Problem with K10D and Bigma combination?

Hi everyone, I traded up my Pentax isDS and Sigma 170-500 to a K10D and Sigma 50-500 (Bigma) Combination a few months ago.

Looks like I have a problem, as the Autofocus has now gone for a second time on the Bigma and it is back with Sigma for repair.

Something nasty is happening inside the lens resulting in a small geared cog coming loose and dropping out of the lens mount on detaching from the body ( both times) . I have spoken to the Sigma technician today who suspects that the K10D motor might be quite 'torquey' resulting in the probelm. The retailer / sigma have offered to repair , replace or refund, but ideally I'd like to know what is going on before I decide.

Has anyone got a similar combo, and if so any problems?

So what they're saying is that the K10D is too powerful? Is that a bad thing?

Well, I don't know ifI'd go for that story. But I have a few lenses, some going on 10 years old.
I got my first Sigma lens (18-200mm) last year. It lasted less than 60 days before the focusing components fell apart. Still, they wanted $80 to repair. (Yes cheaper than a new lens, but should a repair fee really be charged in that time??)

I hear a lot of good things about Sigma, but I hear almost equal amounts on lenses needing to be returned for one thing or another.

It seems to me that if this problem is not happening with pentax lenses then the fault lies with Sigma. It seems ever so slightly cheeky for a lens manufacturer to be suggesting (reading between the lines as it were) that Pentax cameras don't take their needs into account.

I think this is another one of those cases of "well they would say that, wouldn't they."

I would expect a lens as expensive as the Bigma to be built well enough to handle a pro grade focusing motor TBH. True the K10 has a more powerful motor than previous Pentax DSLRs (at least the later *ists anyway, I've never used an original *istD) but that shouldn't be the end users problem.

I bought the Bigma with my K10D (told the wife it would save me money not having the kit lens ) and so far so good (finds wood to touch).

Dont know if the K10D motor is more powerfull or not, if it is then why would Pentax do this when the camera is designed to accept the new HSM lenses?

I just chatted with a couple of blokes I know with K10Ds and Bigmas - neither reported any problems with the combination. Both swapped over from Ist D to K10D and both already had the Bigma. I suggest you swap it for new one and see how that goes.

Whatever you decide, be sure to pass the info/results along here as well, please - I've been considering a Bigma....

Thanks for your comments

I should be hearing from Sigma early next week, and will report back the findings!

The results I had with the Bigma (before the failures) were excellent, Luckily I still have my Sigma 170-500, as a reserve, which is working fine on the K10D!,

Me too. Look forward to the update

I have received my lens back from Sigma, a week turnaround as an urgent repair. The technician has replaced and adjusted the gears, which he assures is the best solution to the problems that I have been experiencing but if the fault should re-occur Sigma will replace the unit.

Well the Airshow season is approaching so I will be out and about using the Bigma in anger with my K10D. Plenty of time left on the warranty, so I am happy unless it fails again!

The only gripe is the £20 Royal Mail Special Delivery charge ( Bigma is over 2 Kg!) to send the lens back for repair!