Sony TC-40 Drive Belts

The Sony TC-40 cassette recorder uses two drive belts in the tape transport mechanism. The main belt, which drives the two flywheels, should be 190 mm in circumference. The secondary belt should be 100 mm in circumference. The thickness of both belts is approximately 1.2 mm in cross-section.

Before fitting the new belts, it is best to remove any rubber residue and clean the pulleys and flywheels. The original belts had stretched and were deformed, so I had to find suitable new ones that had a good chance of working.

The tape transport mechanism is interesting as it has two large flywheels. The primary flywheel is for rotating the capstan, and the main drive belt goes around this wheel transferring maximum drive torque. However, notice that the main drive belt also touches the secondary flywheel by a small arc because here, much less drive torque is required. This secondary flywheel then transfers its drive to another small pulley via the secondary (smaller) belt. This part of the drive is responsible for rotating the tape-winding spindle through the clutch mechanism.

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