Here is a closer shot of the top side belt residue.

The belts on the underside were also melting.

There was more belt residue under the big flywheel.

I use cotton swabs and Kimwipes with isopropyl alcohol to clean up the belt residue. It has to all be cleaned off because it is like sticky tar. You wouldn't want any possibility of that stuff getting on a tape.

Once everything was clean I put new lower belts on. I got this belt kit from Martin quite a while back intending to use it way before now...but time goes by fast.

Here is the new topside belt.

While I had the cassette deck opened up I cleaned off all dust and dirt that had built up and I installed a new drawer belt.

The next step was to re-assemble the Beocord to try it out with the new belts. It played great. I tried several cassettes over a couple of hours and they all played as I expected them to. I am not going to mess with any recapping of the Beocord at this point. I might revisit that later if other problems come up. However, I do have another Beocord 5000 of this same type I will be wanting to fix at some point.
When I finish recapping the Beomaster 5000 I will test out recording from the CD50 to this Beocord. For now though, I am putting the cover back on.

Good job on the cleaning, I was lucky not much cleaning to do, and the belt tracks looks OK to me, everybody else have these belt residues I never had a unit with "melted belts"