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12-01-2018, 04:17 PM   #1
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Pentax 67 TTL Prism - cannot remove diopter eyepiece

I have the Pentax TTL prism viewfinder.

I cannot turn the knurled ring that holds the diopter eyepiece in place. I understand from the manual that it is supposed to unscrew anti-clockwise, but mine is stuck fast. Any tips on how to remove this? Thanks.

12-01-2018, 04:38 PM   #2
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Give the ring a squirt of WD-40 and let this penetrate for a few minutes.
Then unscrew. Afterward, wash the ring and lens thoroughly in soapy water and dry.
12-01-2018, 04:48 PM   #3
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If it's stuck too hard, try leaving the finder in a warm (~37°C/~100°F) spot for a longer time, then putting something really cold against the knurled ring and using something out of rubber (needs good traction) to unscrew it.

12-01-2018, 07:58 PM   #4
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I would be very concerned if, for some well-intentioned reason, the ring was secured with Loctite - uncommon but also not unheard of! The danger is that the use of force can easily strip the soft aluminium threads on the prism and/or the ring. I would try the least aggressive attempt at removal before anything else.


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645d, 645z, camera, diopter, eyepiece, medium format, pentax, pentax 67 ttl, prism, ttl, ttl prism
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