Ferguson tx100 sound problem

[Fidelity 26]

Our 51A3 has developed a sound problem it has gone distorted and quite nearly no sound at all
Over the last few weeks it started to go distorted when on a higher volume so kept it what id say normal.Then the other day i went out while mum was watching it and when i returned there was no sound.I assumed it was on mute as her hearing aide loop takes the sound direct from the freeview box but that wasnt the case there was no sound but faint crackleing.

So any sugestions appreciated and most welcome before my bloke takes it away as he thinks its a big expensive job.
We have had to bow down to moden ways atm and i went out and got a 32" led tv as the other ferguson tx100 was not heating up possable resister problem so hes comeing back to do that one first.