Aiwa CSD-A100 and other cassette recorder repair kit

I found this cassette recorder in a local trash :-) It suffered from the rain and dirt, but the average condition was 4+ star, so I decided that it could be still alive. I took it to home and disassembled it. The antenna was broken - only a couple of radio channels worked. The tape did not play at all, but the CD worked! I decided to repair it. Not that I really need it, but I still have some old tapes and CDs, so if this device can play them, why not to listen to them again and remember the times when I was young...

I disassembled it and found that the motor belt turned into something resembling grease for bearings. I removed it with isopropyl alcohol. I printed a new belt with TPU. It kind of worked, but the playback speed was slower than required. I found that the TPU belt does not provide as much friction with the motor shaft as the rubber belt does, it is too slippery. Unfortunately, I don't have true rubber filament. I tried various belt diameters shapes with little luck - they work fine while they are new, but after 1-2 days they get stretched and the friction becomes not enough. But finally and I found a working solution: smudge the TPU belt with rubber glue and let it dry. The glue will make a kind of thin rubber cover over the TPU and it will make the same friction as the rubber belt does. You can use a match or a toothstick to apply the glue over the inner surface of the belt and let it dry for 10-20 minutes. I tested it with a stopwatch and the song timing with TPU+glue is correct even after many days!

Print settings: use CURA for slicing, it slices better. Set layer height = 0.1mm, and wall transitioning threshold angle = 45, and speed = 30 mm/s. Other slicers and other settings may result in very low quality of the belt.

Another problem was that the rewind button did not work - it unpressed immediately. I tried to understand how it worked and found that there is a piece of plastic that is responsible to stop the motor when the tape is blocked (i.e. end of the tape). This piece of plastic had a little broken pin, so it stopped the motor when it didn't have to. I made an enforced copy of this part in FreeCAD, printed it using PETG and now it works as it should. You only need it if you have any autostop issues.

So, finally, I cleaned it and assembled it, and it works fine - both CDs and tapes work. I only need to find a new antenna for the radio to work well.

PS: I know, there is a very little chance that you will find Aiwa CSD-A100 in a local garbage dump, but you can use the same approach to repair any other model of the cassette recorders! The belts are most likely to blame if they don't work. I have 2 other Panasonic recorders that don't work. One was bought in 1990s and another, almost the same model, was found recently in a local trash, I took it to repair my old one, but it turned out that both have the same belt issues and I'm gonna print new belts for them...