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#11
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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..... |
#12
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Pentax 50mm A lens
"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 |
#13
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Pentax 50mm A lens
"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". |
#14
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Pentax 50mm A lens
[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 |
#15
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Pentax 50mm A lens
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 |
#16
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Pentax 50mm A lens
"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......:^) |
#17
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Pentax 50mm A lens
"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. |
#18
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Repairing a Pentax 50mm A lens (was: Pentax 50mm A lens)
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 |
#19
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Repairing a Pentax 50mm A lens (was: Pentax 50mm A lens)
"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 |
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