According to a date stamp on the inside surface of the bottom cover, this camera was manufactured in June, 1960. The camera has a simple construction and mechanism, but it can still teach us, amateur repairers, a thing or two. So, let 's take it apart and examine it closely.
We usually begin with taking off the top cover. Open the camera's back door and grab the film rewind fork with one hand to prevent it from turning, while you unscrew the rewind knob with the other hand. Once this is done, we turn our attention to the film advance lever on the other side...
This is a little bit tricky. The diagram on the left will help by presenting a preview of the components we will find in this part of the camera after disassembly. The key to the understanding of what needs to be done is found in the area the red arrow points to. Here we see a shaft with a hole in its top end. The inside of this hole is right threaded, while the outside of the shaft is left threaded. When you take out the screw in the middle of the film advance knob, you can remove the film type reminder disk, but will not get any further. (I'm sure that was a disappointment, if you have already got this far before reading these instructions.) Now you see that the film advance knob (and lever, because, for our purposes, they still comprise a single component - don't try to separate them yet!) is screwed onto this shaft.
Since the shaft is left threaded, we would have to unscrew the film advance knob clockwise. However, there is a problem with this; the film advance lever gets in the way - it won't let you turn the knob. Do not force it, because you will damage the mechanism that is hidden inside the knob (see later). The only other option we have is to turn the shaft, or rather, the film take up spool that is attached to the shaft. (The direction is from left to right.) The danger with this, however, is that the little pin that slots in between the two prongs of the shaft's fork is not too strong and might bend or break. Therefore, be careful. (Especially, if someone already tried to remove the film advance knob and turned it the wrong way, thus tightening it really hard.)
It is also important that we carry out the above manoeuvre just after releasing the shutter and with the rewind release button pushed to the R setting. The reason for these measures will become clear from a description that follows further on.
As you carefully (!) raise the film advance knob and lever combo, you will see that it is still attached to the body with a long spring. This spring pulls back the film advance lever after each stroke. Unhook the spring from the underside of the film advance lever ring.
The next step is to take off the film rewind release button. (This is a small shiny semi-spherical object near the T and R marks.) There is no slot in it for a screwdriver, so we need to take hold of it with a piece of rubber and unscrew it that way.
Finally, we just need to remove the two little screws from either side of the top plate and it will come off.
With the top removed, the camera's entire mechanism - save the shutter - is revealed in front of our eyes. Here we find the components that implement the automatic film counter, double exposure prevention, and film rewind stop / release functions, which make the Beirette quite a smart little machine in its class.
The picture above helps explain the working of the film advance and shutter release mechanisms. The letters indicate the following components:
A stem linking the shutter release button with the shutter's release lever. The shutter fires when you push down on it. A little less discernible is another rod (going down through the body) which moves in parallel with this stem, and plays a role in locking the shutter release button after each exposure.
The film advance shaft. It is coupled with the film take up spool. Notice the threads on the inside and outside.
Small disk-like object which acts as the 'governor' of the mechanism. It rotates in conjunction with the cogwheel below it, which in turn is moved by the perforation on the film when it is advanced to the next frame. (This design is very typical of German cameras.)
Shutter release button locking arm.
L-shaped part whose sharp end on the right hand side hooks into the film advance ratchet and prevents it from turning. (Currently it is disengaged.)
Claw to ensure the rotation of the film take up spool is from left to right, only...
...unless pushed aside with this film rewind lock release lever.
This arm advances the film counter disc. (The film counter disk has been removed).
By the way, the long spring hanging down loose is the film advance lever return spring.
The picture depicts the situation just after an exposure, when the shutter release button has been locked, but the film has not been advanced to the next frame, yet. Thus, we can now wind on the film. As the film moves forward, it turns the wheel whose cogs are engaged with the holes in the film's perforation and also rotates the small disk I called 'governor' above. This has a pin sticking out of it which at first, in its 12 o'clock position, pushes a part forward resulting in D jumping out of a slot in A and, thus, freeing up the shutter release button. As C keeps turning, in its 9 o'clock position it shoves H to the left, making the counter disk jump to the next digit. Finally, C returns to its 7 o'clock position, where the left end of E now falls into the recess on C and its pointed right end swings in between the teeth of the ratchet. (This prevents any further film advance.)
It is a desirable feature of film winding cranks to allow the user to advance the film with several short strokes rather than one (potentially large) swing. Well, even though the Beirette is only an inexpensive camera, it possesses that feature. How did the constructors implement this? To answer this question, let 's take the film winding assembly apart. This is what we get after unscrewing two screws:
A hair-spring pushes a claw against a ratchet and the claw's tip gets caught in between the cogs when the lever is wound from left to right. This forces the knob (and the shaft to which it is attached) to turn. However, when the lever travels in the opposite direction, the claw skips over the cogs (while making a rattling sound).
After the removal of the camera's top, let 's turn our attention to other areas...
It is relatively easy to separate the lens and shutter assembly from the camera body, however, a special tool, called spanner wrench, is required. In its absence we can try using a pair of long tweezers and hope the retaining ring is not fastened too tightly. The retaining ring (see picture below) is accessed from the back of the camera through the film gate and unscrews in the normal manner.
Once we hold the lens in our hand we can play with the shutter and realise that it does not need to be cocked, because it is of an 'eveready' type. Therefore, the film advance mechanism is indeed nothing more than just that. And the reason the shutter cannot be released sometimes is not due to it not being cocked, but a locking device on the shutter release button.
As its name suggests (Trioplan), the lens consists of three elements. Two of these is located in front of the shutter and the third behind it. It is easy to remove the front and rear lens elements (for instance, for cleaning). Again, to unscrew the retaining rings, we should ideally use a spanner wrench, but maybe a pair of strong tweezers will do. It can be observed that, when we focus the camera, only the front lens element moves. Inexpensive cameras often implement this type of focusing. Warning: if the aluminium distance scale ring (which is held by three small setscrews) is removed, the infinity position can only be restored later by measurement. Infinity is not necessarily at the point where the lens is fully screwed in.
The bottom of the camera is held by only two screws. We can easily take off the bottom, although we won't find anything interesting under it. The shiny front plate around the lens is secured to the bakelite body casting with four screws. To access these, the leather has to be peeled up along the sides of the front panel a little bit. After all this is done, the larger, frame-like front of the camera can be pried off the bakelite core.
The black 'nose' of the camera (to which the shutter is affixed) can also be removed (but what for?). It is attached to the body with four screws - two at the top, two at the bottom. We can only get to these after the camera's top, bottom, and front are all removed.
My last bit of advise; don't tighten the screws too hard when assembling. After all, bakelite is not as strong as metal.