nakamichi dr-1

I'm working on a Nakamichi DR-1, and as soon as you turn it on you get the "Err" message displayed. Also, the cassette door will not open. When you press eject it feels like it's jammed. I took it apart to replace the belts, that was my initial task, and put it all back together but the door...

So far I've heard : Capstan belt FRSP-9.6" and backtension belt: SCY3.2" Yet others have said 9.84" is correct which would be longer so less tension on the transport workings. I cannot find any definitive answer on it. Anyone have these decks that could help and possibly tell a source for...