Hi all: I am 15 years old, and have always had a knack for old audio equipment, especially boomboxes. I love fixing broken units, and have fixed broken cassette players and CD lenses. I'm the type of person that goes to the local thrift shop every week or so to check if they have any new units worth buying. My first serious unit was a Fisher PH-W1000 that I picked up at a thrift shop for 3 dollars, and I still get use out of it to this day. I also have some other portable shelf units such as the Sony CFD-Z110 and the Hitachi TRK-W550E I'm currently using the JVC MX-G50 as my main stereo system, and and the "Hyper Woofers" really kick! (It really makes the oldies music such as Sinatra sound nice!) That's a general overview about me. Feel free to ask any questions you might have!
Hi and welcome to the forum, @bass box ! Fixing vintage audio equipment is always fun ! I'm into repairing as well, just focused more on portable devices like walkmans more than on boomboxes.
I enjoy fixing them more than I enjoy listening to them and buying them! You're absolutely right, most of the rubber belts have stretched and decayed over time with good use. However, I still have some Sony portable boomboxes and a Panasonic Walkman with not-previously-serviced tape players that work fine. I've had to resolder a head to the amplifier board as well.
I've spent a good deal of time working on boomboxes, the only Walkman I've ever taken a good look at was my Aiwa TX406.
Great skills for a young user, you'll get better at it and before you know it people will want you to fix everything.