Poor picture quality

[eddtheduck]

Hello,

I have a standard Samsung tv box and have noticed that some of the channel picture quality is very poor the channels mainly effected are:

E4
E4+1
SKY 1
Eurosport 1 and 2

I have changed the internal cable,
The engineer supplied white and i changed it to black
i bought the best i could find 6 pound a meter hopeing this would solve the problem but no joy.

A engineer came out and said they would'nt touch the box untill i changed the cable back to the original one.

I did this and they had a look and still no joy with the picture quality
they say it's OK

Any suggestions on what to do next?

Thanks

Edd