After many years the rubber belts disintegrated into a sticky gooey tar. This goo sticks to everything (especially fingers and skin) and needs to be cleaned off.
Opening the cassette deck was super easy. Six screws on the top case and it lifts off. However, getting to the belts isn’t easy. I had to remove a bracket on the cassette player which held in the flywheel. The screws were very tight and there wasn’t much room so I used the flex extension out of my Pro Tech Toolkit. I think this is one of the only times I’ve ever used it. Eventually I got it off and started cleaning up the goo. Isopropyl alcohol works miracles on this stuff and makes cleanup super easy. You just have to use a lot of it. After I got all the goo off, placing the replacement belts onto the flywheel was easy. Finally reinstalling the bracket I tested my Christmas song cassette tape and was delighted to hear jingle bells playing clearly.
Wear gloves when cleaning up old rubber belt tar. Seriously, this stuff was stuck under my nails for a week! Take plenty of photos and videos if you’re disassembling something for the first time. They are a great reference to look back on during reassembly or if you’re not sure where something goes.