topic Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses) in EF & RF Lenses

Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

NirvanNa — Sat, 17 Oct 2020 20:29:30 GMT

Hi everyone, opening this topic asking for Help, for my 100-400mm canon mk1 diagnoses the AF Problem.

I give some time for a dissembly the lens, and i confirm, there is not any residual rusty in the PCB connectors our some flat cables damage.

Like is says, the AF mode dont turn on and i notice those things:

the IS Works on camera

The botton AF/MF dont siwtch on camera (ony MF)

When i use the manual focus and do Half focus Botton, i have the confirmation focus Point, but no Auto focus

Waht to you think?

IT is a USM MOTOR our Pcb bionet problem?

our usm motor

[Links removed per forum guidelines. Images from linked pages added to facilitate discussion.]

thanks guys

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

shadowsports — Sun, 18 Oct 2020 02:19:21 GMT

Greetings,

I have no idea what your background is or if this version is still under support? Did you try to call Canon and inquire about service or repair? Might be worth it. If this is a 1998 lens, ok, but the 2014 model might still be under support.

I'm not sure. I know others here who own this lens, maybe not the mk1, but they might have more to add. I hope you'll figure it out.

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

NirvanNa — Sun, 18 Oct 2020 10:28:47 GMT

Thanks for the reply

im searching for a diy repair at home, but just a repair part confirmation.

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

wq9nsc — Sun, 18 Oct 2020 13:05:54 GMT

Without at least a schematic, you really can't perform any sort of practical tests at home to determine which section is at fault. The AF/MF switch is about the only thing you may actually be able to test to ensure that the contacts are actually working on it, use a DMM or even an analog meter.

Otherwise, you could either flip a coin as to which module to order first but I would start with which one is cheaper and try it first. Or order them both and try to re-sell the one you don't use on an auction site. Most places that sell these sorts of parts won't accept returns because of customers either damaging parts or trying to return their own defective part.

Rodger

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

NirvanNa — Sun, 18 Oct 2020 13:43:31 GMT

Thanks wq9nsc

The AF/MF switch is about the only thing you may actually be able to test to ensure that the contacts are actually working on it, use a DMM or even an analog meter.

I can try take some picures to illustrate the inside connector.

On the first view, the AF/MF switch connector botton, look like new and the flat cables too, no damage signals.

I understand.

Probably the damage are in the USM motor. but like you said, its a 'flip a coin' situation.

can you tell me if the first image 1.JPG replacement part circula PCB part, is related by the Aperture function our is just the electronic information connector from the lens to camera?

best regards

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

ebiggs1 — Sun, 18 Oct 2020 14:10:18 GMT

"IT is a USM MOTOR our Pcb bionet problem?"

No, it is a Canon service problem. If you have to ask, you don't have the knowledge to repair it or how to realign it after repair. Call a Canon service center.

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

NirvanNa — Sun, 18 Oct 2020 18:28:12 GMT

thanks for the post,
but does not help in any things

Re: Canon 100-400 mm mk1 AF Doesn't Work (Help Diagnoses)

Waddizzle — Sun, 18 Oct 2020 18:52:31 GMT

@NirvanNa wrote:
thanks for the post,
but does not help in any things

As advised, you need to let someone qualified spend some hands on time with it. That is how electronic repairs work.