Canon Perfect Binder A1 Troubleshooting Manual page 135

2-36) Remove the e-ring [1] from the Shutter unit and replace the Hook arm [2] with the new type Hook arm.
[CAUTION]: Do not misplace the e-ring [1] or the torsion spring [3].
2-37) Reassemble the parts in the reverse order from the step 2-35).
2-38) Perform the check of fracture of the Hook arm in the step 1) to verify all is fine.
[Countermeasure cut-in serial numbers in factory]
Perfect Binder-A1 US WVL00010
Perfect Binder-A1 EU MVM00072
Perfect Binder-B1 US CVZ00172
Perfect Binder-B1 EU GZK00064
Perfect Binder-C1 US EGX20504
Perfect Binder-C1 EU EGZ20524
Perfect Binder-D1 US QWS00001
Perfect Binder-D1 EU QWT00001
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