I have replaced the belts on that type of tape deck a few times, my first time being on a Beocenter 8000 like yours, and again only recently on a Beocord 6500. The only useful video I found was this one – Bang & Olufsen Beocord 4500 Cassette deck trouble shooting and new belts.
The video doesn’t go into exact detail but it should help. The large belt is the difficult one, and it took me a few attempts to get it to loop around the small plastic wheel each time.
Note that there is another common fault with that type of tape deck which I also experienced on the Beocenter 8000. Dillen helped me solve that a couple of years ago, see this post for the solution, in case you encounter it – Beocenter 8000 tape deck clicking issue – BeoWorld Forum
For that clicking issue, I used a shaving of plastic which was probably only about 0.25mm thick, and glued it on using plastic glue. I worked, and still works now.
Location: Liverpool
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