[Bob Andersen]

That's a nice looking Tandem you have I used "Orange Goop" hand cleaner on the cable. I expect GoJo would also work well.
I used Novus #2 plastic polish on the screen. It works well on scuffs. That's the first time I've seen the cable coiled on the back of the tube. Might be better to uncoil a little and let it rest on the floor.

Good luck. These are not easy sets to repair and maintain.