PCB for worcester 35cdi mk2 rsf boiler?

Following the fault dianostics, given a fast flashing red lamp, on J flowchart in the owners manua (The fan not running) I checked the air pressure switch(open circuit) ok, and fan primary winding (100 & 50ohms)ok, checked for 240v at st1 on the PCB for both heating and HW call (no voltage detected), and as directed changed the PCB but the fault still persists.

Switched the boiler on and the fan ran momentarily, stopped and the red lamp again began blinking rapidly. I repeated the above test giving the same outcome. i.e. no closer to rectifying the problem. I subsequently contacted Worcester Technical and they pointed back to the PCB?

NB: Great care was taken to avoit static disruption when fitting the new PCB. Firstly, has anyone experience this type of fault; and secondly, has anyone fitted a new PCB for this boiler and found it to be faulty?