Praktica LB2 fault

beetee_7 · Dec 17, 2018

Got a Praktica LB2 a few months back. Just finished running a roll of film through it and noticed an odd quirk with it. As the film advanced frame to frame, the spacing between the frames increased. The spacing for the last pictures was about 34mm whereas the spacing between the first two frames was normal. As a result, I only got about 26 pictures out a 36 roll. The wind mechanism did seem a bit stiff, but I assumed that might be normal for this camera. Other than that, the camera seems OK. Maybe a bit of light leaking in. The meter also seems to work to a point. Has anyone had film winding issues like this with Prakticas?
Not sure if i will pay someone to fix it, since I have better cameras than this one. Actually, I only bought the camera because I wanted the lens that was on it. Still, if there is a simple fix, I might pursue it.
Ken

AgX · Dec 17, 2018

There is one fault that would show exactly your results:

The sprocket wheel by fault being uncoupled, the take-up spool still working correctly and film-resistance being too low to make it slip in its clutch.
The result being gradually increasing frame spacing.

beetee_7 · Dec 17, 2018

AgX said:
There is one fault that would show exactly your results:

The sprocket wheel by fault being uncoupled, the take-up spool still working correctly and film-resistance being too low to make it slip in its clutch.
The result being gradually increasing frame spacing.

How would I repair this? Is there a exploded diagram or manual that I could use?

AgX · Dec 17, 2018

Have you even checked for such fault???

There is a service manual, but that is of no value for the uniniated.

There are photo-guides on the net.
A wild guess of mine would be a damaged gear. Repairing such would be a major operation and necessitating a donor camera
Another wild guess what be a fault at the disengage of the sprocket wheel. That might be easier to repair.
The gear train of the L-series is different from many other cameras and thus the latter is a viable possibility.

beetee_7 · Dec 17, 2018

If I am interpreting you correctly(and this is where a exploded diagram comes in handy), the shaft that contains the sprockets is loose and doesn't always turn while advancing the takeup spool. There is some play vertically with this shaft. Where the clutch is, I am not certain. By sprocket wheel disengage, I assume you mean the button on the bottom that allows rewinding the film. I can't imagine that there is a damaged gear, unless it is a plastic gear? The camera appears to have been used very little. Hardly a scratch on it. It probably needs lubrication. I am a retired electronic systems tech and have worked on a few electro-mechanical devices over the years. I was contemplating tinkering with this one as a winter hobby. As to photo guides, I could not find anything specific to an LB2, but wonder if some of the other models might be similar?

shutterfinger · Dec 17, 2018

Instruction manual: https://www.butkus.org/chinon/praktica/praktica_lb2/praktica_l2.pdf
Scroll down to the image with the back open identifying the parts.
Place your thumb on 29 - Film Transport Sprocket and apply light pressure while operating the advance lever. Does the sprocket turn smoothly and consistently?
Do the same with 30 - Film Take Up Spool. How much pressure does it take to prevent the take up spool from turning, light, moderate, heavy?

Helios 1984 · Dec 17, 2018

beetee_7 said:
I could not find anything specific to an LB2, but wonder if some of the other models might be similar?

Praktica standardized the production of the L series, from L to MTL5b, it's basically the same camera with less or more options. The only differences of the LB2 are the selenium meter and the selector ring around the rewind knob, everything else should be the same.

Here the guide I used to open my Praktica L.

also, you might be able to find useful information in the archives of the "Classic Camera Repair Forum" (A gold mine).

summicron1 · Dec 17, 2018

is the drive gear actually pushing? This might be as simple as the rewind button being stuck in and the wind-up spool is doing all the work -- with the camera back open, advance the film and put a finger on the drive gear -- it should push firmly against your finger as it advances 8 sprockets. If it does not, or if it rotates backwards easily, then your rewind button/mechanism is stuck. Take the bottom off the camera and see if it's something obvious.

AgX · Dec 17, 2018

beetee_7 said:
If I am interpreting you correctly(and this is where a exploded diagram comes in handy), the shaft that contains the sprockets is loose and doesn't always turn while advancing the takeup spool. There is some play vertically with this shaft. Where the clutch is, I am not certain. By sprocket wheel disengage, I assume you mean the button on the bottom that allows rewinding the film. I can't imagine that there is a damaged gear, unless it is a plastic gear? The camera appears to have been used very little. Hardly a scratch on it. It probably needs lubrication. I am a retired electronic systems tech and have worked on a few electro-mechanical devices over the years. I was contemplating tinkering with this one as a winter hobby. As to photo guides, I could not find anything specific to an LB2, but wonder if some of the other models might be similar?

Yes. With many cameras when activating the disengage button, the complete transport gear-train goes idle, only the shutter cocking being still engaged. Thus allowing both, rewind as well as double-exposure.
With the L-series though only the sprocket wheel is disengaged. Faulty constantly remaining disengaged (with resp. button in or out) would yield your artefact

beetee_7 · Dec 18, 2018

shutterfinger said:
Instruction manual: https://www.butkus.org/chinon/praktica/praktica_lb2/praktica_l2.pdf
Scroll down to the image with the back open identifying the parts.
Place your thumb on 29 - Film Transport Sprocket and apply light pressure while operating the advance lever. Does the sprocket turn smoothly and consistently?
Do the same with 30 - Film Take Up Spool. How much pressure does it take to prevent the take up spool from turning, light, moderate, heavy?

- It doesn't take much pressure on the film transport socket to stop it moving - very light pressure. In fact it does not engage at all unless you apply light vertical pressure on it. Even then, it will slip easily. It takes a lot of force to stop the take up spool from moving.

beetee_7 · Dec 18, 2018

AgX said:
Yes. With many cameras when activating the disengage button, the complete transport gear-train goes idle, only the shutter cocking being still engaged. Thus allowing both, rewind as well as double-exposure.
With the L-series though only the sprocket wheel is disengaged. Faulty constantly remaining disengaged (with resp. button in or out) would yield your artefact

One of the first things I did after noticing the fault, was to remove the bottom plate and inspect the the innards. I was surprised to see how simple the construction was compared to some other cameras I have examined. I did not see any obvious faults, and no pieces fell out. It was very dry and clean. I did not want to tear it apart anymore without asking some questions on a forum. When I get a chance I will open it again and observe how the sprocket wheel is functioning.

AgX · Dec 18, 2018

First thing to check would be the disengaging mechanism on whether to have turnerd into constantly disengaging.

Sorry, I still have not really started working on my L-series samples, thus I can't be of further help. But maybe some other member chimes in who has hands-on experience

chuck3565 · Jan 4, 2019

AgX said:
First thing to check would be the disengaging mechanism on whether to have turnerd into constantly disengaging.

Sorry, I still have not really started working on my L-series samples, thus I can't be of further help. But maybe some other member chimes in who has hands-on experience

This is a common problem with L series cameras. The plastic inside the sprocket chips when someone tries to force the film advance lever at the end of the film roll. Usually it can be repaired by cutting a round piece from the plastic top of a can of nuts the size of the sprocket bottom. Hole punch a hole in the center of the piece the size of the sprocket axle and cut a line from the outside of the piece to the center hole. Push this piece under the bottom of the sprocket until the center hole surrounds the sprocket axle. Now when the film advance is wound, the sprocket shouldn't slip.

Praktica LB2 fault

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