So I decided to swap a few carts around on the weekend, and once I'd managed to include spacers, have the screws working etc. connected up the MC cart to the TD 160 mk1. What I had forgotten is that in the absence of a ground wire (the way Thorens made them), any slightly less than perfect contact (e.g.. on one of the 4 pins to the cart) makes a hum. I went through a few possible issues and eventually tightened the connections up a bit last night and managed to get it to a minimum (I removed the earth from the plug into the multi block so that ground loops are minimised (before doing this it was ridiculous), but think it could be improved by a good clean of all the contacts. Any recommended contact cleaners that anyone uses? And where to buy - presumably an electronics shop would be an idea?
Anything else I should look at would also be good advice (I lined up the cart, made sure of the horizontal and vertical alignment then used a protractor to make sure it sat properly in the grooves so it sounds fine, just that little bit of hum)