the mains
Wait 30 seconds
Turn the power back on.
The unit has now been factory reset and all interface cards reset. You will need to re-tune Analogue and Freeview/ DVB.
I hope this helps you. I took me ages to find this.