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Biotar 75 - front section / elements disassembly ?
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PostPosted: Tue Apr 14, 2009 8:09 am    Post subject: Biotar 75 - front section / elements disassembly ? Reply with quote

Hi all. Wondering if anyone might have some information about disassembling a Biotar 75 from the front section? It appears from the back, the furthest one can get is to the preset aperture ring. I'd like to remove a little dust internally.

Regards,


Kelly.


PostPosted: Wed Apr 15, 2009 2:47 am    Post subject: Reply with quote

I've done this on my late "fat" Biotar. Its quite easy.

I don't recommend it unless you have a significant haze problem. A bit of dust probably doesn't justify it.

The key is a tiny screw on the black barrel just above the preset ring, its opposite the red triangle aperture mark. Loosen that and the filter ring unscrews, etc.


PostPosted: Wed Apr 15, 2009 5:34 am    Post subject: Reply with quote

luisalegria wrote:
I've done this on my late "fat" Biotar. Its quite easy.

I don't recommend it unless you have a significant haze problem. A bit of dust probably doesn't justify it.

The key is a tiny screw on the black barrel just above the preset ring, its opposite the red triangle aperture mark. Loosen that and the filter ring unscrews, etc.


Thanks Luis. I should have just PM'd you to start with, heh. I did take out the little screw on one copy and gave an uncertain, yet firm twist but to no avail. I wasn't sure that was the trick, thanks. I'll try again.

Truth be told, I have two copies here, of which I am assembling a 'super' version using the cleaner glass from the Exa version with the compatible M42 mount. I've tried this in easier ways, first switching the mount back caps. The Exa fit on both Biotars, the M42 back was only able to fit on its original Biotar. So I moved up the chain, I moved the helical ring over. This time, the ring from the M42 version fits either lens, but the ring from the Exa only fits its original helical. Therefore, I can swap the M42 ring and thus mount cap over to the rest of the Exa, but then the remaining Exa version would not thread to the M42 body. I could stop here and sell the rest of the parts seperately, but I want to go another step with this first.

Fwiw, I've discovered I'm a lot more patient than I used to be and the results of my efforts have been positive thus far. There appears to be some tiny white hazy spots on an element in the 'back-up' glass block I'll address while going into the top. It may result in my not needing to swap the parts to start with if I can clear it up.

Thanks again. For now...


K.


PostPosted: Wed Apr 15, 2009 5:51 am    Post subject: Reply with quote

Hmm. I haven't been able to move it a smidge. Assuming turning the topmost filter ring section is correct, the one copy appears really stuck down. Might I ask you to elaborate when you the chance Luis?

Many thanks,


K.


PostPosted: Wed Apr 15, 2009 8:59 am    Post subject: Reply with quote

Don't risk this lens!


PostPosted: Wed Apr 15, 2009 1:18 pm    Post subject: Reply with quote

Attila wrote:
Don't risk this lens!


I'm cautious and patient. I'm not worried about the result Smile Once I'm finished, both lenses will be cleaner and have smooth operating helicals. When I received my second copy, the helical was so tight it would turn itself off my screw adapter before it would rotate, but now it glides with ease. The last person in there used bad grease and way too much of it.

Since I was bored, I just snapped a pic of the (now clean) helical ring part. As above, the ring shown beside the lens is from the M42 version and fits both lenses and receives either mount cap. The ring on the Exa one only fits on the Exa lens and only takes the Exa mount cap. My mind hasn't gotten around how this is possible...



On the lens


PostPosted: Wed Apr 27, 2011 12:13 pm    Post subject: Reply with quote

nice Wink