Canon 400 F/2.8 IS - AF Problems

Hi

I tell you a problem with a 400 F/2.8 IS. Autofocus stopped working. Doing tests, I took out the screws on the focus distance selector and the autofocus worked again. Is there any explanation?

Something similar happened to me with a 300 F2.8 non IS, without screws in the focus distance selector the autofocus worked


Thanks for the help

I have both those lenses and never had any thing similar happen to mine. If you've half diagnosed the problem, I would send them off to an independent repair service and see if they can sort them.

If you took out the screws and it seemed to have fixed it, the old switches could possibly be failing. Mine stopped working so I took off the four screws on the lens mount and turned out the 7 or 8 wires were so thin, they broke off the contacts and I had to re-solder them. Thankfully back in shape. Almost had a heart attack.

Hi

Finally I took it to an alternative service, because the official services do not take it for its age. These service make adjustments to the focus motor, cleaning and lubrication. He also had to solder some wires. Now it works perfectly, without the need to change parts that are very difficult to find in my country.

Here are some photos taken during the repair process

emilianoluis wrote in post #19553361
Hi

Finally I took it to an alternative service, because the official services do not take it for its age. These service make adjustments to the focus motor, cleaning and lubrication. He also had to solder some wires. Now it works perfectly, without the need to change parts that are very difficult to find in my country.

Here are some photos taken during the repair process

Glad to hear that it's working perfectly. I hate getting rid of old lenses just because they need repair, when I think of the fine optics even in the older lenses, it goes against the graine.