Main printed circuit board

we have just changed the ecu or main printed circuit board as u may call it! board on our zannussi fle 1416w as the washer stoped working and a cliking noise came from it so we took the old one out and found that were one of the plugs went was black as if blown we have just payed £90 for a new one and put it back to the washing machine plugged all the plugs back in the right places and wen we plugged the washing machine bk in the ecu board sparked and wen switched the washing machine then on with the on/off switch nothing came on aprt from the light on the on/off switch and the door light the cycle lights dint come on and the machine made a bleeping noise please can u help me wat did i do wrong or is something else making the the ecu board blow???