[Coco] Dead Coco

[Fred D. Provoncha]

     Hi all,
This should be a simple one for you. I'm sure you've seen this before. I recently moved, and going through some old boxes of stuff I found an old spare Coco that probably hasn't worked since the early '90's. It's a Coco3, and I hooked it up to an old TV and turned it on and sure enough, as I remembered, it's got a problem. It powers up, but I get a completely blank green screen. I try inserting some cartridges, but it doesn't matter, I still get the same green screen.
Any ideas as to what is wrong?
Fred ProvonchaStansbury Park, UT