I just bought a T6600 and as soon as a take-up reel arrives I will check the status of the mechanics. I'm sure I'll be ordering the belts from Vintage-Electronics as well. Pinch roller and heads look to be in good condition at this point. I was surprised to find this unit has 6 belts, which seems like alot to me. Also, the right channel meter light is out, so I will order all new lights for the sake of it (four I believe). I am going to order a service manual and user manual shortly and I will scan them and provide them after they arrive. In the spirit of helping each other out, the first thing I will do is upload them to all the audio forums that have a manual repository. With all these various forum's resources that already have an excellent databases to download from, I'll be adding these so others don't have to spend $$ unnecessarily!
Update: manuals arrived, I just need to have them scanned. I will get to a scanner and have this done in the next week hopefully. I see that there are 6 belts due to this being a single motor machine. So far the unit does play in both directions and brakes nicely. There is a bit of slow starting depending on how much tape is being pulled for a given direction, so the belts will be ordered and will do an oiling at the strategic points. It's such a nicely kept unit that this is the least I can do. I wouldn't consider this a replacement for my turntable system by any means, but more of something fun I've never explored before.