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12-08-2010, 04:23 AM   #1
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Need help with my FA85 - AF problem

Hello all,

Ash in this other post (https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/124945-da-35mm...ml#post1292663) said that, and I quote: "Glad to hear this wasn't our first screwdrive AF casualty - at least that I've heard of..."

I hope that my FA 85 isn't the first one.

The AF only seems works from far to near. When going from near to far it stops half way and seems to be stucked. I've tried with a K10D and a Z1-p with the same results.

When in MF the focus goes smoothly in both directions.

Does any of you had a similar case? Is there a way to solve it or do I have to send to repair (with is a huge PITA)?

Thanks,
Luis

12-08-2010, 05:34 AM   #2
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No idea.
What I would test is this:
Remove the lens from the camera.
Put it in AF Mode and use a small screwdriver to turn the AF shaft.
Do you feel anything strange? Is it working in both directions?
12-08-2010, 05:47 AM   #3
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Does this happen with other lenses?

I know my DA21 had problem with focus at close range, it also got stuck and I had to manually get it out of that range. I felt the friction when moving it manually, however. Long story short, some tumblers were misaligned. A pro opened it, reset everything, and it's now smooth as butter.

Maybe someone like Eric or a local repaiman could fix it for you at a relatively low price.
12-08-2010, 09:30 AM   #4
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QuoteOriginally posted by bdery Quote
Does this happen with other lenses?
No, the others are working fine.

QuoteOriginally posted by bdery Quote
Maybe someone like Eric or a local repaiman could fix it for you at a relatively low price.
That's exacly what I was trying to avoid. I know the lens is worth it but I was hoping that it was I who was doing something stupid.

I also tryed blende8 sugestion and now it is a bit better. It works in both directions but slower from near to far. I guess it will go to repair.

Thank you both.

Luis

12-08-2010, 10:21 AM   #5
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I was going to respond (and still will) but reading through the thread you've made your decision. I had an FA100 f2.8 Macro that basically did the same thing. I had purchased it from a Japan seller on ebay and when I got it, it would only AF in the middle of the range. Almost as if the limiter had been set but it wasn't. In the case of this lens though, I couldn't even Manual focus it properly. The screw mechanism inside the lens had gone south and I returned the lens. Good luck with the repair. That's one lens I would say you won't replace for less $$$$.

12-08-2010, 11:43 AM   #6
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Sand or some other dirt in the gears could do this. The camera will believe that it came to the end of the focus throw if there is enough resistance and turn. How does it feel when you focus manually? Any resistance or strange sounds?
12-08-2010, 12:02 PM   #7
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QuoteOriginally posted by Douglas_of_Sweden Quote
Sand or some other dirt in the gears could do this. The camera will believe that it came to the end of the focus throw if there is enough resistance and turn. How does it feel when you focus manually? Any resistance or strange sounds?
My wild guess is that the lens has something like the slotted wheel-optical counter arrangement here, to give the camera some distance and focus travel data:



Dirt in this system would send the wrong data, confusing the camera.

It's all academic, because I wouldn't take apart an FA85 even if I had one, let alone suggest someone else do it. It's easier than the pictured lens, but the price of failure is too high.
12-08-2010, 04:45 PM   #8
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QuoteOriginally posted by Douglas_of_Sweden Quote
Sand or some other dirt in the gears could do this. The camera will believe that it came to the end of the focus throw if there is enough resistance and turn. How does it feel when you focus manually? Any resistance or strange sounds?
After reading your info I tryed to move gently the focus ring and now I think it may be some resistance but I'm not sure as it may be my imagination.

As for sounds, the only abnormal sound is when trying to move from near to far and stops before aquiring focus.

Your hypothesis makes sense. Thanks for your input.

Luis

12-08-2010, 04:53 PM   #9
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QuoteOriginally posted by Just1MoreDave Quote
It's all academic, because I wouldn't take apart an FA85 even if I had one, let alone suggest someone else do it. It's easier than the pictured lens, but the price of failure is too high.
I wouldn't try that either on a such rare and expensive lens. Besides I open once a Pentax A28/2.8 (when they were inexpensive on eBay) and ended up screwing it.

By the way, a few hours after trying blende8 sugestion that made the lens (sort of) work, it retuned to its previous condition stoping half way.

Does any one know a good place to repair the lens in Portugal? And in Europe?

Eric (for now) is not an option as sending the lens outside Europe is a huge hassle with customs.

Thanks,
Luis
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