I have recently bought a Thomson TiVo from Currys. The serial number does not contain a numerical sequence anywhere in the range 6020 to 6023. However the third set of digits in the TIVO Service number is 601F. Presumably this makes it a very old machine. I am experiencing some crackling/Hissing on terrestrial sound - do I have a duff box? Would it better to to take it back and exchange for a newer model or seek the free repair. Any advice would be appreciated.