Yashica Atoron (non-Electro) Repair (Minox Type)

[ic-racer]

The non-Electro Atoron comes apart similar to the Electro version. Remove the threaded inserts at each end of the camera just like the Electro. Then remove the film chamber door release lever and film chamber door.

There is a micro ring-nut. I made a special tool to remove it. The nut was also glued in place. Seemed neither acetone or alcohol did a good job softening the glue.

 

[ic-racer]

Unlike the Electro, the EV/Meter wheel needs to come off, along with the frame counter reset knob. The shutter release stays in place.
If you set the meter to "B" it will simplify re-timing the wheel. Note the wavy washer goes between the solid washer and the ASA dial.

 

[ic-racer]

After separating the shell from the mechanism, the front plate is held on with three screws (two on the viewfinder end and one on the opposite end) just like the Electro.
On my camera there was a rectangular spacer between the faceplate and the camera body (red arrow).

My built-in yellow filter (not found on the Electro) was very dirty. To free the filter, remove screws (green arrow) and spring (orange arrow).

I thought my yellow filter had permanent damage, but it did clean up nicely by scrubbing with cotton swabs and alcohol.

Use this opportunity to clean the back sides of the protective lenses over the viewfinder and taking lens,

 

[ic-racer]

In my case the taking lens was perfectly clear and clean on both sides. If you need to get to the back of the lens, cock the shutter and this releases the pressure plate (green circle). The pressure plate is only held on by the sliding cocking mechanism, and can be easily removed. Note the orientation of the spring on the back of the pressure plate when re-inserting.

With the pressure plate off, you will have access to the back of the taking lens.

 

[ic-racer]

On my camera the escapement was sluggish, making all the speeds too slow. There was no good way to measure this, I could just tell. Also, the escapement made a buzzing sound like a mechanical self-timer that I thought was not right.

 

[ic-racer]

The escapement comes out after removing these two screws:

 

[ic-racer]

Removing the larger screws on top of the escapement allows the gears to be removed and individually cleaned. Note the position and orientation of the gears. On re-assembly, the medium gear in this picture needs to be flipped the other way and is the last gear to be inserted.

Note the Jewel Bearing (purple) for the flywheel. This is the first time I have seen a Jewel Bearing in a camera. Indeed this is similar to watch repair!

 

[ic-racer]

After cleaning and re-assembly, I carefully lubricated the pivots, taking care to not get any oil on the gears.

 

[ic-racer]

Two screws on bottom allow the viewfinder to be removed. It is an Albada style. There was some rotted foam on the top front part that I removed and did not replace.

My galvenometer was free to move so I suspected the selenium cell was shot. The cell seemed to be glued in place and I did not disturb it. Maybe some day replacement selenium cells will become available. Until then, I'll just use an external meter.

The lens elements of the viewfinder (four maybe) were all glued in place. Mine was a little cloudy and I took an alcohol soaked piece of paper and fed it between the elements to see if the fog would easily be cleared and there was no effect. That suggested permanent damage so I just cleaned the two outer surfaces and was happy.

In an extreme case the whole viewfindder could be disassembled but the individual element's spacing seemed to be set, perhaps with some jig during gluing as there were no slots for the elements to fix their relative positions for an easy re-assembly.

 

[ic-racer]

Reassemble opposite of disassembly. Make sure all the inner lens surfaces are clean and free of fingerprints and dust before putting it all together.

I used oil sparingly on the rotating gear's shaft (yellow arrow). I used ceramic grease on the film advance lever (green arrow) and on the aperture/speed cam levers (orange arrows).

 

[ic-racer]

All done. The shutter, by sound, is much improved. It clearly is much faster and quieter. Previously the slowest speeds would hang up and B did now work.

Now all speeds, including B, appear to work fine. The viewfinder is still a little cloudy, but not bad really.

 

[ic-racer]

The Atoron (non-Electro) has a wheel with EV numbers that is used to set the exposure by match-the-needle. Since the needle on the meter no longer responds, the wheel can be set to an EV number based on a hand-held meter.

This chart shows how the EV settings on the camera's dial affect both the shutter speed and aperture at the same time. The way it works is the shutter is actually a rapidly moving aperture with two blades. At the fastest speed, it only opens in the middle (f16). At the slowest speed it opens all the way (f2.8).

Again, this is radically different than the Minox. Walter Zapp, would not allow these small apertures (there is no aperture mechanism on a Minox).

 

[ic-racer]

Although the lens on the Electro allows estimation focus (like a Minox), the lens on the non-Electro is fixed focus.

Interpolation of this table shows the focus point is set about 3.5 meters or maybe 12 feet.

 

[tjwspm]

A great guide! This motivates me to give it a try with my Atoron in the next few days. I've been meaning to do this for a long time, but I couldn't figure out how to open the case. Thanks!

 

[tjwspm]

Unlike the Electro, the EV/Meter wheel needs to come off, along with the frame counter reset knob. The shutter release stays in place.
If you set the meter to "B" it will simplify re-timing the wheel. Note the wavy washer goes between the solid washer and the ASA dial.

Today I started dismantling one of my two Atorons following your instructions.
Now I have removed the shell and the front plate. Next I will take care of the escapement, as the times are running much too slowly.

Without your instructions I wouldn't have made it this far. Thanks again!

 

[tjwspm]

Although the lens on the Electro allows estimation focus (like a Minox), the lens on the non-Electro is fixed focus.

Interpolation of this table shows the focus point is set about 3.5 meters or maybe 12 feet.

View attachment 358998

Some time ago I combined the two tables for practical use of the Atoron. So you immediately have the preset combination of exposure time and aperture as well as the associated depth of field (in m) for each exposure value.

 

[ic-racer]

That is great!

 

[ic-racer]

I have been going through all my selenium meters to try an see if any can be rejuvinated. I did find a loose connection in one of them, so I went on a rampage to see if any others could be fixed by checking connections.

So, I did disassemble my Atoron again to fiddle with the selenium cell.

 

[ic-racer]

There is only one wire connected to the selenium cell. There is enough slack in the wire so the whole assembly can be slid to the left, toward the taking lens. The reveals the two screws one needs to take out so the whole assembly can be removed.

 

[ic-racer]

My galvanometer works, but I could not get any response from the cell. I tried re-soldering the wire and scraping the back to get better contact with the camera body to no avail.

 

[ic-racer]

I'm thinking of getting some of these to try. Only $3.

 

[ic-racer]

It seems most on e-bay have a non functioning meter. I did see one with a working meter but the price is pretty steep.

 

[tjwspm]

As mentioned, I have two Atorons of the same (non-electronic) model. I inherited one from my father, who treated himself to it for his 50th birthday in 1970. It is the Atoron, rebranded in Germany as Porst KX50. This camera works like it did on day one, including the selenium light meter.

I bought the second one last year for 20 euros. It is an heirloom from a family living in Germany with Japanese parents who bought the camera in Japan. I opened this camera today because the shutter speeds don't work. Also, the light meter is dead.

 

[ic-racer]

That is nice to have one with a working meter!

Yes these Yashicas were also called Porst and Revue Mini-Star. I used those search terms looking for accessories. I'd like a tripod adapter and right-angle viewer.

 

[tjwspm]

Now I measured the shutter speed at EV 16. It should be 1/250. I measured 1/30. So way too slow.

By the way, after removing the pressure plate, it was very easy to place the light sensor behind the lens. You can see in the photo where I routed the cable.

All measurements
EV: shutter speed
8.5: 1/73
10: 1/10
11: 1/12
12: 1/12
13: 1/20
14: 1/16
15: 1/25
16: 1/30

So, I'll clean the escapement. Afterwards I will measure again to check whether it has helped.