Sony cassette decks use an electric motor to propel the tape through the player and across the tape heads that reproduce audio. The motor moves the tape gears and cogs with a rubber drive belt that rolls across the wheels with enough tension to rotate the mechanism. Drive belts can stretch and break in time, requiring replacement. With a replacement belt and screwdriver, the Sony cassette deck can be repaired and running in a few minutes.
Write down the Sony tape deck model number, located on the back panel near the connection jacks. This number will be needed to purchase a replacement belt.
Unplug the Sony tape deck from the electricity, then remove the screws from the top of the component and along the back edge to remove the cover.
Locate the rubber drive belt along the front left side of the Sony deck looking straight down into the component. The belt is black and rounded like a rubber band. Make a note of the belt path around the motor wheel to the driveshaft for the cogs that turn the two tape reels inside a cassette.
Remove the old belt by pulling gently to stretch the rubber so it can be lifted off the motor wheel and extracted from th component. If the old belt is broken, remove it with tweezers to avoid touching any electronic parts inside the deck.
Install the new belt over the motor wheel and driveshaft, stretching the belt gently to slip it into the grooves around the wheels on the motor and driveshaft. Each wheel resembles a pulley with a groove running around the circumference. The belt seats in the groove.
Remove all tools from the open tape deck and plug it into a wall outlet, then press the "Play" button to test the belt for proper movement. The right-hand cog for the cassette should rotate counter-clockwise. Press "Stop" then "Rewind" to verify that the left cog rotates clockwise.
Replace the cover and secure with the screws.
Unplug the tape deck from the electricity while working inside the component. The deck can be plugged in only to test the belt for proper installation. Remove fingers and tools from the component when testing belt operation.