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07-20-2011, 06:49 PM   #16
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Ask Pentax first and if their repair quote is something you can swallow then go ahead and have it repaired, but if you think the quote is too high, then go right ahead and fix it yourself.
It won't hurt to ask for a repair quote first.

07-20-2011, 10:45 PM   #17
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QuoteOriginally posted by newarts Quote
If you glue the screws in it'll be hard to get them out when necessary.
I am not trying to be argumentative but when is it necessary to remove the lens mount from the body? I've seen a few threads in the forums about covering up certain lens contacts to coax extra functions from certain lenses but for the most, why would you need to be able to remove the lens mount?

Re: Increasing the screw size. Usually, when the screw shaft diameter is increased there is a corresponding increase in the screw head size, and most likely the countersink on the mounting ring would need to be enlarged for the screws to seat properly and not interfere with the lens' mount/dismount operation. When dealing with such tiny screws, for most people this is a can of worm better left untouched, imho.

Thanks,
07-21-2011, 02:44 AM   #18
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I have to agree with SveinG. Three months ago I dropped my K20D with FA50 onto concrete from 4 feet. In my case the upper body moulding was cracked and the AF intermittently hunted. It was only after playing around with it repeatedly, trying to assure myself that it was OK that I began to notice the AF issue occurring.

I bit the bullet, sent it and the lens away then got it back six weeks later. Total cost was $150 including courier to my door. They also sent me the damaged upper cover and in-built flash. Needless the say the AF issue has been resolved.

I recommend getting a quote first - you might be pleasantly surprised.
07-21-2011, 06:07 AM   #19
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QuoteOriginally posted by excanonfd Quote
I am not trying to be argumentative but when is it necessary to remove the lens mount from the body? I've seen a few threads in the forums about covering up certain lens contacts to coax extra functions from certain lenses but for the most, why would you need to be able to remove the lens mount?
I was thinking that if the camera ever needs repair it might be important to be able to remove the mount ring.

QuoteQuote:
Re: Increasing the screw size. Usually, when the screw shaft diameter is increased there is a corresponding increase in the screw head size, and most likely the countersink on the mounting ring would need to be enlarged for the screws to seat properly and not interfere with the lens' mount/dismount operation. When dealing with such tiny screws, for most people this is a can of worm better left untouched, imho.
Yes I'd mentioned that problem earlier - but it really is easy to increase the countersink diameter.

However I do think that the helicoid approach is a good one.

Also while writing this it struck me that another approach might be to use longer screws (depending of course on the material thickness).

Dave

07-21-2011, 05:12 PM   #20
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If you want to get the screws out of the epoxy after assembling it all, give them a rub over with something oily/greasy before you screw them in/put them in place. Wipe off any excess, only need enough to wet the screw surface.
Usually this will let a thread form in the set epoxy and be able to withdraw the screw as the epoxy cannot bond to the slippery surface.
Having said that, all things get harder to do as they get smaller.
Nothing to loose, everything to gain I guess.
07-21-2011, 06:44 PM   #21
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Well, I'm currently running some tests with several different adhesives to see how well I can work with them to thread screws back in. There are other issues I need to test, but I'll get to them next. The main one is figuring out exactly what kind of plastic the mirror box is, like JohnBee mentioned, so I can match the adhesive to that. From what I've read, it's polycarbonate. I'm not sure what works best with polycarbonate...

Jamesm007: I really like the idea of using the Helicoils. It seems they could be the most secure way to go. But I looked for the stuff online, and the problem is that I can't find any that are small enough. The screw size M2, but the smallest Helicoil seems to be M2.5, which means I'd have to get new screws. But I also am having trouble finding screws that would work. A thorough search of McMaster-Carr's website yielded no screws that had a low enough profile head (the one in the K-7 has about a .5 mm tall head). Do you know any better Helicoil options than what I found?

I just realized a little while ago that the plastic standoff on the bottom (which was the worst off of all 5) is actually completely broken. As in it split in half so that there's no hole any more. If I can find the right adhesive, maybe I can fix it. Otherwise, I'm not sure. Again, the biggest problem with that is that it's the mirror box that's broken (I know this is the only problem since I can fix the aperture issue by just bending down on the lens to push it all back together), which is the most central part of the camera. The entire thing would have to be taken apart and reassembled onto a new mirror box. I might ask CRIS what it would cost, but I'm sure it's astronomical.

I'm going to try to find a really good polycarbonate adhesive and fix it. If that doesn't work, I might try to order a new mirror box (if that's possible) and reassemble the whole thing myself. A monumental task, I know, but as auspentax pointed out I don't really have anything to loose. I'll keep everyone posted. Thanks again for all the ideas.
07-21-2011, 09:22 PM   #22
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Try a good hobby shop for glue. Not Hobby Lobby. Look for a hobby shop that caters to the model train or model airplane people. Tell them you want to glue polycarbonate.
07-22-2011, 06:18 AM   #23
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Devcon Plastic Weder works well on polycarbonate and has good consistency for your tasks.

ITW Devcon | Plastic Welder?

07-23-2011, 07:43 AM   #24
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QuoteOriginally posted by rhodeswv Quote
Well, I'm currently running some tests with several different adhesives to see how well I can work with them to thread screws back in. There are other issues I need to test, but I'll get to them next. The main one is figuring out exactly what kind of plastic the mirror box is, like JohnBee mentioned, so I can match the adhesive to that. From what I've read, it's polycarbonate. I'm not sure what works best with polycarbonate...

Jamesm007: I really like the idea of using the Helicoils. It seems they could be the most secure way to go. But I looked for the stuff online, and the problem is that I can't find any that are small enough. The screw size M2, but the smallest Helicoil seems to be M2.5, which means I'd have to get new screws. But I also am having trouble finding screws that would work. A thorough search of McMaster-Carr's website yielded no screws that had a low enough profile head (the one in the K-7 has about a .5 mm tall head). Do you know any better Helicoil options than what I found?

I just realized a little while ago that the plastic standoff on the bottom (which was the worst off of all 5) is actually completely broken. As in it split in half so that there's no hole any more. If I can find the right adhesive, maybe I can fix it. Otherwise, I'm not sure. Again, the biggest problem with that is that it's the mirror box that's broken (I know this is the only problem since I can fix the aperture issue by just bending down on the lens to push it all back together), which is the most central part of the camera. The entire thing would have to be taken apart and reassembled onto a new mirror box. I might ask CRIS what it would cost, but I'm sure it's astronomical.

I'm going to try to find a really good polycarbonate adhesive and fix it. If that doesn't work, I might try to order a new mirror box (if that's possible) and reassemble the whole thing myself. A monumental task, I know, but as auspentax pointed out I don't really have anything to loose. I'll keep everyone posted. Thanks again for all the ideas.
There are lots of M2 self tapping inserts. The 4.5 is the thread pitch. The body uses 4.5 for screws going into plastic and 4.0 for screws going into metal. To me this is why a coil or insert would be stronger as it would have finer threads to hold the lens plate and courser threads to hold the insert.

http://www.yardleyproducts.com/Trisert_Regular.pdf

Trisert regular & short self-tapping inserts for plastics, soft metals, wood - Yardley

Self Threading Insert - Flange on O.E.M Fastening Systems

Do searches with "Self-Threading Inserts" and look at Dodge type inserts (the second link in my OP) you will come across many!

The problem with fillers is the tremendous(!) stress the screws are under from thermal expansion and contraction and constant movement, hard movements! The material may lose bond over time. You have two different materials bonding to each other that can loosen over time. You can find self taping course inserts (4.5 or more) with machine type fine thread for the screws to hold down the plate (4.0). Just dig around! Switching to machine threads for the plate will increase strength and using course self taping screws will closely restore the original design spec. Providing you have enough material around the rest (I see the one cracked).

Also I would think CRIS cameras or others know how to do this repair. If they did make this a break point they know how to fix it and my bet is they use self tapping inserts on any stripped threads.
07-25-2011, 08:40 AM   #25
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I'm still working on it, but I'm a little unsure now what's actually causing the aperture problem. I initially thought it was due to the misalignment of the lens/mount, but I'm wondering now if there was some damage caused to the row of contacts.

My row of contacts in the camera body moves around. It sort of floats around as if allowing for some slight misalignment with the mount. Is this normal? Should the row of contacts "float" around (twist, turn, and go up and down) like this? If someone could confirm that or tell me that's not supposed to happen, that would help me out a lot. Thanks!
07-25-2011, 08:58 AM   #26
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It's not supposed to happen. Not the entire row anyway. Each contact has a spring behind it to accommodate putting the lens on so you May be able to push the contact downward but that should be it. Something else is broken.

07-25-2011, 09:02 AM   #27
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Yeah, ok. The entire plastic row on mine moves around all over the place, as if it isn't hard mounted to anything at all, just a few wires or something. That's completely aside from each contact moving up and down with springs.

Thanks, JeffJS. I think I may have an electrical problem to work on...
07-25-2011, 03:32 PM   #28
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QuoteOriginally posted by rhodeswv Quote
Yeah, ok. The entire plastic row on mine moves around all over the place, as if it isn't hard mounted to anything at all, just a few wires or something. That's completely aside from each contact moving up and down with springs.

Thanks, JeffJS. I think I may have an electrical problem to work on...
You know you can download the service manuals up to the K20D. Pentax did not make many structural changes with each new model. They are closely related all of them in concept, of course they are very different but its like looking at all 90's GM cars with 3800 engines. Different yet similar. Not sure if the K-7 is totally different.

With the K20D the lens electric contact has a set pin and screw to hold the contacts in place. Also note everyplace that says "G134" is areas that need something? I am not sure if its light oil, grease or...

Downloads


Last edited by jamesm007; 07-25-2011 at 03:40 PM.
07-25-2011, 04:03 PM   #29
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QuoteOriginally posted by jamesm007 Quote
You know you can download the service manuals up to the K20D. Pentax did not make many structural changes with each new model. They are closely related all of them in concept, of course they are very different but its like looking at all 90's GM cars with 3800 engines. Different yet similar. Not sure if the K-7 is totally different.
Thanks James, that's great to know. It seems like op should find the set screw site for the contact assembly and glue it too.

There is a reasonable chance that the mounting ring will hold the contact assembly in place with no glue because they are geometrically keyed.
07-25-2011, 04:35 PM   #30
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Should the row of contacts "float" around (twist, turn, and go up and down) like this?

Taking the OP pic into photoshop shows no damage that I can see(!) to the lens contacts. You say its keyed so that got me to thinking how can it move around? I think the lens plate was put on too high??? The contacts are As you held by a small pin and then a screw on one side, the other side is keyed into the lens plate to keep it still...

Maybe bad news. The K-7 is a weather sealed camera. Thats a big hole. All manual show putting on the lens ring then putting the front cover on. The oring for the lens mount seal is in the middle of the metal ring, but it appears to be ridged (steps bigger on bottom) so when you put the front cover over it, it forms a tight seal. This would account for any problems you may have trying to put it on with the cover still there. The ring may have ripped right out of the cover doing damage to the cover as well. Those parts are pretty cheap. Order a new cover or take the cover off then put on the lens mount ring and cover to form an air tight seal.

I think the step up behind the oring is there. Take a look at your ring. Maybe the K-7 seals from the outside? But here is how the K20D is sealed. The mounting plate goes on the mirror box and has an oring then a flange. The cover presses tight against this to form an air tight seal.




Last edited by jamesm007; 07-26-2011 at 04:13 AM.
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