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01-27-2013, 02:10 PM   #1
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Electrical contacts question.......

I have a SMC F 50mm f1.7 lens that won't auto-focus consistently. I mean, sometimes it will focus and sometimes it will not move. The aperture information and focus confirmation information still shows up in the viewfinder and the LCD screen, but it just won't focus sometimes. I have cleaned the contacts and it would work for a while, but now cleaning doesn't help anymore. It appears that some of the small contact points don't protrude out as far as some of the others. Has anyone had experience with this? Is it repairable? Do you know what it costs to repair it if it is able to be repaired?

I have a K100D, KX, and K5 and it has the same problem on all bodies and this is the only lens I own that has this issue. Thanks in advance for any help.

Ray

01-27-2013, 03:05 PM   #2
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Each of those contacts has a little spring behind it, and the spring touches a flexible PC board on the other side if I remember right. You might be able to take off the mount, stretch the springs a bit and reassemble. In reality, this job is more like take off the mount, have all five contacts leap one way and five springs go the other way before you blink, and the next hour tracking these parts down. It goes better the second time. A JIS screwdriver is helpful for the mount screws.
01-27-2013, 03:15 PM   #3
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Do you have a preferred brand of JIS screwdrivers. I just learned of them a minute ago.
01-27-2013, 03:52 PM   #4
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QuoteOriginally posted by Just1MoreDave Quote
In reality, this job is more like take off the mount, have all five contacts leap one way and five springs go the other way before you blink, and the next hour tracking these parts down.
If you want to do this, get a large clear plastic bag and do the work inside it. That way MOST of the parts will be in the bag and you won't have to spend as much time tracking them down. Umm by inside I mean with the lens and your hands in the bag, not all of you. It's hard to breathe in there. Just covering all bases.......

01-27-2013, 04:13 PM   #5
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Moody makes some fine tools.
Browse the Moody Tools Catalog
http://www.moodytools.com/MTI_CATALOG_PAGE_11.pdf

Last edited by Ex Finn.; 01-27-2013 at 05:13 PM. Reason: Removing quote that was directed at Just1MoreDave
01-27-2013, 04:58 PM   #6
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QuoteOriginally posted by aoeu Quote
Do you have a preferred brand of JIS screwdrivers. I just learned of them a minute ago.
I am not sure whether I am extremely hard on screwdrivers or there are no good ones. I somewhat liked the Hozan D-130-75 (grip too small, though) until I messed up the tip yesterday. Hozan confusingly calls this a 00 size, the Phillips size that will sort of fit but not well enough for a tight screw. Googling the Hozan shows they changed the handle.
01-27-2013, 05:58 PM   #7
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I had a local company take a look at it and they want $90.00 to repair it. Does anyone have the contact information for the retired Pentax technician who lives in TN?
01-27-2013, 06:38 PM   #8
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QuoteOriginally posted by sawtooth235 Quote
I had a local company take a look at it and they want $90.00 to repair it. Does anyone have the contact information for the retired Pentax technician who lives in TN?
Eric Hendricson:

pentaxs.com



Steve

01-27-2013, 07:09 PM   #9
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QuoteOriginally posted by stevebrot Quote
Eric Hendricson:
+1
I believe he is around Knoxville area. I have never heard a bad thing said about him just high praises on his work and his prices
01-28-2013, 07:20 AM   #10
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Thanks Steve and Patrick.

Ray
01-28-2013, 09:00 AM   #11
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QuoteOriginally posted by sawtooth:
It appears that some of the small contact points don't protrude out as far as some of the others.
QuoteOriginally posted by Just1MoreDave:
Each of those contacts has a little spring behind it . . .
If you can plainly see that certain contacts "don't protrude" as much as others it may be that dirt, debris or other greasy crud has accumulated around the insulated 'collars' around the contacts. (Place a straight edge across the base plate to help see this). This sometimes happens with aggressive attempts to 'clean' the contacts with cloth or pencil erasers. Debris can either prevent electrical contact within the base plate or inhibit full movement of the spring-loaded contact.

Without saturating/flooding the mount, apply a drop of naptha/lighter fluid to each contact and exercise the contacts.

H2
01-28-2013, 10:53 AM   #12
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Just a simple note, except for the third contact from the lens locking pin, as long as the contacts come out as far as the lens base there should be no issue as these pins are all shorted when a K mount lens is attached, that is how the camera knows there is a non A lens present. The third contact is differ on the camera side, it does not contact the lens base and needs a pin that positively protrudes. That pin is the one that tells the camera a lens is in the A position
01-29-2013, 01:51 AM   #13
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The contacts you are referring to on the lens mount are not used by the autofocus on F series lenses since the motor is in the camera. The only contacts used by the autofocus are on SDM lenses.

The contacts you are referring to transmit aperture information to the camera. I think that you may have some mechanical problem with the lens.
01-29-2013, 04:46 AM   #14
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QuoteOriginally posted by pentaxman Quote
The contacts you are referring to on the lens mount are not used by the autofocus on F series lenses since the motor is in the camera. The only contacts used by the autofocus are on SDM lenses.

The contacts you are referring to transmit aperture information to the camera. I think that you may have some mechanical problem with the lens.
This is not quite accurate, the first 6 contacts from the lens mounting pin transmit maximum and minimum aperture to the camera, as well as the aperture ring in the A position, the 7th transmits focus data to the camera, including focal length of the lens.
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