Zanussi ZCOF636X coffee machine tripping rcd?

Hi,
I've been offered a faulty ZCOF636X from a friend of mine. It's only a month old and he has got a replacement under warranty but they didn't bother to collect the old one! He said that when you turn it on, it trips the RCD on his "fuse box". I presume this is a fault with the transformer in the machine? Does anyone know if this is a common fault with this model or if it could be caused by something else (another short somewhere?) Also, if it is the transformer, any idea how much a replacement is likely to cost?

Thanks in advance,
Sam