I am not certain to what extent it is common knowledge that Canon’s teleconverters (TC’s) can develop problems with their locking pins. Specifically, that the locking pin becomes “sticky” and does not always engage into the lens to which it is being attached. This past April, on Artie Morris’ Fort DeSoto, Florida IPT, one participant’s Canon DSLR and 1.4x TC fell off of his 500mm lens. The TC’s faulty locking pin, which never engaged into the 500mm lens, led a counter-clockwise turn of the camera and lens (via the lens’ tripod collar) to become a near disaster. Thanks to a flash cord attached to the camera’s hot shoe, the camera splashed in the salt water but bounced back up and later recovered–it was never wholly submerged.
Ever since that event, I’ve been far more aware of the condition of all of my Canon TC’s and extension tubes. I noticed shortly thereafter that my 1.4x II TC’s locking pin began to engage only half of the time. Pushing the lever forward would force it to work, but did not constitute a fix. Finally, I sent it to Canon Jamesburg at the very end of April and had it repaired for $70.00. However, the fix did not last!
This November at Bosque del Apache I noticed that the locking pin was developing the problem that Canon repaired at the end of the spring. It had been six months and three weeks: three weeks outside of Canon’s warranty on all repairs. The good news–and kudos to Canon–is that sending it in with a letter explaining the problem, and a copy of the dated invoice from the repair in April, led them to repair the TC free of charge.
Just let it serve as a warning: if anything is not working as it should, and it is of enough concern that you need to remind yourself whenever using it to exercise caution because it could break, just get it fixed! The last thing you want is to lose a $4000 camera body because you didn’t want to pay for a $70 repair.