thompson hd box

[green15]

hi to all hope u can help me i have sky hd box and just recently the box has developed a fault where some channels are breaking up and when u look at the info fault it comes up for information the code reads 28 and some times it reads 25. i have done all the checks signal to both inputs are fine and the odd time input 2 dosent lock i have had the dish realighned so the signal is coming through the lnb i have contacted sky and as usal they want 65 quid to send somebody round. i have moved the dual sat cable from port to port so its looking like the box could be at fault, is there a way to check out other tips to sort this out or can u get parts from any were i am up for taking the box apart not shy in having a go, thanks to all who get in touch.