Thanks caperjack, when it first went off I was just on battery supply. I have tried to switch back on with mains supply and just battery, it just lights up briefly then goes off again. sorry i can,t be more technical
i would next try this ,remove Ram chips,and try booting ,if 2 ram chips put one back in and try turning it on ,if nothing remove it and try the other chip.
ram chips are found on the bottom and under a removal cover ,need a small screwdriver ,usually!