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04-26-2014, 03:30 PM   #1
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Lens Schematic for K55 f2

I just purchased a K55 f2 anndddd the aperture acts up. It doesn't stop down all the way. And the focus feel very gritty. I've been looking for schematics to open it up and see what the problem is but i cannot find any online. Can anyone help?

04-26-2014, 10:23 PM - 2 Likes   #2
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Location: Aurora, CO
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I don't have photos of the K55/2, but from the front it is close enough to the M50/1.7. In the first shot, I've removed the "name" ring, unscrewed via the filter threads. Some kind of rubber grippy thing, like a sink stopper or chair leg protector, helps, as long as it is the right diameter and doesn't touch the front element. The K series might have slotted screws here, or some slotted, some JIS. JIS screws look like Phillips but are not quite the same. A JIS screwdriver is recommended.

If you remove the three screws marked with red arrows in the first photo, you can remove the filter ring and see something like the below photo. The red arrows mark screws holding the focus ring on. The green arrows mark slots for a spanner wrench to unscrew just the front lens group. You can get to the front of the aperture blades doing that. Removing the three unmarked screws will allow you to pull the whole optical assembly out as one unit: front and rear elements, plus aperture.

I'd focus the lens to infinity before removing the focus ring. That will give you a rough idea of where infinity is when you reassemble. If you take off the focus ring, the lens looks something like this:

Removing the front group looks like this:

Removing the optics leaves this:

The optics assembly. The chrome pin goes in the fork marked above:

From the back (mount side), you can get to the aperture ring and the mechanism. The mount screws are usually where that JIS screwdriver is most needed. There's a ball bearing trapped between the aperture ring and lens body, probably just below the orange diamond. The M series lenses are often different at the back. I think the K55/2 is close. I'll show you these shots anyway. Mount removal:

Aperture ring slid off, note the bearing:

Aperture ring:

On the M, the aperture ring is hiding three screws that hold on the rear of the lens body. Remove them and you can pull this off. Inside is the mechanism, springs, etc.:

The M has this washer to link the ring and mechanism together.

There are articles in the repair section on the focus ring, a long topic if you want to unscrew it, clean and regrease.

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