Hum after replacing tonearm cable

Thank you for your considerations! Exposing the ground cable wire and connecting it to the phono stage grounding pole fixed the hum issue. It now performs as expected. 

Check the continuity of the turntable ground wire. Secondly make sure that the ground termination makes it to the tonearm. An SME 3009 tonearm as an example is mounted on rubber grommets. If the cable ground is terminated at the chassis it may never make a physical connection with the tonearm. Another interesting issue is if the tonearm wires employ the use of Litz wire where the strands are individually insulated. If so the insulation has to be scraped off before soldering.

Just sayin,
Starwarrior
Thorens Td124/Mac Ma275/Mac C2700/Manley Massive Passive/Brennan B2

In external phono cable, especially  used one, the problem can occur in the soldering joints, it can be inside RCA or DIN, each connector can be inspected and re-soldered. 

That would work fine.

The cable that hums is used. It was purchased on Ebay. The issue turns to be behind the broken ground wire. There is a crack right where it meets the spate connector. I wonder if it would be OK to just detach the spade connector from the ground wire, open the wire insulation at the end and wrap the exposed ground wire around the Ground Post of the phono stage? Would it be any side effects in exposing the ground wire or it has to be terminated by spade connector?

I thought you arm was rewired internally too. 
Or you are talking about external cable only? 

You need a meter to figure this out. I suspect signal negatives are being shorted to tonearm ground. Some tonearms do this. Check ground continuity of the cable. It should be isolated from the signal negatives. Do the same at the tonearm. If the tonearm is in reality a 3 wire arm then you will have to use the old cable or do significant surgery to the new one. 

put the old cable back on. problem gone? then it's the new cable.

if hum with old cable, then it's not the new cable, something got disturbed, 

Din connector? RCA termination block? Tonearm wiring? 

hum in both channels is a hint.

what do you mean by high-end cable?

I suspect it is not 100% compatible or the new cable you bought has a design defect. If possible, switch back to the original cable and test it. Then power down (for about 5 minutes) and test the new cable. This is so you can figure out if there is intermittent failure or consistent failure in the new cable.

At any rate, you could always flag to the manufacturer and get your money back.

What happens if you swap back the old cable?

G

Where is the Turntable plugged into?

Check the new cable continuity with a voltmeter?

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!  

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.