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Old August 9th 07, 06:33 PM posted to rec.photo.equipment.35mm
D.M. Procida
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Posts: 104
Default Pentax 50mm A lens

Nicholas O. Lindan wrote:

[50mm f1.7 Pentax-A]
It's pretty clear that the lock on the aperture ring mechanism is
faulty, and gets stuck just before f11. It can be moved past this by
holding down the lock button (though I can hear a metallic click as it
goes past).
The lock button should stay down until the ring is in the A position,
but it rises after f8. What are the chances of having this repaired at a
reasonable cost, or even of doing it myself?


I am not a Pentax-A expert, but if it is like other bayonet mount lenses
then removing the shiny mounting ring from the back of the lens by
removing 4 (or so) screws should let you slip the aperture ring from the
lens.


That is what I was hoping to hear.

The original grease should be fine for reassembly. If the motion is
grating then there may be bits of sand in the grease or the grease needs
re-distribution. If you need to lubricate (and you don't have the proper
lubricants) then dipping a toothpick in 10W-30 engine oil and touching
it to parts that need lubing is the best 'kitchen table repair'
solution. Don't use WD40/LPS25/3in1/household oil: they all turn to goo
in a month or so.


On a previous lens I used white lithium grease.

Advice worth price charged. I take no responsibility for anything that
goes wrong [but, like everyone, expect full credit for anything that
goes right].


I shall let you know, if I decide to do that.

Daniele