The record deck is known as a PS-LK47P.
If you wish, another deck will work as long as it has a magnetic cartridge and no preamp built in.
A Technics SL-1200 is the sort that is fine and a definate upgrade.
Question edited for 'make model (what it is)', full model helps!
Usually sticky or dirty buttons. Wipe with a damp soapy cloth then dry. Lie it on its back and spray the buttons with electrical switch cleaner so it floods in behind the button whilst pressing them. Wait a few hours and try it.
https://www.google.com/search?q=sony+mhc+buttons+not+working
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