Pentax 50mm A lens

"Nicholas O. Lindan" wrote in message
hlink.net...
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...

--
Yes....The problem I always seem to have when buying such things is that the
manufacturers refuse to sell you one or two items. They want to sell you
several hundred, because they don't deal with individuals, but with jobbers
who operate warehouses full of stuff.....I ran into this, (for example) when
I was trying to replace the valve springs on my flugelhorn with slightly
stronger ones to give my valves slightly faster action. I could measure the
spring force on my stock springs, and pick the springs I wanted to replace
them with from a manufacturers catalog, but then I couldn't get the
manufacturer to sell me only a few springs.....

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

Paul Mitchum wrote:

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



I took one of those apart once, it turned out that the
ball was made of plastic instead of steel. It wore a flat spot and at ome
point would stop rolling and just drag.
Bob Hickey

"William Graham" wrote in message
. ..

"Nicholas O. Lindan" wrote in message
hlink.net...
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...

--
Yes....The problem I always seem to have when buying such things is that
the manufacturers refuse to sell you one or two items. They want to sell
you several hundred, because they don't deal with individuals, but with
jobbers who operate warehouses full of stuff.....I ran into this, (for
example) when I was trying to replace the valve springs on my flugelhorn
with slightly stronger ones to give my valves slightly faster action. I
could measure the spring force on my stock springs, and pick the springs I
wanted to replace them with from a manufacturers catalog, but then I
couldn't get the manufacturer to sell me only a few springs.....
I ran into a similar problem when I needed to replace the fan blades on the
dryer assembly of my RA-4 processor. The manufacturer of the processor
(Hope) is long defunct. The name of the manufacturer of the fan blades was
molded into the plastic. I contacted them. They told me they could sell me
1000 pieces, or they could send me six samples for a $25 handling fee.
Try asking the manufacturer for "evaluation samples".

[ball bearing balls:]
The problem I always seem to have when buying such things is that the
manufacturers refuse to sell
you one or two items. They want to sell you several hundred

That's where McMaster Carr http://www.mcmaster.com/
[and Berg and Grainger] come in - they do sell
one or two items. As ordering one of a 12 cent
item is a bit off-the-wall I usually find something
else I need so the order at least makes the
shipping charge reasonable.

Often a very good hardware store will have assorted
selections of all sorts of odd hardware. Ones that
have been in business for 80 years and have never
thrown anything out are best.

--
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

bob hickey wrote:

I took one of those apart once, it turned out that the
ball was made of plastic instead of steel. It wore a flat spot and at ome
point would stop rolling and just drag.

I'll bet that was someone's make-shift replacement: The originals are
steel.

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

"Nicholas O. Lindan" wrote in message
link.net...
[ball bearing balls:]
The problem I always seem to have when buying such things is that the
manufacturers refuse to sell
you one or two items. They want to sell you several hundred

That's where McMaster Carr http://www.mcmaster.com/
[and Berg and Grainger] come in - they do sell
one or two items. As ordering one of a 12 cent
item is a bit off-the-wall I usually find something
else I need so the order at least makes the
shipping charge reasonable.

Often a very good hardware store will have assorted
selections of all sorts of odd hardware. Ones that
have been in business for 80 years and have never
thrown anything out are best.

But that sounds like my basement.....And I still can never find what I
need......:^)

"D.M. Procida" wrote in
message
...
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


I have examples of both the 50mm f/1.7 and the f/2.0. Compared to my
earlier-generation SMC Takumar lenses, the "A" lenses fall far short of the
mark, in terms of build quality. The effortless movement of the aperture
ring on the SMC Takumars has been replaced with a much harder-to-move
operation on the A lens. The rubber focusing ring on the A lens easily
comes off, unlike that on the SMC Takumars. The Takumars' use of aircraft
aluminum barrels has been replaced with cheaper metal alloys in the A
lenses. Although the A lenses' use of the K-mount is a plus, the lenses
have an overall feel of cheapness, relative to the M42 designs.

Mike Johnston, in one of his articles on Luminous Landscape, said that
manufacturers had learned how to suck the quality out of cameras and,
especially, lenses, in an effort to reduce costs and increase profits. Even
the most superficial comparison of Pentax lenses will reveal that they
cheapened the lenses by a significant margin, between the M42 mounts and the
A series.

And the subsequent plastic-barreled A lenses were even worse. Compared to
the classic M42 examples, the plastic lenses feel like toys.

D.M. Procida 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.

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 have successfully - partially - repaired this.

I removed the lens's mounting plate, then pulled off the aperture ring.
Beware that the spring-loaded ball-bearing will likely fly out (later I
will upload a picture showing where the ball-bearing is).

There is a simple mechanism which locks the ring: two metal leaves which
catch on an indent on the inside of the ring, one for each direction.
One had become unanchored and was pivoting around inside. I wasn't able
to re-fix it securely enough (it was a melted plastic mount, which had
simply broken off), so I just removed it.

The lock still works going into A-mode, but no longer prevents the ring
coming out of A-mode. But that's OK because the indent should stop it
happening accidentally.

I cleaned off the old grease (with plastic crumbs in it) and used
silicone grease to replace it - I couldn't find my lithium grease.

The eBay seller was good about it; I got a partial refund.

I managed to get a tiny smear of grease (possibly just finger oil) on
the rear lens element. What's the best way to clean that?

Daniele

"D.M. Procida" wrote

a melted plastic mount, which had
simply broken off

Sometimes you can drill a hole where the mount was
and insert a metal roll-pin. Use a pin vise for
drilling, not a power drill.

The lock still works going into A-mode, but no longer prevents the ring
coming out of A-mode. But that's OK because the indent should stop it
happening accidentally.

That's often the best repair solution: if it's broke then chuck
it out. Primitive medicine, amputation, but it saves the bulk of
the patient.

I managed to get a tiny smear of grease (possibly just finger oil) on
the rear lens element. What's the best way to clean that?

It's rubbing that ruins lenses and not the cleaning agent. In general
the more powerful the cleaner the less rubbing needed. I use
Windex [I don't know what it is called in the UK, blue stuff in a
squeeze spray bottle for cleaning windows], dip a cotton swab in
it so it is semi-dry and gently wipe towards the center of the
lens till the grease is gone. Change the swab with every swipe or so.
You have to be careful that the Windex with grease doesn't
get under the rim of the lens, where it will stay and slowly creep
out and require re-cleaning till the end of time.

--
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