Hum after replacing tonearm cable

I hope your phono cable is shielded?

Simple tests:

1) Disconnect tonearm ground wire from the phono stage and listen.

2) Connect additional ground wire with stripped ends from your phono groung plug to tonearm metal part and listen.

If the hum is gone let us know is it 1 or 2 or nothing.

1. Disconnecting tonearm ground wire from the phono stage did not make even a bit of the difference. With or without the tonearm ground wire bolted to the Ground Post of the phono stage makes no perceivalbe difference in anything. I wonder if this a Ground post or a tonearm ground wire that doesn't ground at all. Should be any hearable difference in hum when we connect/disconnect the tonearm ground wire?

2. The tonearm is SME 4. It looks silverfish plastic (I think it is painted magnesium). I guess I should be able to connect a ground to it safely... Thank you for your suggestions!  

Check the new cable continuity with a voltmeter?

Where is the Turntable plugged into?

What happens if you swap back the old cable?

G