Help setting up JMW tone arm

I actually have a JMW9 setup question, and instead of starting another thread I thought I'd tack it onto this one. I recently set up a JMW9 on a Scoutmaster too, and the other day it started having strange grounding problems. The arm hums when I touch it, and more distractingly, makes loud "thud" noises when I put it down on a record (sometimes even when it's not playing). Would anyone happen to know what's causing this? Thanks in advance.

Not having a JMW 9, I can only offer my generic response, which is that it sounds like either (1) something went wrong with your cartridge internally, or (2) one of your tonearm cables has suffered a short to your arm tube.

To check #2, I would visually inspect the tonearm cabling between the cartridge and the tonearm, to make sure there is no inadvertant metal to metal contact. Also, I would wiggle the tonearm cable at the back of the tonearm (the one that supplies the antiskating compensation), while holding onto the arm so as to generate the hum you described. If the wiggling of the cable causes the hum to disappear and reappear, then there may be something wrong with that cable or its connectors.

To check #1, I would switch cartridges, if possible. If the problems go away after you switch to another cartridge, be sure to switch back to see if the problems return. (If the problems don't return, then maybe the cartridge is OK, and it was just a matter of a tonearm cable shorting out somewhere.) Good luck.

Thanks for the advice. I've switched up the cartridges and the problem has disappeared. So it looks like it's the cartridge. I'l try re-installing it and see what happens.