I've still got one A50/1.7 and out of the four I've owned at various stages none have been spectacular build wise.
Rob Studdert
Can you make your way along these?
Andre
The leaf springs that push the A button out will fall off the lens and foul the aperture ring movement. I've repaired it on the A28/2.8. The repair is trivial, the disassembly isn't tough...just keep track of the little ball bearing that makes the clicks for the aperture stops.
Bob S.
The problem associated with the all plastic 'A' prime lenses (and some 'F' lenses too) has to do with the material being chosen, and the structural designs. I tried cleaning and relubricating but only worked for a week or so, then the problem came back. It was better if the bearing was removed, but not exactly a solution. 'A' lenses with metal body + plastic aperture ring are okay (like A50/1.4 or A70-210/4).
Alan Chan
Common problem with the A50/1.7. The aperture ring is plastic, rather than metal
as on the A50/1.4, and it wears readily. Also the springs that tension the "A"
button sometimes break off. They can be reattached, but it 's a bit tricky and
takes some creativity.
Mark Roberts
If you are careful, you can take the aperture ring off and glue the leaf springs down with super glue. The only tricky part is doing it slowly and not looseing the tiny ball bearing that makes the f stops go click.
But you should be handy with small parts and have patience.
Bob S.
What I did to repair mine was to clean all the lubricant from the area with spirits. And then use a slow setting epoxy glue to re-attach the spring making sure that no glue fouled the rotating parts of the mechanism. I'd stay away from cyanoacrylates (ie Super Glue�) as it can foul surfaces whilst curing. Rob Studdert
If you fix this problem, I favor a very, very small dot of JB weld (epoxy) as I always have it around for many other purposes. It too requires that the lens remain unassembled for a few days as with all glues and epoxies, but after 24 hrs there is less out gassing and it will NEVER fail. In addition to being useful to bind things together, this stuff can be used to form parts and can be filed, sanded, milled, drilled and polished. Bob...
I actually drilled a hole where the broken plastic "spike" used to be and re-attached the spring with a tiny screw (how Pentax should have done it in the first place). Mark Roberts
I can strip and rebuild a BMW 3.0 liter inline 6, I can balance the carbs on a 12 cylinder E-type Jaguar by ear, and I can diagnose and repair almost any photo lab problem, but those darned A series lenses don't like me at all. William Robb
