Cassette tape players are temperamental because cassettes themselves are an old, largely dying breed of musical format. This does not mean that you should give up on the humble cassette, however, since it is still seen as a cool, retro format and is kept alive by enthusiasts across the globe. Still, with a diminishing popularity cassettes and their players are harder to get fixed, and repair at home, because there are less people who sell parts for them. However, there are some things you can do to maintain your cassette player's functionality.
Dip a cotton swab in some Anhydrous isopropyl alcohol and gently wipe the heads--the metal fixture that reads the tapes. Dry the heads with a clean, dry swab after.
Press "Play" on the cassette player and gently wipe the capstan--the metal spindle to the right of the tape head--up and down the shaft.
Rotate the pinch roller--the black rubber roller that guides the tape--with a rubbing alcohol-dampened cotton swab. Wipe the stationary plastic and metal guide posts.
Wipe all the parts you have cleaned with a dry, clean cotton swab.
Plug in and switch on the demagnetiser--which can be bought in an electronic store or over the Interent for under £6--away from any audio equipment. Slowly move the head of the demagnetiser towards the tape heads. Slowly move the demagnetiser back and forth over the tape heads, but don't let it touch them.
Pull the demagnetiser slowly away from the tape heads and switch off and unplug.
It's not unusual for tape players to have two capstans and pinch rollers, so be sure to look for a second set.
Make sure you do not turn on the demagnetiser around any other audio equipment.