Turntable Hum

I'll let you all know as soon as I have time to check everything...so far it's not a loose clip or anything, and I'll report back when I've had the chance to devote myself more fully...

I've done a little searching around and discovered comments here and there regarding the change in capacitance that can occur with heavier RCA cables, which is what the prior owner of my deck put on...I'm not certain what the brand is and I'm not near the deck right now to look, but they're very thick cables with shielded plugs, and the cable itself is probably 75% longer than a standard table cable would be.

I'm starting to wonder if this could be where my problem is coming from, since otherwise it would appear to be in the tonearm wire. I haven't checked the solder connections for the RCAs yet, but I'm wondering if I should just replace the fancy cables with plain old RCAs when I do to see if it makes any difference.

Is there a hard and fast rule about what cables are usable with turntables?

Well, on a hunch last night I connected a second wire between my preamp and touched the other end to the pivot screw on the tonearm...hum gone! Now I've got to figure out how to permanently mount the second ground wire...

Did this hum get fixed?

Not quite - I still need to connect a second wire to ground the tonearm, and am feeling a little nervous about getting inside to do it, so I'm hoping there'll be an obvious place to connect it once inside. I have a young daughter, so I have to do this stuff when the opportunity arises!