Turntable Hum

I've got an old Technics that is giving me fits...there's a slight hum present, that's there regardless of whethter the unit has a headshell attached or not, and regardless of whether it's AC power is plugged in. When I swing the arm across the platter, the hum varies from crackling and loud to nothing. It's not near a transformer or anything like that. Any ideas? I'm really perplexed by the behavior of the arm.
Has it ever behaved and if so, what change happened that initiated the problem?
do you have the TT grounded separately to the pre-amp?
No, I don't have two grounds run. I'll certainly try it, but I guess I ruled it out since the hum doesn't change when I unplug the unit.

We have a less-than-a-year old baby, so I'm not sure when the problem cropped up, since I don't get as much time as I used to. I'd love to be able to trace it to one event, but I can't.
Try turning the plug over at the wall socket.
Some turntables sing some hum, if they don't know the words...hmmmm
Could there be a problem internally with the arm wiring, it seems that a hum from a broken or bare wire might change it's sound when the arm is moved and changes position. Just a thought.
What cartridge are you using? If it happens to be a very high output cartridge like some Grados, they can cause hum.
I have a Stanton 500, a Shure m97xe, and a Shure v15VMR, and the hum is there on all of them...but it's also there without a headshell attached. I'm afraid it's the wiring in the tonearm as well, but I feel reasonably comfortable attempting to replace it. Is doing that something that will cause me to pull my hair out? It seems straghtforward enough.
Have the phonocable wires from the tt been moved? Are they passing near a power supply or ac power cord? Try moving and rerouting the phonocable wires.

Don't worry, buddy...We'll get you through this.
They come out of the turntable, which is mounted on the wall, through an opening in the back of the shelf, and connect directly into the preamp, which sits on a shelf underneath, crossing nothing. They haven't been moved in a year or more, but it could've been that I didn't notice the problem when I moved into my current location. But they're not original; they were replace by the former owner with something sturdier and heavier gauge, so maybe the connections are going.

I've may try wrapping the cables in foil temporarily to see if that kills the problem...at least that could narrow it down.

It sounds like the ground wire may have lost it's connection inside the arm or where it attaches to headshell or output cables. Do you get strong left and right output from the TT?
I had a situation where the clip was hanging by only aone or two strands of the arm wire. It happened to be a ground wire and there was a terrific hum. After re-soldering the clip to the wire, the hum disappeared.

Check all the tonearm wire connections!!

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!
I got into the turntable night before last and discovered that the prior owner's installation of the Ultralink cable had resulted in some circuit board trace destruction. I can't really solder to the next point as they're too close together. It's a stand alone circuit board, meant to be a bridge between the tonearm and RCA cables, and there is a short length of wire between the two.

What would you do? I'm tempted to A) strip the wires going to the tonearm base and solder the RCAs to that or 2) remove that wire altogether and solder directly onto the tonearm base. Would option 2 be the no-brainer?
A sounds like the best option.