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09-02-2013, 08:13 AM   #1
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What is this piece called? From Pentax lens internals

Sorry if this is the wrong place, didn't see anywhere better though.

So I was working on my DA 35mm f/2.4 because a couple of months ago, it got blown out of my bag (helicopters are neat) and thrown through the dirt. Since then, I'd noticed some grinding in the focusing mechanism, and since it was bought secondhand, I decided I would clean it out myself.

Since it didn't have a lens disassembly post already, I planned on doing that too so I went a little further than I needed to. All was well until I started putting it back together and learned just how tight some tolerances are.


This is the piece that got mangled during reassembly for being a fraction of a millimeter off-center. Fun, right? I was wondering if anyone knew what this little thing was called, so I could hunt down a replacement somehow. Buying a new lens isn't an option, as I'm a poor college student.

All help would be greatly appreciated, thanks!

09-02-2013, 08:35 AM   #2
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I believe that should be the part where it provides feedback as to the distance that the focusing group moved..

e.g. in zoom lenses, this thing provides feedback as to the zoom range that it travel.. I might be wrong but is the lens AF-ing correctly?
09-02-2013, 08:44 AM   #3
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QuoteOriginally posted by SyncGuy Quote
I believe that should be the part where it provides feedback as to the distance that the focusing group moved..

e.g. in zoom lenses, this thing provides feedback as to the zoom range that it travel.. I might be wrong but is the lens AF-ing correctly?
That's what it looked like to me too, but I was confused because... this is a prime. I'm putting it back together now but I have a class in 15 minutes, so I'll respond with whether or not AF works after that.
09-02-2013, 09:01 AM   #4
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This kind of piece is called "brush" as motors use for example. I searched for "contact brush pentax repair" and this turned out:
Pentax 70-210 Repair
The guy replaced it with a homemade brush from some clips. You could also try to straighten your brush as it is not broken. If it isnīt strong enough, maybe you can reinforce it with some soldering tin. (probably need to sand it so that the tin sticks)

The brush closes the loop to provide feedback regarind focusing distance. This is a parameter used by the focusing engine to determinate how the AF mechanism will procede and also writen on the EXIF.

PD: I am a poor college student too so thumbs up for DIY fast and cheap and go out play.

09-02-2013, 10:50 AM   #5
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Ah, that's the piece exactly! Once I get a hold of a pair of tweezers later on, I'll give it a shot at straightening it. Otherwise I could try hunting down some wire like his, but I don't think I have anything this small. Pictures are incredibly deceiving, these pins are <= 1mm in width.

Worst case scenario, I could just try to find an as-is F lens and salvage it from that, since it seems to be a common part in all of the autofocus lenses.
09-02-2013, 11:12 AM   #6
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This is used to detect the focussing distance of the lens, zoom lenses have an additional one for the focal range.
Usually these can be removed before disassembly, and mounted after assembly, look for a hidden access to this part on the lens barrel.
I never have used/handled this lens, so can't give exact instructions..
The access can be under the focussing rubber grip, or some glued type plate etc. They are very creative in finding ways of hiding this access.
Start with straigtening this brush, but they are fragile, so bent them carefully.
09-02-2013, 11:54 AM   #7
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QuoteOriginally posted by glasbak Quote
This is used to detect the focussing distance of the lens, zoom lenses have an additional one for the focal range.
Usually these can be removed before disassembly, and mounted after assembly, look for a hidden access to this part on the lens barrel.
I never have used/handled this lens, so can't give exact instructions..
The access can be under the focussing rubber grip, or some glued type plate etc. They are very creative in finding ways of hiding this access.
Start with straigtening this brush, but they are fragile, so bent them carefully.
Well since I've not put it back together yet, I looked for any access doors but can't find any. I think the DA 35mm is just too small for one to be feasible. The time this brush is made available for removal is right when it's very easy to damage it, heh.

Glad to hear zooms have two! I just went ahead and ordered an as-is 35-80mm FA zoom to scavenge from ($6 before shipping) just in case straightening it doesn't work. I love this lens, no way I'm going to let a little error on my part take it out of commission.
09-02-2013, 09:41 PM   #8
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QuoteOriginally posted by Harrison Quote
Well since I've not put it back together yet, I looked for any access doors but can't find any. I think the DA 35mm is just too small for one to be feasible. The time this brush is made available for removal is right when it's very easy to damage it, heh.

Glad to hear zooms have two! I just went ahead and ordered an as-is 35-80mm FA zoom to scavenge from ($6 before shipping) just in case straightening it doesn't work. I love this lens, no way I'm going to let a little error on my part take it out of commission.
Erm... I'm not too sure if they would be of the same size.. I'll keep my fingers crossed for you. If it fails, i'll pm you my address instead..

09-03-2013, 07:01 AM   #9
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QuoteOriginally posted by SyncGuy Quote
Erm... I'm not too sure if they would be of the same size.. I'll keep my fingers crossed for you. If it fails, i'll pm you my address instead..
Well I'll find out! From my research it seems there are only two versions,a5 pin one anda four pin one. Even if the lens i picked up only has the four pin one, I may be able to make it work as it seems only the three middle ones are used.

Do you have the piece to fix it or something?
09-03-2013, 10:56 AM   #10
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Just a fair bit of warning - I broke one of the little legs (not the whole pair, just 1 of the pair) and my DA 21 Ltd won't focus anymore. It's the little leg at one end. So you may need all 5, depending on your lens.

That being said, having seen this thread, I'm going to buy a cheap F lens to see if I can get mine fixed.
09-05-2013, 12:04 PM   #11
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Welp, bad news The lens I purchased, a FA 35-80mm, only has the 4 pin versions of the contacts, not the 5 pin one. Dunno what I'm going to do now, I guess try to figure out a way to hold a 4 pin one in and hope it works.
09-05-2013, 12:17 PM   #12
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QuoteOriginally posted by Harrison Quote
What is this piece called? From Pentax lens internals
You can tell I'm technical, it's a called a broken bit.

Good luck with getting it fixed up and put back where it should go, wherever that is.
09-05-2013, 12:20 PM   #13
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QuoteOriginally posted by Harrison Quote
Welp, bad news The lens I purchased, a FA 35-80mm, only has the 4 pin versions of the contacts, not the 5 pin one. Dunno what I'm going to do now, I guess try to figure out a way to hold a 4 pin one in and hope it works.
Damn, I bought the same lens. Ugh
09-05-2013, 12:28 PM   #14
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QuoteOriginally posted by Harrison Quote
Welp, bad news The lens I purchased, a FA 35-80mm, only has the 4 pin versions of the contacts, not the 5 pin one. Dunno what I'm going to do now, I guess try to figure out a way to hold a 4 pin one in and hope it works.
It is a zoom, so it should have two of these, add it to the other one.
09-05-2013, 12:42 PM   #15
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QuoteOriginally posted by glasbak Quote
It is a zoom, so it should have two of these, add it to the other one.
Oh, that's a good idea! I'll definitely try that. One's held in with plastic welds, so I'm going to have to be super careful getting it off to use, but stacking may work. I'll report back in a bit.
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