Bought myself a fancy disco deck recently. Pleased with it so far but for a bit of hum when the volume is jacked up. Previous turntable was quieter in this respect.
If I remove the headshell, the hum disappears and I am left with just a quiet hiss.
I have a Nagaoka MP-500 cartridge fitted with nylon washers between the cartridge screws and the headshell. The ground wire is connected from the turntable to the phono stage.
Does anyone have any suggestions on how I might determine the root cause?
Does it hum more with the arm closer to the centre?
Try removing the ground wire between the TT and p’stage.
No
Then I get a very loud hum.
Smash it with hammers.
Mine does that if I tighten the thing that holds the headshell on, absolutely to the max. If I unscrew it, very slightly, but not enough to actually loosen the headshell, the hum vanishes.
Or earth the arm, and check earth continuity to the cartridge.
Will try that later 
The design Is tried / tested . There is a lack of continuity somewhere -cart tags are good? Check Pins in arm end for spring back . try earthing the phono stage or connect the arm lead earth to the amp earth ,or try all points via a long wire direct to the earth pin of the mains plug itself. Are inter connect leads one way with Directional earthing ?
Can be a pain chasing hum . Good luck .
So, it turns out not to be the headshell, the cartridge, the arm, the turntable or the RCA connections.
The noise is introduced when I include the Jolida JD9 in the equation. Connecting the turntable directly to the onboard phono on my pre-amp and the hum disappears.
Now, my perception is that this hum is louder with the SL-1200 than it was with the predecessor. Perhaps I am wrong. I cannot be bothered to get the old deck out as it is safely stored away pending a possible classifieds advert.
I suppose I should open up the Jolida and see if I can spot anything awry. Could it be one of the tubes? An electrical engineer I am not…
If I was to want someone to look over it, does anybody have a recommended tinkerer?
Want to borrow my SL1200 fine-tuning kit?
The Persuaders…
I’ll be opening up the phono stage tomorrow with one of these
Attaboy! 
I am upset ! ( a bit )
But
Less so lately having actually heard rubber band things trying to render real piano ( at equivalent budget) which techy delivers so easily.
£3,000? (Which is what a boggo SL1210 now costs)
This is rong.
The Boggo ones cost £1300.
Bargain!
Not if you take account of the evo profit markup. Fucking dealerscum 
