Nearby lightning could damage a multiswitch or launch Amp by entering its aerial input. Other than that, the usual failure is that of power supply capacitors, which are easy to replace.

I would think that someone like Michael Dranfield could take a look inside for you and see if there's an obvious problem:
TV, VCR and Digibox (Satellite receiver) repairs, spares, sales - UK service

If you fancy DIY, you'll find capacitor information here:
Television computer Audiophile Capacitors