I'm getting a lot of hum from my turntable. When I play with the cartridge wire connections nothing happens but playing with the connecting cables, especially near the amp terminal jacks aggravates & temporarily corrects the problem. The ground wire is securely connected. Could applying a bit of white lithium grease to the RCA cable plugs and the outside part of the amp jacks serve as a contact cleaner/enhancer and solve the problem? Is there something better to use? The other end of the cable goes directly into the turntable (no RCA plugs). If I could get a replacement cable how would I remove the old one and connect the replacement? Thanks.
Don't use lithium grease on a phono jack. If you want to increase conductivity, there are specific potions made just for that which are less likely to cause problems down the line. Try either Cramolin or DeOxit cleaner/contact enhancer.
Your problem is most likely to be defective cables exiting the Dual. It's possible the jacks are cold soldered inside the receiver, but unlikely. If you move the cable itself and not the RCA plug and the noise comes and goes, then you need new cables running from the table. Or cut the existing cable short and add new RCA's.
Some Duals also had RCA's on the underside of the plinth, most did not. Most were soldered in place. Unless you know how to solder well, this might be a job for a technician. The PVC insulation on the OEM Dual leads will melt rather quickly with too much heat. You can make more of a problem for yourself if you try to solder the connection and do a poor job.
Check a few threads in the archives which ask about Dual tables to find a Dual repair website. Then determine whether your problem exists in the cable, the RCA or the receiver.
There are no RCA's on the underside of the plinth; the cable is soldered inside. After manipulating the end of the cable where the RCA plugs that go into the amp are I've actually (probably temporarily) managed to eliminate the hum/feedback type noise. I don't think I'll be able to change that cable myself so I'll probably try the contact cleaner/enhancer first. Where would I find substitute RCA plugs if I wanted to try shortening the cable? Thanks.
I take it you don't know how to solder. There are solderless RCA's, Radio Shack sells a set. But they aren't the best idea for a phono lead due to the very low Voltage involved. You'll need some sharp, small cutters to strip the insulation off the Dual leads and, if you have no experience with this, it's sort of hard to think you'll do a good job considering the very small parts you'll be dealing with. Check with the shops dealing with DJ's and pro audio in your local area for someone who can replace the leads from the underside of the Dual. It's the right way to do the job.