heatline c24 combi boiler?

the domestic hot water was only getting warm. there was an electrical hissing? noise and the printed cuicuit board blew the fuses the two glass 3.15 amp ones and shorted out the p.c.b. i have replaced the p.c.b with brand new one . the boiler fired up for about 2 mins then the thing blew the fuses again have put in new fuses and the boiler is making that same hissy noise , like it is ready to blow again i have turned off the power and do not know what to do next .

john ryding
October 2010