Yoshizen's Blog

Cause of Broken Zoom

Sigma AF Motor5-001

———————— (Photo above, Right — Note a clack in the white nylon gear )

Yet again, this is about the same broken Sigma Zoom Lens.

While examining the mechanism, electronics, I’ve been puzzling why

this lens was not working.   It seems everything are functioning. —– ? ? ?

—– Then I noticed, when the AF motor was connected to the battery

and rotating, focus mechanism only moves a little.  In both direction,

gears rotates only short time even though the motor was kept running.  

—– On the end, I discovered,  a gear connected to the motor has a clack, 

so, it’s loose from the shaft and slipping.


In theory, it is easy to replace the gear like this, which is not expensive.  

BUT in practice, in order to access this part of the mechanism, the whole

lens has to be disassembled. —– Considering the time and the expertise,

just  change a small gear which cost (to the Sigma) may not be more than 50P,

still the service charge would be more than £100.  

= good second-hand would be even cheaper. 


In my life, I rarely paid a service charge to the camera company.

 1) I don’t brake a camera.   2) If it started malfunctioning, I repair myself.  

3) If it was beyond repair, I disassemble and use it for experiment. (and have a fun !)  

4) Being as a technical writer, the service engineers are my good friend and to keep

cosy relation, camera company wouldn’t charge us.  (often, broken camera is a bad

news which the company want to keep it  in secret.  

And our feed-back is indispensable for them. )


In principal, the Gear shouldn’t break, still, as I saw the broken gear like this

only  the second time, it is rare occurrence.  = it should be OK

= and if it happened on you,  you are extremely unlucky.  

Have a pint or two and blame the God.  🙂



Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: