What materials are the original platter made from? It could be that the old platter was shielding the cart from the TT motor or some other source of electronic hum and that the new acrylic platter isn't providing the same shielding.
Just a guess, but I've found that my Rega table hums--with volume cranked all the way and needle above the record--when it is located above my amp. Moving it to a table beside the amp eliminated the hum completely, so it was definitely not motor hum in my case.
Just a guess, but I've found that my Rega table hums--with volume cranked all the way and needle above the record--when it is located above my amp. Moving it to a table beside the amp eliminated the hum completely, so it was definitely not motor hum in my case.