Tandbergs sound wonderful, even the really old ones. I have repaired either this model or one very similar to it. You thought the Sony was complicated inside? wait till you take a gander at this one. certain parts of the mechanism are pretty straight forward, other parts look like a Rube Goldberg nightmare. Don't know who Rube Goldberg was?
http://en.wikipedia.org/wiki/Rube_Goldberg
Parts for Tandberg are absolutely non - available. However, if you should need stuff like transistors and belts, generic substitutes are available. If the pinchroller turns out to be bad (on inspection it should be dull black, not shiny, and resilient, but not hard or sticky) Terry Witt rebuilds them for $40 including shipping.
All that said, this model is very reliable, and most times just needs a belt. The belt is a round rubber belt, and you can get them at
www.beltsforanything.com
If you do replace the belt, and it isn't broken, make a drawing of how it is connected, before you remove it. Trust me, you'll save yourself a lot of head scratching. If it works when you get it, open the top panel and take a picture. You'll thank me later.