A note in servicing Carl Zeiss Jena P 50/1.4 (PB mount) late model

Intro:

Received one Carl Zeiss Jena P 50/1.4 (PB mount) lens. It is one of the unique lenses that truly made by CZJ for Praktica B mount camera. CZJ did make several PB lens for Praktica B mount camera and still they are having high reputation today, and that has reflected on the market price.

CZJ P 50/1.4 could appear like "Carl Zeiss Jena Prakticar", either on the common name ring or on the filter barrel as seen in this website. This website also contains valuable information of other CZJ lenses during the DDR era, worth to book mark:


What I am having on hand is CZJ "P" 50/1.4. Relatively less common I guess? I can't tell whether it is for export, or trying to simplify the naming . If my memory is right, during 1980 "CZJ P" was a very confusing term. There are so many "CZJ" named products but that they are OEM (like zoom lens) , or just from the Pentacon factory (CZJ P 50/1.8 , CZJ P 135/2.8) . Rumors were saying th eformer East German DDR government wanted to use the frame of CZJ to gain income from the hot camera market during that time.




And there is a CZ logo inside, which I never see this on other CZJ P (Pentacon) lenses :


In my copy there is no yellowing on glass and so I believe it shouldn't be radioactive ?

[Progress]

When servicing any PB mount lenses, start with lifting up the inner black ring from ring . For this CZJ P lens it has 2 screws
Then remove the screws on the outer mount . You can skip the short screws under the black ring . Here in my copy there is a shorter screw and underneath is the resistor plate. So, remember , don't mix up with other longer screws

After taken away the metal mount, one should lift up the black base+ aperture index ring as a unit .




All PB mount lenses have this simple carbon vario-resistor installed . It is not a complex , but would definatly painful if the thin wires are broken . Broken wire is one of the causes that the Praktica B mount cameras failed to read Ap value from the lens and calculate the shutter speed in the finder, showing red dot blinking at "Under". Many users have misunderstood it was an defect from the camera.





In this CZJ version , ball bearing is used, which is not seen in other Pentacon made PB lenses.
In most of the time this ball bear are clean and should be free from grease and oil . So one can just leave it alone and not to touch .

The Ap Unit is a sandwich unit, by a Black Plastic Base (facing rear lens group) , thin Brass Driving Ring, metal blades and a metal cover.

A tensioner spring is connected the BDR and the little hook next to the "CZ" logo. Disconnect this spring .

A brass C ring with 3 set screws is used to secure this Ap unit (from the top) and set the largest Ap opening size (f1.4). Loosen the set screws and take out the C ring . Then the Ap unit can be lift out completely.


- Cleaning -

My copy could have been cleaned before, but not completely.
Old oil was accumulated on the BPB and the blade tips end, I believe one could have just used some alcohol in cleaning the Ap blade surface without complete dissemble.



Here is one of the blades (I maximized the contrast and light for better display). We can see the blade was clean on one end, but accumulated on the metal blots ends. It is a common problem when the cleaning of aperture blades did not performed thoroughly.

In this case, the old oil also left marks on the BPB as well .

From my experience, some plastics, paintings, or the coating could have chemical reaction with these old grease/ oil. This is why people often found "stained marks" on Ap blades and plastic parts nearby even after strong cleaning.
Another note is , I also found oil marks on the glass surface of the inner rear lens element, which is closest to the Ap blades. One could have flushed cleaned but ignored the residue on the glass. In other words, one could have a really poor and inexperienced cleaning before.

-Lubrication-
I used graphite on the Ap unit , especially at the joints.
Graphite could always does great job at this type of area. I never lubricate Ap unit with oil or grease.

The whole clean up just took me 2-3 hours. I have spend most on cleaning the glass.

Could you share how to actually get to the aperture mechanism from the front? I'm not sure if I should be trying to remove the whole front barrel or just the nameplate ring - neither wants to turn and I don't want to damage anything by applying too much force in the wrong place.

@kl122002

Thank you for the detailed information!

Thank you very much for your report. It may be useful for other lenses by Carl Zeiss Jena, too. They are quite similar.

The "P" mark could mean Pancolar. Thorium glass was used in Carl Zeiss Jena Pancolar lenses in the early time only ("Zebra" design). Praktica B lenses and MC coated M42 lenses should not contain Thorium anymore.

Sanug said:

Thank you very much for your report. It may be useful for other lenses by Carl Zeiss Jena, too. They are quite similar.

The "P" mark could mean Pancolar. Thorium glass was used in Carl Zeiss Jena Pancolar lenses in the early time only ("Zebra" design). Praktica B lenses and MC coated M42 lenses should not contain Thorium anymore.

Click to expand...

The "P" is confusing for sure.
But 2 identifiable marks on true CZJ lenses are :
- red "4" on the Depth of field scale
-2 black crews on on the inner black ring at the back, just next to the rear lens glass.

The earlier PB mounted CZJ 50/1.4 are also in thorium glass and they are all wisky-like yellow/brown.

sednoid said:

Could you share how to actually get to the aperture mechanism from the front? I'm not sure if I should be trying to remove the whole front barrel or just the nameplate ring - neither wants to turn and I don't want to damage anything by applying too much force in the wrong place.

Click to expand...

The copy on my hand is not complicated. Just unscrew and then I saw everything . It is very straight forward and so I didn't take any pictures .
The front lens comes off as a single complete unit, 3 set screws secure a C brass ring , the AP unit is just right below.
All steps are just like what I have mentioned.

If you have never tried repair any lens by yourself , then I would suggest you better leave it to experienced technicians shops to help.
**The metals inside are soft**. I have repaired a twisted focusing holding arms of a 35/2.4 (aka Flektogon , but in CZJ Prakticar name) because the previous user didn't loosen the hidden set screw first.

kl122002 said:

The copy on my hand is not complicated. Just unscrew and then I saw everything . It is very straight forward and so I didn't take any pictures .
The front lens comes off as a single complete unit, 3 set screws secure a C brass ring , the AP unit is just right below.
All steps are just like what I have mentioned.

If you have never tried repair any lens by yourself , then I would suggest you better leave it to experienced technicians shops to help.
**The metals inside are soft**. I have repaired a twisted focusing holding arms of a 35/2.4 (aka Flektogon , but in CZJ Prakticar name) because the previous user didn't loosen the hidden set screw first.

Click to expand...

I've done a few CZJ lenses (among others), all from the M42 era, and there was always some obvious way to open them - notches for the lens tool etc.



But with this one I don't see anything. Here's where I am and I see no way to continue. I even removed the nameplate ring and the outer focusing ring to see if maybe I'm missing something under them but still nothing. There's an opening for a single set screw on the upper black element (which I'm pretty sure should be the one to remove) but the screw itself was missing when I got the lens so someone might have already been inside. But the element just won't budge and I'm starting to suspect it was glued in by some hack... And the aperture is completely stuck open so I really need to get to it.

sednoid said:

I've done a few CZJ lenses (among others), all from the M42 era, and there was always some obvious way to open them - notches for the lens tool etc.

View attachment 389822

But with this one I don't see anything. Here's where I am and I see no way to continue. I even removed the nameplate ring and the outer focusing ring to see if maybe I'm missing something under them but still nothing. There's an opening for a single set screw on the upper black element (which I'm pretty sure should be the one to remove) but the screw itself was missing when I got the lens so someone might have already been inside. But the element just won't budge and I'm starting to suspect it was glued in by some hack... And the aperture is completely stuck open so I really need to get to it.

Click to expand...

......

For my copy, it just like this ( just unscrew) :





After unscrew the front lens unit, you will see the AP blades unit.

In some cases I see a set/lock screw at the end of the upper barrel for sure. Loosen it first.

Hope it helps.

Thanks for your answers. Turns out all I needed was to warm up the stuck element with a hair dryer - there's a tip for anyone in a similar situation
Once that was done the rest was a breeze and I have a working aperture again.

I also have a bit of a contribution if anyone ever comes to this thread for info about working on this lens (as there's not a lot of it on the internet) - I think I accidentally discovered how to fine tune the infinity focus. Once you unscrew the front barrel element, on the inside of the focusing ring (not on the front lens group but below it) there are two rings with notches for a lens spanner. I checked if they're both tight, and the outer one wasn't so I tightened it up a bit but found out that apparently it changed the infinity focus of the lens. Turning the ring the other way, I was able to find proper infinity setting again.

sednoid said:

Thanks for your answers. Turns out all I needed was to warm up the stuck element with a hair dryer - there's a tip for anyone in a similar situation
Once that was done the rest was a breeze and I have a working aperture again.

I also have a bit of a contribution if anyone ever comes to this thread for info about working on this lens (as there's not a lot of it on the internet) - I think I accidentally discovered how to fine tune the infinity focus. Once you unscrew the front barrel element, on the inside of the focusing ring (not on the front lens group but below it) there are two rings with notches for a lens spanner. I checked if they're both tight, and the outer one wasn't so I tightened it up a bit but found out that apparently it changed the infinity focus of the lens. Turning the ring the other way, I was able to find proper infinity setting again.

Click to expand...

Congrads.

It should worth to mention the seal they used. This happens to some old M42 Pancolar or Flektogon as well.
There should be 3 separate lacquer seals seals when the lenses were out from factory, :

• one for the infinty setting ring
• one for the front lens group
• one from the upper-outer lens barrel

However, in some cases that seals could be jut a big seal that bond all rings/threads in there. During the unscrewing process of lens barrels or lens group could loosen the infinty lock and settings.

Personally, in most cases I never touch the infinity set & lock ring of Zeiss lenses, unless it is off. I often found the Zeiss (including those in C/Y mount, Hasselblad, Rollei ) could have some special taste in setting the infinity. Some of them could be set at hyperfocal distance just after the infinity mark by default.