Hi, i've changed the power cable, the guitar and even the guitar lead and nothing makes a difference.
The only thing i can think of is that while i transported it in my car it got knocked in someway and it's dislodged something. Maybe a component from the power board or something that was loose and i made it worse.
It has small castor wheels and i 'pushed' it twenty yards across the car park so maybe the vibration highlighted a problem...
I think i'll check it into an amp repair place and see what the cost is to get it sorted. Hopefully it'll be minimal.