I was shooting in a cave in Sri Lanka I took 3 pictures on a tripod, and this is the last of the 3. 

In the upper right hand corner is a shadow with some kind of purple streak. This is the first time something like this happens on my Pentax K-x, and never happened again. Is this a sensor problem or static electricity discharges of some kind ?

This is a crop of the image. 

I posted it at the pentaxforum.com. A member there think that it is a violet shirt. On closer inspection the shadow do looks very similar to a t-shirt. Guess I was too busy looking through the viewfinder.

If you just need to calibrate the meter, this is how far you need to go.. Just use the 4 trimmer at the bottom.

For a complete strip down you need to remove the aluminum scale. Remove the 2 screws holding the needle limiter  (B).  Remove the  pin from the rocker switch (B2), so you won’t lose it. Slide the plate carefully. Try not to touch the needle, its quite fragile.

Now remove the 2 retaining nuts (D) holding the board.  Now you could access the whole board.  During reassembly put the high-low selector lever (E) between the spring, then screwing the board to the back cover.

The 2 screws (D) are shorter than the other, make sure you don’t mix them up. Using the longer screws on these positions  will short the plate, the needle will shot to the right all the time.

This is the back of the board. It is attached to the battery compartment by 2 cables. On reassembly make sure the zero adjustment slot (F)  is engaged with the pin on the zero adjustment screw.

Remove the front name plate (A) with a friction tool. As usual I use the rear cap covered with heavy yellow rubber glove. In this copy the ring was stuck, so I dropped a few naphtha, put the front cap and let it sit for an hour.

There is another part under the front plate. It is attached by 3 screws. Remove these screws.

Underneath you will find 3 screws with brass washers. These screws connect the focusing ring with the outer helicoid.  Remove these screws.

Remove the focusing ring. Also remove the DOF scale ring, it is hold together by 3 small headless screws. Now you could remove the aperture ring. Again, be careful of the ball bearing underneath.

With a spanner, remove the front lens group (A).

Now separate the aperture actuating assembly by removing the 3 screws on the barrel.

If you need to relube the helicoid or accessing the aperture blade, remove the 2 tabs (A) each held by 2 screws.

The lazy aperture was not caused by oil on the blade. It turned out that by loosening the 3 screws a little bit, the aperture was snappy again.

On reassembly, make sure the the position is right. The aperture actuating lever & hook (for I don’t know what to call the F shaped part)  (B)  and the notch and ball bearing spring (C)  are in the same position.

If you need to access helicoids, just turn the brass ring until the the helicoids disengages. To access the aperture blade, you have to remove the O ring with a spanner.

After completely disassemble the lens, the gray thing turned out to be some flaking lens blackening paint.

Note on reassembly

Reassembly is quite straightforward, just reverse the process.

If you remove the helicoids, you need to adjust infinity focus :
A. Asemble the lens until you arrive at step 4.  Mount the lens to a camera with known good focusing.
B. Focus the lens at a distant object. Now mount the focusing ring at infinity position. Attach only 1 screw, don’t tighten too much. Check the focus again, if it moved, loosen the screw and readjust.
C. Put the rest of the screws and tighten.

After removing the 3 screws (A), unscrew the cover (C).  Then remove the 3 screws (B)  to remove the metal part.

This is how the lens lok after removing part (C) in th step 1. Note the aperture detent ball bearing & spring. Remove the spring for safe keeping.

Now you could remove the focus scale. The adhesive tape that hold the 2 plastic rings determine the infinity focus adjustment.

Remove the 2 screws and plastic housing on each side of the lens. After this you could take out the plastic shell. Note I took this picture before removing the focus scale.

On installation, do the infinity focus adjustment as the last step, just before attaching the rubber ring.

Attach the lens to a camera. The idea is to make the focus scale shows the infinity mark when the lens reach infinity focus. Focus the lens to infinity, aim at an object 300 meters away.Then carefully move the focus scale so it point at infinity. Stick a short (~1 cm) adhesive tape  so these tube won’t move against each other. Double check the focus. If everything is fine, then wrap the longer adhesive tape around the tube.

Moving to the front. Remove the front ring with a friction tool.

The screws (A) hold the front lens group.  remove these and then remove the front lens group. Be careful, if these screws are removed, nothing will hold the front group. The position of the group will affect the aperture size. On installation, set the aperture at f2.5, then adjust the position so it just at the largest opening.

Removing screws (B) will enable you to access the helicoids. There are 3 of them. I wouldn’t recommend messing with these unless absolutely necessary.

I took this picture when I need to readjust the aperture size. If you need to access the lens elements or aperture blade, remove part B. The lens elements are all in A, attached with rings. Be careful when removing the middle elements, do it slowly. Mine got stuck in the tube, and I have to use heat to dislodge it.

If you need to access the helicoids, remove the 2 screws  on each side. Note the position. On reassembly, you have to position the helicoids into this position again ie. they all reach the minimum position at the same time.  Mark each release point, and count how many turns needed for each helicoid.

These helicoids should be assembled so they reach their shortest length at the same time.

Reassembly of these part is a spiritual experience.

These are the front groups. The grease on both my copies are still in good condition.

When installing, arrange the rearmost helicoid so the slot for the aperture lever are opposite the ball bearing position.

Remove the 3 screws (A). After this you could lift the both the rear mount (B) and aperture ring (C).  Again, be careful of the spring loaded ball bearing behind the aperture ring. You could also remove the aperture ring later.

These are the parts of the rear mount. There are some washers glued to the second ring.

Remove the 2 screws holding the rear aperture assembly. Note that I haven’t remove the aperture ring (B).

This is the metal hook (A) that hold a spring. In both my copies it is just glued in place. Use a metal hook to remove the glue, then move it so the spring has less extension. You have to experiment on the correct position. Fix the part with glue once it is in the correct position.

I tried it on both my copies. and now both can stop down to  f 32.

Remove the name plate (A) with friction tool the usual way. Make sure the tool will not touch the bulging front element. My favourite tool, a Pentax rear lens cap & rubber glove (C) do this job nicely. Then remove the 3 screws holding the filter selector ring (B).

Once the filter selector ring (A) was removed, remove the 3 headless screws (B) holding the indicator ring. Remove the 3 focus screws & washer set (C), then remove the focusing ring.

Remove the 3 headless screws (A) holding the aperture indicator ring. Also remove the focus limiter screw (B). Then remove the aperture selector ring (C).  As usual, beware of the booby trapped ball bearing.

Remove the 3 screws (A) holding the front and back part together.

To remove the front lens group, first remove the 2 tabs (A), and turn the front group. On reassembly, rotate the front lens group you could :

1. Align the cutout (B) with a piece of metal on the inner side of the back. The metal act as a spring for the aperture click ball

2. Insert the aperture lever  (C – not visible) into the F shaped part of the aperture mechanism (C – not visible)  bearing.

These are the parts after the front lens group was removed.

To access the internal filter, use a lens spanner to remove the front lens group from the helicoid. The internal filters are held in place by metal retainers.

To access the rear lens group elements, remove the filter holder (A), well a friend told me its some sort of filter holder, although I have no idea what kind of filter will fit into this. Next remove the rear cap (B).

Use lens spanner to remove these rings (A & B) if you need to access the rear elements.

Tips on reassembly :

A. Adjust the lens groups so it doesn’t press on the rear aperture assembly. Else the aperture might get sluggish or won’t move at all.

B. Focus adjustment. Put the front lens group to its minimum distance.  Set the 3 focus adjustment screws, but do not tighten them yet. Turn the focus ring to infinity.  If you don’t get infinity focus, loosen the focus adjustment screws and slide the focus ring around.

Remove the 3 screws (A). Then just pull the back casing.

Remove the outer element and shroud (A).   You could remove it later on, but I prefer to work with as little lens element as possible.

Remove the 4 screws holding the focus rod (B). Remove the rod right away.
Remove the focus adjustment screw (C)
Unscrew the end of the casing.

Pull the lens hood (A) and unscrew it. Some might have a small screw, mine doesn’t.

To remove the aperture assembly, unscrew the 3 screws and pull the assembly.

The A/M lever(C)  is connected to a spring (B). Unhook the spring from the post (A).  Then remove the A, C and D.

Unhook the aperture spring (D) first. I use a needle to do it.

Remove the outer collar (A), use a spanner for this. Then remove the inner collar (C)

Remove the aperture rod screws (B)

Remove the inner collar (C) . It is not screwed, you just need to pull it out. Installing it is a bit tricky, because the spring need to be attached first. I use a bit of gue to attach the spring, before installing the inner collar.

Installing the aperture blade is a bit tricky. Install all the items in picture 5.

Position the inner & outer disk so the lever is in this posotion.

Put the inner collar, it has a slot, so it will only goes in in this position. Make sure the outer disk is centered.

Attach the spring to the inner disk’s lever.

Pull the inner disk lever as far as possible to the right. Adjust the outer disk, so the aperture opening match the inner disk’s.

Remove the inner collar, and install the aperture rod.

Then install the inner & outer collar. You might want to install the aperture rod first,but I find it difficult to position the disks with the aperture rod & ring installed.