Pentax 50mm A lens
 

Paul Mitchum wrote:

Just got one of these from someone on eBay. Is it correct that to move
the aperture ring beyond f11 requires depression of the button on the
ring? On my 28mm ring the button is only required for the A position.

The button lets you use the A setting. If the aperture ring won't go
past f/11, then it might be time for repair.

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?

[Followups set]

Daniele

Pentax 50mm A lens
 

D.M. Procida wrote:
Paul Mitchum wrote:

Just got one of these from someone on eBay. Is it correct that to move
the aperture ring beyond f11 requires depression of the button on the
ring? On my 28mm ring the button is only required for the A position.
The button lets you use the A setting. If the aperture ring won't go
past f/11, then it might be time for repair.

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?

[Followups set]

Daniele

Personally I'd have a go myself, but you might not be as keen to take a lens
apart. The cost of repair would outweigh the cost of replacing it from eBay.

Did the eBay listing say it was faulty? If not then you are entitled to return
it and get a refund.

Pentax 50mm A lens
 

Richard Polhill wrote:

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?

Personally I'd have a go myself, but you might not be as keen to take a lens
apart. The cost of repair would outweigh the cost of replacing it from eBay.

I repaired a fairly similar Praktica lens, but I had less to lose as
that was non-functional - this lens is otherwise perfect, and works
beautifully in all other respects.

If there were some way to get at the lock mechanism without messing
about with the focus screw, I'd certainly go for it.

Did the eBay listing say it was faulty? If not then you are entitled to return
it and get a refund.

I'm in touch with the seller, but exploring options.

Daniele

Pentax 50mm A lens
 

Pentax 50mm A lens
 

Tony Polson wrote:

Bearing in mind that you are in the UK, a reasonable cost to repair
this lens would be about GBP 30 to 40. However, that is probably a
lot more than the lens cost you. Doing it youself might be an option,
but inexperienced hands can do a lot of damage to a perfectly good
lens.

Personally, I would return the lens to the seller and demand a refund,
then find another example that doesn't need work.

I would strongly recommend that you should look for an SMC Pentax-A
50mm f/1.7, which is one of the best 50mm lenses ever made for an SLR
of any brand.

That is indeed the one. I got it for less than £40, including postage.
It's a really excellent lens, and takes great pictures.

Daniele

Pentax 50mm A lens
 

[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.

Cover your workplace with a fluffy white towel to catch any dropped or
sproinged
parts - look out for little ball bearings used to generate the 'click' on
the
aperture ring.

The good news would be that something slipped and fitting it back (possibly
with
a little gentle corrective bending) fixes everything.

The bad news is that something inside has broke in two. The most cost
effective
solution is to remove the whole lock-button assembly/parts - the lens
aperture
won't lock but the lens is perfectly useable.

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.

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

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index.htm
n o lindan at ix dot netcom dot com

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

Pentax 50mm A lens
 

D.M. Procida wrote:

Paul Mitchum wrote:

Just got one of these from someone on eBay. Is it correct that to move
the aperture ring beyond f11 requires depression of the button on the
ring? On my 28mm ring the button is only required for the A position.

The button lets you use the A setting. If the aperture ring won't go
past f/11, then it might be time for repair.

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).

I'm coming into this thread late so I may have missed the specific
A-series 50mm lens being discussed... but I'd guess it's the 50mm
f/1.7 - its aperture ring was made with inferior (probably cheaper)
material than that on the 50/1.4. If your lens is the SMC-A 50/1.7
then this is the likely cause; the indents in the inner side of the
aperture ring just get ground down. Sometimes this can be cured by
removing the aperture ring and giving everything a thorough cleaning
and lubrication. Sometimes this helps enough to make the lens usable.
You *might* be able to do it yourself, but it's easy to lose parts
(especially the ball bearing that clicks into the detents) when
disassembling and really tricky getting everything back together.

--
Mark Roberts Photography & Multimedia
www.robertstech.com
412-687-2835

Pentax 50mm A lens
 

"Mark Roberts" wrote in message
...
D.M. Procida wrote:

Paul Mitchum wrote:

Just got one of these from someone on eBay. Is it correct that to move
the aperture ring beyond f11 requires depression of the button on the
ring? On my 28mm ring the button is only required for the A position.

The button lets you use the A setting. If the aperture ring won't go
past f/11, then it might be time for repair.

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).

I'm coming into this thread late so I may have missed the specific
A-series 50mm lens being discussed... but I'd guess it's the 50mm
f/1.7 - its aperture ring was made with inferior (probably cheaper)
material than that on the 50/1.4. If your lens is the SMC-A 50/1.7
then this is the likely cause; the indents in the inner side of the
aperture ring just get ground down. Sometimes this can be cured by
removing the aperture ring and giving everything a thorough cleaning
and lubrication. Sometimes this helps enough to make the lens usable.
You *might* be able to do it yourself, but it's easy to lose parts
(especially the ball bearing that clicks into the detents) when
disassembling and really tricky getting everything back together.

If you do lose the ball, this place has a huge variety of them...
http://www.vxb.com/ballbearings.html...FSA4hgods24arQ

Pentax 50mm A lens
 

If you do lose the ball, this place has a huge variety of them...
http://www.vxb.com/ballbearings.html...FSA4hgods24arQ

Other sources are industrial supply distributors:

http://www.mcmaster.com/
pg 3566 "Metric Stainless Steel Balls"

a very good source for all sorts of stuff...

--
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121