Biasi riva advance he help needed.

[umer]

Hi, I have a riva advance he almost 10 years old. Couple of days ago house electricity tripped at mains and after resetting every thing was working but boiler. A 3.14 fuse was blown on pcb. I replaced the fuse and with help from older posts here checked that pump is failing to start thus boiler is going to lockdown after couple of sec of tuc, tuc, sound. I replaced the pump with new and now the pump starts as soon as boiler is switched on with out any demand and after a sec boiler locks with a constant red and left green flashing. Pump still keeps running. After further checks I found out if I remove the micro switch (the one in transparent casing) than the boiler doesn't locks down but pumps keep running with out demand. Now if I turn hot water on creating a demand and than manually engages the switch than burner turns on. Now if I put the switch back in its place, the burner keeps running as long as the water is running. As soon as the water is turned of, the boiler goes in lockdown again.
Is it safe to assume that pcb needs replacing? Is it worth doing it on 10 years old biasi? I am already 70 pounds in by replacing the pump.
Any help will be greatly appreciated.

 

[umer]

One more observation, if I start the hot water before turning boiler on than boiler still go to lockout. Only if I remove the micro switch and than turn on the boiler, turn water on, push the switch manually than only burner starts and hot water comes.