Well, I have attempted to clean every square inch of this 5200. I lubed the power switch and it appears to have fixed the "stickiness" problem. I had a broken OEM coax connector which I cutoff and replaced. The video cable connector was not making a taut connection to the TV switch box so I simply bent one of the "prongs" (for lack of the technical term that escapes me) inward a tad to fix that. I used air cans (plural) and alcohol to clean this thing up. These were obviously all easy fixes that a caveman could do. I was pleasantly surprised that I could get this thing working at all.
Here are the outstanding issues I have:
The system came without joysticks, so that is on my list.
The metal covering around the motherboard has rusted. I have contacted Best Electronics to see if they have this part along with joysticks for this system.
There is also a brown staining all around the inside and outside of the case which I believe has to be from cigarette smoke but coincidentally it is similar in color to the rust. I've never heard of "rust" spores making homes in plastic crevices so I have dismissed that.
In any event, the rubbing alcohol did a fair job in getting rid of the brown staining in spots. Are there suggestions for any other cleaners that may do a better job?
Incidentally, the track ball controller does not work. But, for 20 bucks, I have a working 5200 with 7 carts.