My Ferroli Optima Boiler struggles to ignite due to a buzzing/chattering Relay. Apparently this is a fairly common fault and a new PCB costs about £180. The chattering Relay is the one to the far right of the PCB and often looks burnt due to the sparks caused as it chatters. After much searching and testing I've managed to cure this fault for about £6. The chattering relay is actually caused by a breakdown in the small blue capacitor located close to it. This can be replaced for about 20p with a 10uF 100v (or bigger) electrolytic Cap. Don't worry if the replacement is physically bigger, just bend the legs. This may cure the fault; if not and the relay's knackered, replace the relay with a 48vDC 8A double pole one. The SCHRACK original seems difficult to locate in the UK but I got a similar spec one off ebay for £5 and it works great. Thanks to Mr Bardwell on Abbeydale Rd Sheffield & Hartley Electrical Repairs on London Rd Sheffield for diagnosing the capacitor as the cause of the problem. Saved me £'s!