micro genus 23mffi boiler. 7 year old been exellent?

now pcb transformer burnt out ,obviously an external fault somewhere in the boiler .but a heating company cannot tell us what part has gone,to replace it .they just say you have to buy new boiler.fair enough but whats the fault, does anyone know of a common fault. i am paying insurance cover for this and i feel i am being robbed,i will still buy a new micro boiler,very good. but dont like being ripped off.