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Russell H.
Russell H., Technician
Category: Digital Cameras
Satisfied Customers: 12026
Experience:  Working with digital cameras & questions for nearly 8 years.
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i am looking for a service manual for the EF 300 F2.8 L USM

Customer Question

i am looking for a service manual for the EF 300 F2.8 L USM lens, as the manual focus function has failed and i need to understand how to repair the contact brush set
Submitted: 3 years ago.
Category: Digital Cameras
Expert:  Russell H. replied 3 years ago.
Hi, thank you for contacting My name is Russell. I will do my best to provide the right answer to your question.

Clean the contact set, by rubbing very gently with a clean dry lint-free non-woolen rag cloth. Clean both the contact set on the lens assembly (where it fits onto the camera) and on the camera body where corresponding contacts are on the lens mount.

After that... if the coating has not been worn off the brushes... I'm not sure that more can be done, aside from replacing a lot of the lens assembly piecemeal. Ditto for if the coating has been worn off the contacts/brushes: replacing that part of the lens assembly from some surplus or cheaply available 'junk' equivalent for sale 'for parts' or as-is/broken on or or, would be necessary. The part to repalce with would of course be the part with the contacts/brushes.
Customer: replied 3 years ago.
I have tried all of those sites again without any success, but will keep looking
Expert:  Russell H. replied 3 years ago.
OK. Let me know if I can provide any further advice about this matter.