I have 2 Aiwa cassette decks, see below.
Fault: Cassette has started to play very slowly. this unit has has good use and has not been used in the past 5 years.
AD-WX999 TWIN CASSETTE
Fault: Play does not engage. this deck has been in a box in my waredrobe for around 15 years, so its not had much use. I tried to play cassettes but it sometimes tries but mostly fails to engage the heads. Same for both decks A & B.
First their not worth fixing, and obsolete.
second you can take it all apart, clean and re-lube all the moving parts, replace all the drive belts, then they will probably work. But is it worth all the effort to find all the belts, and R&R all the moving parts? It's a major project to do all that work for an obsolete pair of machines. You really need to love cassettes to do all that.