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Sigma 70300 acting strange




I have Sigma 70-300 APO Macro lens that I use on my Maxxum 7. Been using it for around 8 month with great results. But suddenly couple of days ago it developed rather strange and disturbing behaviour.

When I switch the camera on then as normally the camera-lens wake up and lens starts to do some pre-focus or whatever Minolta cameras tell the lenses to do when switched on. But instead of doing small "whizz" it looks like lens tries to screw manual focus ring in unknown direction. Lens motors are wrooming away for 2-3 seconds with no result and then they stop, the camera turns itself on and everything seems to be OK. Lens zooms ok, focuses ok etc.

It all starts over when I switch the camera off most of the times. Lens tries to focus back into it's "sleeping" position, rattles the focus ring for 2-3 seconds, then stops and camera finally manages to shut down.

Tried same lens with my Dynax 505si super as well, same behaviour. Checked both cameras with Minolta 28-80 zoom and both worked OK so I guess it's the Sigma lens that is having problems.

The only reason I can think of is that I left the camera in my car (inside the camerabag) for the evening and it might have caught some moisture as a result because it was a bit misty evening. But there isn't that much moisture inside the car... Then again I've left the camera out before and at the same time my Dynax was there as well. So I'm really having trouble coming up with a reason.

Anyway, has anyone had similar problems with Sigma lenses before? Any suggestions as to what to do? Because it's the lens that has the problem there's probably no point trying to "reset" the camera with the lens attached and hope that lens electronics sort themselves out...

I still have valid guarantee on the lens but would really hate to use it as it means posting the lens back to Germany where I ordered it from...

Thanks in advance,

Siim Teller - Estonia
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Well-Known Member
All you can do is clean the contacts between the camera and lens ...

... and perhaps try to dry out the lens by keeping it a little warmer and drier than usual.

Heating a lens is tricky, since you probably don't want to put it in an oven, but if you preheat an oven to 125° then turn it off, and then put the lens in for a few hours wrapped in a towel, that may evaporate any moisture or humidity that may be inside - but the lens electronics, if properly designed, should be immune to "normal" humidity variations.

Otherwise, have Sigma look at it before the warranty is over.

Good testing to try it on other cameras - which we all can do at a local camera store I guess.


Love and hugs,

Peter Blaise Monahon

Minolta Photographer

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Update. Did not try that oven test but the lens has been indoors ever since, problem still there. What's worse - a friend of mine who bought the same lens at the same time reported that her lens has developed similar problems. We're both sending them back for repairs.

Has anyone else had problems with Sigma 70-300 F4-5.6 APO Macro lens?


Siim Teller
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New Member
Hi There....

It looks like you have a broken rack and pinion gear tooth . Well i had the problem last year. I came back froom the US and had the problem. I turned the Dynax7 on and the lens went grrrrrrrrr trk trk trk trk....and it goes into time out.

Well...i dismantled the lens and find out that its due to a worn out gear at the INFINITY.

One possible cause is the faster higher torque AF of the Dynax 7 that may have caused the wearing of the tooth of the rack gears.

Send the Lens for repair as its still under waranty and they change exactly that part (the whole focusing ring.

One possible scenario is you may have left the camera on and kept the camera in the bag . AF may have kicked in IN THE BAG???? Maybe...

The rack and pinion gears are PLASTIC so its easily worn.....




That's Sigma. It has plastic focusing gears, and one of them (probably on the focusing ring) is broken at the infinity position. If you have waranty, send the zoom to repairing.
And buy Minolta zooms next time, I didn't hear for anyone with brokem gears...

Best regards, Joe