Last week i assembled the kpa500 of oe6rdd when we transmit we hear a realy loud hum (50hz) in the rythm of the cw signals i have compared this with my own kpa-500 and there is no hum i have tried to loosen the big srew which holds the tranformer with no result any ideas ?? 73 Klaus OE6KYG KX1 244 K2 1331 K3 115