how can a newby clear tonearm hum?

i rewired a hadcock gh230 arm that came w/ unusable cable. it sits on an oracle 1 w/ a aurum beta s. in a spare tonearm, there is no hum from the cartridge or table.i ran a silver ground wire from the cartridge to the din plug which reduced but did not resolve the hum(which is probably inaudible over music, but then i'm pretty excited & so perhaps less than critical right now). i also wired the din plug myself( i view this as a learning opportunity) but i suspect that my problem is in the ground wire or center pin of the din. any ideas? thanks