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01-27-2011, 02:32 AM - 1 Like   #1
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DA*16-50 Brought Back to Life

There have been so many posts about the problems with SDM in this model, and only a recent DIY fix, that I thought I'd add to the discussion, and let you know that the fix worked for mine.

Needless to say, I'm a bit pleased about it.

Nearly 12 months ago, the lens (attached to my K20D, where it had become the default optic) took a short tumble - about 150mm - into soft, sandy soil. Good sealing all round meant that a quick brush and blow or two later cleared off any grit-entry potential, but the SDM began to falter shortly thereafter, and eventually stopped altogether. Since then, it's had a few days of MF work on the K20D, but mostly stayed attached to the *istD (where the screw-drive functioned, at least) or in its pouch.

Discouraged by what I read in these forums, I left it there until the past few days, when I read of the Chinese Pentaxian who had dismantled the back of his 16-50 and manually worked the SDM rotor until it came back to life. I've attempted to find the post again, but it must be buried in one of the many threads about the SDM problem. It might not even have been on PentaxForums.

Regardless of all that, the technique has worked. What remains is to pin down precisely why the problem occurs (I've read some pretty unlikely theories about it, all asserted boldly, as they are) and whether we can be confident that there's now a standard, simple and inexpensive fix available.

It took me all of half an hour, including dismantling and reassembling, so that should be a reasonable benchmark for a professional bit of work, for which anyone worth their salt as a camera technician would probably charge a minimum of one hour's labour. The usual precautions about preparation, including cleanliness and proper lighting apply, of course.

I have to say that I am trained in Mechanical and Electronic Engineering, but I'm an Engineer, not a Technician. I'm more used to working on larger-scale devices (like motor-car insides, and then as a hobby), so I claim no special expertise. Until I saw the photos of the dismantled 16-50, I didn't really have the confidence to tackle this blind.

But it works! Maybe it'll need doing again in the future, but at least the spell is now broken, and a good independent Pentax technician should be able to pioneer a standard procedure and, if it needs it, a permanent fix.

Good luck with yours! (maybe a steady hand and your macro lighting setup might be better than luck)

Cheers
Rob

01-27-2011, 02:54 AM   #2
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Hope I don't need to do this.... Anyway, Congratulations!!!!!!!!!!!!

One Question, does this method bring dust inside the DA*? thanks!
01-27-2011, 03:13 AM   #3
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You might have meant this thread. It would be interesting if simply turning the screw drive would have "revived" the lens.

I'm not convinced that this cure works for all SDM failures but it seems to help with some cases.
01-27-2011, 03:13 AM   #4
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if it had some clear instructions .. then i would have called for this to be sticky

01-27-2011, 03:20 AM   #5
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QuoteOriginally posted by shang Quote
Hope I don't need to do this.... Anyway, Congratulations!!!!!!!!!!!!

One Question, does this method bring dust inside the DA*? thanks!
Thanks, Shang - it's daunting the first time, like many things in life, I guess.

There's always the potential for dust to enter when you take something apart in this fashion. Making sure you wear fresh clothing that doesn't shed lint is an idea - you can do the whole clean-room thing if you're really concerned about dust - but reasonable precautions should be sufficient to minimise the possibility, such as allowing dust to settle by turning fans off and waiting for a while before starting to dismantle the lens.

I should point out that when the lens is off the camera, and the rear lens cap isn't on, that there's a substantial slot around the base of the metal bayonet that can let dust into the insides of the lens. How far do you go in this regard?

But, hopefully you won't have to do any of this. What I really want is for Pentax service agents to pick up on the fact that there's a simple procedure that might be a better (and cheaper) first-line repair option for the average user (at least) and not just go for the routine of chucking the old motor out and installing another one, at a fairly hefty cost. I know that's the way of things now, but I don't think it's a good reason in this case, as the labour element is so small.

An ultimate fix will hopefully come, now a bit of the mystery's gone from the problem. I know that in some cases a motor replacement might be necessary, but I can't help wondering what percentage that needs to be.

And, if the Pentax service agents don't pick up on it, there'll no doubt be others who will, like Eric Hendrickson has done for the film-era gear.
01-27-2011, 03:22 AM   #6
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QuoteOriginally posted by Class A Quote
You might have meant this thread. It would be interesting if simply turning the screw drive would have "revived" the lens.

I'm not convinced that this cure works for all SDM failures but it seems to help with some cases.
Simply turning the screw drive didn't work for me - I had to turn the screw-head that's fixed directly to the rotor. And thanks, that's the thread I looked for when I started this thread, but couldn't find.
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