Make your circuit board with big ground copper. Use a 100nF cap. near each supply pin of an Ic. If there is a regulator ic ea LM7805 put near the input and output of this ic a cap of 330nF and an Elco of at least 10 to 100uF.
Make sure that the input wires and supply wires has a multiple windings trough a ringcore.
I hope you can understand what I mean, becouse I am not Englisch.