Dual CS508 generates hum

Decided to pull some equipment out of storage. Had an old NAD 302 amp in great condition along with some PSB speakers. Connected my ipod and the sound was so beautifully warm. Decided to connect my Dual CS 508 turntable with a Grado cartridge and everytime I went to play anything I got a hum out of one channel. Thought it was amp but tape deck works fine, tuner or ipod but for some reason this turntable produces a hum which i don't recall (it has been years since it was used) I made sure it was grounded and it was. I tried connecting the turntable to my Mac to transfer some LPs to my computer and I received the same hum. Anything I can troubleshoot? I was thinking of picking up another cartridge to see if it is the Grado. I got rid of most of my records, but have a small selection that I want to put on computer.

If its only humming in one channel, and when you reverse the IC's from pos to neg & visa versa the hum follows the change from channel to channel the problem is either in the IC's or quite probably a loose connector attached to the cartridge pins/phono wire. Check all four pins to insure that they are tightly connected to the phono wire and see if that helps.
Agree it is a loose, corroded, or grounded wire inside the TT's connections or connectors.
The wires going to the cartridge are quite snug, pulled them off and reseated them, I will probably change the interconnects and see what happens.

Let me ask another question, which is better to do a splice of the interconnectors, or open the turntable up and remove them completely from the turntable and put some new ones on?