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genuine parts

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    A very typical failure of a very good lens – the Sony FE 90mm F2.8 G OSS: it’s no longer detected by the camera after a fall.

    Sony FE 90mm F2.8 G OSS repair and teardown

    This lens uses Sony’s proprietary focusing technology – Direct Drive Super Sonic Motor (aka DDSSM) – but with a twist: there are two such motors inside.

    Essentially, this motor type is an ultrasonic linear actuator, first introduced in exactly this form back in the Minolta/Sony A100, where it was used to move the sensor. The lens is moved along a straight shaft via micro-deformations transmitted through a piezocrystal. The waveform is shaped (a sawtooth pulse with a sharp drop) to allow the lens to move in both directions.

    And that’s where the reliability problem lies: the lens mass interacts with the motor, which is not a solid piece and is quite fragile. The motor can literally break – either at the joint between the shaft and the piezoceramic, or across the ceramic itself.

    And so this well-used lens clearly ended up in for repair after a fall.