It may be time for the repair shop but I thought I'd try here first. I'm quite certain my 1200 has a grounding issue. If I touch the headshell with my fingers it creates a hum on the audio lines. This isn't a real problem when spinning but it seems to cause other problems. This could be a tonearm or grounding wire problem. However, I'm unsure of how to test either one. I don't want to go cracking open my 1200 without testing the ground or tonearm for problems.
Does someone know the quick answer to
a) How I can test the ground line is functioning correctly (I'm guessing a current test of some sort but I'm no engineer, I know the ground shouldn't carry any current normally so I'd have to test a difference value between the input and ground or something but I have no idea how)
b) Anyone know how I can test the tonearm for a short?
c) Anyone had similar problems? Not a full out grounding problem, but a short somewhere? Any suggestions?

If this was a full grounding problem I'd probably hear the hum all the time and I don't. Only when I become the path of least resistance as I touch the headshell.

Thanks very much.
Conrad D. Seaman