Hi. Looking for advice for an ideal classic boiler . Its been fautless for years but has suddenly stopped. It wont fire up. Fan and all other faults ive read on here seem ok. However on looking at pcb jus before firing i can see blue flash in one of the diodes , so i take it i need a new pcb. Is this the cure or is there likely to be another fault thats caused it. Err , like boiling a kettle beneath it ! ( wasnt me )