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
Is there a (amp) power supply or transformer near the tonearm? If so, move it.

secrely ground tonearm/turntable to pre-amp.

Change the order that things are plugged in to your outlet, power strip, or whatever.

Good luck.
could be a poor ground connection,
but make sure you check tonearm leads to phonostage to ensure that they're no near any AC lines.
Also, make sure your phono rig and leads are well away from anything with transformers in it, e.g. power amps
good luck!