Durst L1200 Magnification Grip Slips

[Cor]

Hi,

I have this 20+ years old Durst L1200 Laborator (condensor version) which has been working flawlessly. Recently I noticed a small problem with the hand grips you use to raise and lower the head:

Seen from the back: Grip A is for the fine adjustment, B dislodges and is used to move smoothly over larger distances:

127961

The problem that grip A does not function any more, ie the head does not move when turned.

A closer look reveals this:

127962

So Grip A drives chain C and a metal disc, which has a black disc (of rubber or ? material) attached to it, which is supposed to take a long metal disc E which drives the Teflon gear for the fine adjustment.

As I judge is :this black material is worn, become smooth, and does not "pick" up the metal disc E by friction any more (I assume that a clutch works along these lines, not to well versed in mechanics).

Is this the cause, and is it repairable (with not too much effort and difficulties) ?

thanks and best,

Cor

[Richard Wasserman]

I am wondering if maybe the mechanism has gotten dirty over time and needs a good cleaning or perhaps the belt has stretched and should be replaced. Am I correct to assume that nothing can be adjusted?

[Cor]

Hi Richard,

The distance between the belt and the metal disc which it should engage (right phrase?) is only 1-2 mm, so cleaning is hard I guess, the grip B pushes both metal discs together by a flat thin metal strip/spring, which pushes out the disc C to the right towards disc E. Can just be seen. This spring can presumably adjusted by the 2 screws at the front, next to letter C, they are however covered in red stuff, probably not to be touched ?

Thanks,

Cor

[Richard Wasserman]

I have the same enlarger, but so far have not had this problem. You can clean with an electronic spray cleaner which should be available at an auto parts store. Something like this— http://tinyurl.com/q479fre You might need to re-lubricate the chain, I think with white lithium grease you can buy at the same place where you get the spray cleaner. I don't know what to suggest if the belt needs replacing, but I assume they used a common one that is still available somewhere.

I think you're correct about the screws with red stuff (Loctite)—don't touch.

Good luck!

[ic-racer]

What I don't know from the manual and pictures: Does the locking knob act through that clutch or does it lock by some other means. You seem to indicate the head can still be locked. So, I suspect the clutch a 'slipper clutch' that allows the head to move up and down without wildly spinning the fine adjustment knob?

If that is the case then the screws with red on them could be adjustment screws for the mechanism.

[Cor]

Hi IC Racer

Truth is that I actually don't know when it stopped working, I usually use grip B, which is actually more of an Off (move head freely) On (fix head) knob by turning up or down. Mostly that is enough to get the right magnification, so in the past the fine adjustment grip A worked fine, but somewhere I changed habits. Recently I did not get there easily by just B and wanted to use the A grip, just than I noticed the slippage (well actually the head does not move at all when using grip A).

Grip A and B "command" the same disc, D. When moving the head freely (B dislodged) D and E are not engaged, but E turns when you move the head up through the teflon gear (grip A does not move than). When you lock the head, D is pressed on E , the head is lock, but not tight enough , if you turn grip A, D moves through chain C, but there is not enough/no grip to get E moving .

Kinda hard to explain, but I hope I made it clear. It's not that the enlarger is beyond operation, I can get by fine, but I always like to have my equipment functional.

On the screws: have to take a good look again, but my enlarger is in a tight place, and getting behind it is not that easy.

Best,

Cor

[angusparker]

I just got one of these and the rail and the big "spring" that goes up and down counterbalancing the head were filthy. I used some Goo be gone and cleaned it up with a paper towel. Much smoother action as a result. I had to remove the back cover and about 4 screws to do it. That may be the issue.

[ndrs]

I've never opened mine, nor had problems with it, but seeing those plastic gears there really made me worry...

[Richard Wasserman]

Yeah, me too.


I've never opened mine, nor had problems with it, but seeing those plastic gears there really made me worry...

[Jim C.]

Cor, the disc ( E ) with the rubber ring looks severely worn to the point of seeing the reinforcing cords in the rubber.
Is there something inside that may be scraping against the rubber on ( E ) ?
For something like that to wear down to the point of seeing the reinforcement doesn't make sense to me on an enlarger.

Is Durst still in business ? it may be worthwhile to call to see if they have a replacement part

[Sevo]

Cor, the disc ( E ) with the rubber ring looks severely worn to the point of seeing the reinforcing cords in the rubber.
Is there something inside that may be scraping against the rubber on ( E ) ?
For something like that to wear down to the point of seeing the reinforcement doesn't make sense to me on an enlarger.


That is no sign of wear, the cords get exposed as the rubber sheet is cut into discs. If there should be wear, it will not be on the edges (which don't touch anything) but on the surfaces (this is a friction disc). In my experience, there is no wear proper, but the surfaces harden until the friction drive slips - so far I managed to cure that on mine by sanding down the rubber disk. If that should eventually wear it down, it should not be that hard to find a suitable rubber sheet to cut a replacement from.

[ic-racer]

That is no sign of wear, the cords get exposed as the rubber sheet is cut into discs. If there should be wear, it will not be on the edges (which don't touch anything) but on the surfaces (this is a friction disc). In my experience, there is no wear proper, but the surfaces harden until the friction drive slips - so far I managed to cure that on mine by sanding down the rubber disk. If that should eventually wear it down, it should not be that hard to find a suitable rubber sheet to cut a replacement from.

I replaced a similar slipper clutch on take-up spool of my Bolex movie projector with rubberized cork and it works well.

Also, the more I look at the pictures, it looks like the two adjustment screws are to adjust the friction on the mechanism.

[Cor]

Thank you guys for the feedback so far !

I am not worried at all about the teflon gear and the rack and pinion (?) rails it grabs, they look still perfect.

IC-Racer, I indeed think I'll first gently try to adjust those 2 screws.

Sevo: if adjusting those screws does not work, I will give your approach a try. Is the disassemble as straight forward as it looks ? I guess I will first secure the head with a large belt to the base board so it it will not "jump" up.

Thanks again,

Best,

Cor

[Cor]

Ok,

Updating an older post of mine; I tried to clean rubber friction disc "D" by sparsely spraying some pure ethanol over it, and use tissue paper to clean it. Now the grip "A" works again, so it drives through C, D and E the fine focus again, but now I have the opposite problem: the grip B does not dislodge the friction disc any more, guess the ethanol made some gooey matter on the surface of the rubber disc.

So if I raise or lower the head the whole mechanism (A/B connected to C/D) spins/runs.

Am I right in assuming that this does not matter too much since the white (telflon) cog wheel and rack and pinion rails (right of E) are always engaged anyway. The dislodge grip B is there only to move the head up and down faster and smoother ?

best,

Cor



Hi,

I have this 20+ years old Durst L1200 Laborator (condensor version) which has been working flawlessly. Recently I noticed a small problem with the hand grips you use to raise and lower the head:

Seen from the back: Grip A is for the fine adjustment, B dislodges and is used to move smoothly over larger distances:

127961

The problem that grip A does not function any more, ie the head does not move when turned.

A closer look reveals this:

127962

So Grip A drives chain C and a metal disc, which has a black disc (of rubber or ? material) attached to it, which is supposed to take a long metal disc E which drives the Teflon gear for the fine adjustment.

As I judge is :this black material is worn, become smooth, and does not "pick" up the metal disc E by friction any more (I assume that a clutch works along these lines, not to well versed in mechanics).

Is this the cause, and is it repairable (with not too much effort and difficulties) ?

thanks and best,

Cor

[kngkc]

Hi, recently I was given a L1200, my issue is the handle B does not lock the enlarger head to the column. The counterweight pulls the enlarger head all the way to the top. Does anyone has a solution please. Thanks