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02-02-2009, 03:41 AM   #1
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Fix a Spotmatic Top Case disjunction

Hi.

So I picked up this Spotmatic in a great condition (along with a 50/1,4, also in a great condition, albeit yellow ;-), and even though it was sold as an "as-is" item, it's mostly functional. I need to replace light seal foam and mirror shock foam, and I already have a kit for that.


One crucial problem is that there's a slight disjunction between the top case and the body which creates a step, if you will, just above the metering switch. Check out this photo on Flickr:


Asahi Pentax Spotmatic + Super-Takumar 50/1,4 on Flickr - Photo Sharing!



The step gets in the way of the switch and basically makes it impossible to flip the switch up, unless I use both hand, and push the top case while flipping the switch. Not very practical out in the field ;-)

Anyway, I was wondering how hard it would be to fix this? Does anybody have an idea?

I'll be honest and say I'm not willing to spend money on it; I got it for the glass, and I thought the body would be a nice bonus to play around with, but I'm pretty much entrenched in digital right now. Besides, I like being all ghetto and DIY. I'm pretty good with mechanics and dissection. Any help will be greatly appreciated. Thanks!

02-02-2009, 07:03 AM   #2
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The yellow 50/1.4 can be cured quite easily by leaving the lens in a widnowsill for a few days.
The UV radiation does the work for you

Now that pesky part I do not know, there is a full maintenance manual for the Sportmatic at pentax-manuals.com (national camera service manual I think) where exploded diagrams are found.
I do not really know if the porblem is just a bent piece of metal or something larger.
02-02-2009, 08:04 AM   #3
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Looks like it has either been bumped (dropped) or disassembled and reassembled improperly. There are service manuals here. I think if you remove the top plate and reassemble carefully you'll be ok.

Go slow - be gentle - good luck.
02-02-2009, 09:47 AM   #4
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I'm guessing you're saying the switch hangs up on the metal seam, there? I don't know if those edges are supposed to butt up against each other and thus lie flatter, but possibly, if that's so, it's just taken a bumpand could be popped back into place. Worse come to worst, you could probably just take a little material off the underside of the switch with a hobby file.

02-02-2009, 07:33 PM   #5
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QuoteOriginally posted by titrisol Quote
The yellow 50/1.4 can be cured quite easily by leaving the lens in a widnowsill for a few days.
The UV radiation does the work for you

Funny you mention that, I just uploaded some pics today to show what I did. A bit more radical than the windowsill method ;-)

Super-Takumar, before-and-after on Flickr - Photo Sharing!
IMG_0530 on Flickr - Photo Sharing!





Thanks for the comments, I guess I'll see if I can do a disassembly. There's definitely a total disjunction because while this side the top case is jutting out, the other side, the top case is depressed; it's like the entire top case is shifted to the right about 1mm.

If a disassembly seems too risky, I'll go for the "carve" method ;-)
02-03-2009, 12:08 AM   #6
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Well, there is a difference in the UV radiation between the sterilizer and the sun.
For some reason the UV lamps are not in the right wavelength and the windowsill method is faster and more eficient.
02-03-2009, 12:22 AM   #7
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QuoteOriginally posted by titrisol Quote
Well, there is a difference in the UV radiation between the sterilizer and the sun.
For some reason the UV lamps are not in the right wavelength and the windowsill method is faster and more eficient.

DUH! Really!? And here I thought that the UV lamps would be much more powerful and would therefore cure it faster!


OK, it's going to the windowsill next. After today's snowstorm passes ;-)
02-03-2009, 01:00 AM   #8
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Google is our friend
Disassembly and Cleaning of the F1.4 50mm Super Takumar Lens

QuoteOriginally posted by mypentax.com:
Problems peculiar to this lens type.

Many examples show yellowing of the inner elements. This is due to the use of radioactive Thorium in the glass formulation. I believe that the cause of the discolouration may be attributable directly to the effects of the radiation itself as the Thorium decays. However, there is no need to worry, the level of radiation is very low, and is mostly stopped by the glass anyway. I am told that some lenses used for aerial surveillance in WW2, are hot enough to fog film after a few days!

This can (Reportedly) be rectified by exposure to UV for a period of two or three weeks. This method works quite well if the source of UV is Californian sunshine, but living in Britain I have not been available to verify the sunlight cure. It is claimed that artificial UV lighting will clear the glass in a little more time. My own experiments suggest that only 'hard' UV will suffice. (The sort that is produced by tanning lamps, or (more extreme) arc-welding equipment.) This type of UV can also be harmful, and can cause severe burns and cataracts, so caution is advised.

However, for many users this may not be a problem, as it is usually only a very light 'straw' shade, and at worst adds a slight warmth to colour Images.

As with other lenses problems encountered may include fungal growth and stuck diaphragms. Provided the fungal growth is slight the lens performance will not be discernibly affected, but cleaning the fungus out is still advisable. Stuck diaphragms are usually due to grease on the blades, which will need cleaning. Both of these operations will require disassembly of the lens.
FWIW I cleared a 50/1.4 in a window (summer in NC) in about 10 days.
I have another one in the window for 2 weeks in the netherlands (winter) and the change is almost imperceptible to me
will wait a few more days


Last edited by titrisol; 02-03-2009 at 02:32 AM.
02-16-2009, 10:46 AM   #9
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QuoteOriginally posted by titrisol Quote
Google is our friend
Disassembly and Cleaning of the F1.4 50mm Super Takumar Lens



FWIW I cleared a 50/1.4 in a window (summer in NC) in about 10 days.
I have another one in the window for 2 weeks in the netherlands (winter) and the change is almost imperceptible to me
will wait a few more days


Well I have to say, I kept my 50/1,4 next to my New England windowsill for a couple weeks and the change was almost imperceptible.

I don't know if that's because of the winter sun, or because the window glass actually cuts most of the UV, as apparently they tend to do :-o
02-16-2009, 02:53 PM   #10
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Window glass (especially modern stuff meant for heat-efficiency) actually *does* cut much UV. Yellowed glass tends to be pronouncedly-so after much time and you may as well bleach it reasonably, anyway. I don't think anything about the process commends haste. I recently obtained a 35mm F2 with a Thorium glass element for my old Canons, (the low level radiation from that is likely to and does yellow coatings if left in the dark a while) and *that* was like looking through an old Kodak gel until a little patient exposure to broad daylight over a few days.

It's not the glass that yellows, or even the coatings, apparently, just what sticks em there. You don't want to introduce any very-rapid changes there. They'll just take a cast, sometimes. Don't try to undo in a hurry what took decades to do.

.
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