The Agfa Silette-LK is a vintage camera that operates without a battery, yet it features a semi-automatic light meter. The light meter operates electrically with a selenium cell, and is mechanically coupled to the exposure and ISO film speed setting.
This camera had the problem that the exposure and aperture could not be set individually. As it turns out, these settings were coupled by two plastic rings that were stuck together. The actual repair was simply applying sufficient force to the rings to make them unstuck. The difficulty was in disassembling the camera to get at these parts, so the force could be applied directly. Also, reassembling the camera turned out to be tricky.
Although we did not disassemble all parts of the camera, these pictures should aid anyone who wants to disassemble the same camera model.
There are two ways to access the lense part of the camera: From the back, there are four screws which hold the lense structure to the frame. We did not have the special tool required to remove the top of the camera, but I strongly advise to do that first, because reassembling is very difficult otherwise.
From the front, the focus ring shield can be lifted, revealing three screws holding the ring in place. After removing these screws, the focus ring can be screwed off (you will lose your focus calibration doing this), revealing several layers of interesing mechanics. Note that some of these mechanical plates reach into notches of lower or higher layers (in one case under slight tension). Be careful and do not apply any force here. The stick reaching into that slit from below will have to be pushed back a bit when reassembling.
Lifting the focus ring reveals three screws that calibrate the focus setting. The focus ring base plate has the mounting holes for the focus ring screws. The piece to the right is a spring that pushes against the focus ring (not visible in the picture). This locking spring holds the rest of the lense system in place. It locks tightly around an indented metal ring. I don’t know why it has such a funny shape. This ring sets the ISO film speed. Normally, the lower half grips into a sawtooth line in disc below. Because of the slit, this lock can be released to change the ISO setting. Note the stick mounted at the right side. This stick reaches all the way down into a notch of the plastic ring that determines the exposure and aperture ratio. This disc sets the exposure time. There is a rather complicated spring mechanism underneath. Note that the upper slit gets narrower at the right side, which means shorter exposure time. This shows the shutter system. The gears that transport the film. This mechanism also binds to the shutter release lever. The flash signal lines. Unfortunately, I couldn’t see the mechanism that triggers the flash. The selenium light meter operates without batteries. The electrical current from the photovoltaic selenium cell is strong enough to move a needle on a spring on top of an inductor. There is an opposite mechanical force on the needle from a lever on the exposure/aperture ratio ring. I wonder how this mechanism is calibrated. This ring sets the ratio between exposure and aperture, and is ultimately responsible for adjusting to the ISO setting and nudging the light meter into place. In this repair, the ring was stuck and had to be freed by applying force to the little notch that is visible at the lower right inside the camera, moving it back and forth until all grit is removed from between plastic rings.
