I have an ideal mini c28 boiler which always works fine on hot water,but when in heating mode & ran for about an hour fails to light. The fan runs but i get no spark. The boiler fault diagnosis says no ignition signal from the full sequence ignition device. I found 3 dry joints on that pcb & re solderded. Fan operates correctly & air pressure switch tested ok. Is the pcb a common fault, has anyone had this fault before & the pcb fixed it?