I had the same problem with my 4 switch, It was the power supply. My advice just go up to your local hardware store and pick up a universal power adapter
I have had the worst luck tracking down a 7800 on ebay with the connections and at least 1 game but finally I got one, 33.00 for the console with 1 controller in the original box with joust. I should be coming in a couple of weeks
So what do you use? I just got my new switch box in the mail re-designed to fit todays televisions for 6 bucks works great and I dont have to disconnect my cable and at radio shack I payed 5 bucks for the coxial adapter and I have to disconnect my cable and switch off my cable box to switch games.
All I do is leave the cords pluged in, Put the controllers in the storage bay, and I leave the controller cords on the top of the console then I cover it with my dust cover