Canon EF 35-80mm III Teardown

Written By: Lawrence Lau
Published: 24/11/16
  • Comments: 3

Canon EF 35-80mm III Teardown

Published: 24/11/16

Teardown

Introduction

This guide shows how I disassembled the lens in an attempt to clean it.

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    • The glue is quite sticky - the sticker ring will never look the same again.

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    • Unscrew the 3 screws that hold the front lens assembly to the rest of the lens.

    • It seems this partially disassembled lens can be used as a macro lens - I didn't try.

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    • Remove the rubber ring. This exposes the 3 screws and their metal collars.

    • Take care not to drop the metal collars - they are like washers.

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    • Pull out the connector of the flex cable vertically while supporting the circuit board (I used a plastic spudger to push down the circuit while pulling the white connector). To insert it back, simply push it back into the slot. Note the orientation of the connector (Take lots of pictures)

    • Note the black plastic pillar - the white focusing gear (obstructed in this shot) from the focusing ring needs to go back inside this during re-assembly. It's a little tricky.

    If you turn the focusing post circled in blue, and the gear under the motor doesn't spin freely then you have to undo the two screws on the focus assembly, pull it out, and undo the two screws on the motor mount. There is a pulley under the motor, and a rubber belt that attaches to the pulley/gear. Note these screws are different lengths than the other silver screws in the lens. The short ones hold the motor mount, and the long ones secure the focus assembly. The rubber belt in the photo is not at 45 degrees, this belt is off the pulley in the photo. The pulley and top of the pinion gear are V surfaces. If the lens element was out of the track, and floating inside the lens, someone turning the zoom ring has gotten the belt out of place too. Holding the motor assembly upside down and placing the gear in the motor bracket hole, and using a small screwdriver to get the belt on the pulley is a frustrating but necessary experience.

    JimC -

    Place the barrel with the inner optic assembly on an optical grade cloth to raise it about 1 cm, then align the focus post with the white shaft and get the two guide keys to slide between the barrel and the lens element. Good luck.

    JimC -

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    • Unscrew the 3 screws to release the barrel.

    • Be careful not to damage the metal brush. It can be removed and re-installed easily.

    If the lens element is off the track, remove the brush and reinstall the lens element in the track. Don't touch the red circled screws, no need to. Reinstall the brush. This photo has the correct orientation if you didn't shoot your own photos.

    JimC -

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    • Once the barrel is freed, the rest of the assembly comes apart once the pieces are rotated - they are 'nested' within helical tracks inside each 'shell'

    • Before you disassemble it, note carefully how each 'layer' is nested within the next one. Otherwise it will take a lot of trial-and-error to put it back.

    • The focussing ring assembly also 'drops out'. To re-assembleit, align the 3 tabs in the barrel with the slots in the inner helicoid (inner part of the focussing ring), then turn it 45º.

    • During re-assembly, ensure that: 1. the ribbon cable doesn't get snagged. 2. the white focusing gear needs to sit into the black pillar (highlighted in step 4)

    • Useful document: Parts Catalog for Canon EF 35-80mm III Lens

Author

Lawrence Lau

Member since: 24/04/12

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