Ideal isar he24 no hot water/heating 2nd problem in 1 wk?

Our boiler first started making vibration noises sporadically then came up with L9 fault code flame detection, engineer examined and replaced gas valve, all worked well for 1 week and yesterday noises stared again and today display showed as normal but boiler not working at all even when reset button pushed. Now display has gone completely blank? Help i know engineer will say pcb needs replacing but will this sort out the problem i have a feeling theres an original problem that keeps causes the others?

Andy
January 2010