have you changed the ch thermister? maybe it's going faulty
and allowing the boiler to overheat intermittantly (not an expensive part) can't see it being pcb related, but then again many a pcb has brought me on a wild goose chase in the past
but can't see you haveing the same issue with 2 pcbs
what are the a) system cold pressure b) system hot pressure
T
June 2008