Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

[ic-racer]

Now that I am using the enlarger I have noticed a loud metal-on-metal squeal when lowering the head. Time to open up the column and have another look inside (I had it apart once but did not see anything unnusual).

Even with it open I could not pinpoint the squeal. So, the plan was to lubricate all moving parts and see if that makes it better.

The vertical screw was moist with oil, so I left that for last (mistake...)

There are a number of ball bearings that act as wheels and center the head apparatus on the 8" round column. Each ball bearing unit has a metal-to-metal contact with the column. Each bearing also has a little felt piece to hold lubrication. The bearings along the bottom of the apparatus have the felt piece mounted on the underneath side. A little hard to oil with a gravity oiler. I decided to use a spray oil that is made for things like motorcycle chains. It is thick and will stick on an underneath surface, but it also penetrates well. It does not evaporate easily, also.

I am not recommending this brand, just documenting what I did. I used Tri-flow. I sprayed all the ball bearings, making sure the felt got soaked also.

It still had the horrible grinding, so I sprayed the lube in the little copper tube that leads to the vertical screw. This solved the problem. It also incresed the speed that the head goes up and down. This little copper tube lines up with a hole in the side of the column panel when the head is all the way down. Therefore, you can supply the lubrication to the vertical screw without having to take things apart. This is covered in the supplement sheet to the owner's manual. (Free pdf for the asking...)

[ic-racer]

The enlarger has the capacity to adjust the height of all 4 wheels. Three of them have milled knobs and the 4th requires a hex driver.

Getting the enlarger level and keeping the same pressure on all 4 wheels is actually somewhat challenging. Durst realizes this and some of the dedicated horizontal enlargers only run on three wheels to make leveling easier.

With adjustments at all 4 wheels it is very easy to make the L1840 run on only three wheels also. (but, of course, this is NOT what you want, because then it will wobble)

I spend a lot of time getting radio controlled cars to have a balanced setup with 4 wheel independent suspension, and have applied some of the same principles to the Durst. Here is my technique.

I use a level along the foot, and level it front-to back. And I also place the level across the feet, to level it side to side. This is not that hard, but it is easy to end up with the weight of the enlarger on only 2 or 3 of the wheels. So, just because it is all level, does not mean it won't be wobbly.

To make sure it won't wobble, you need to make sure the pressure on all 4 wheels is the same. You can do this by twisting each of the wheel height adjusters. Wheels that are in the air and not touching will be easy to identify because the wheel adjuster will twist very easily. If the enlarger is resting on just two wheels, then those two adjusters will be very hard to twist.

So what you may wind up with is two diagonal wheel supporting the entire weight of the enlarger, and the other two diagonal wheels up in the air, or with less pressure. By lowering the two wheels that are supporting the enlarger, you can even the pressure out. In the end you want all 4 adjusters to twist with the same force, indicating equal pressure on all 4 wheels. If your adjusters are rusty...LOL!

After getting equal pressure on all 4, check the level again. It will probably be off, so this whole process can takes some time to get right.

[ic-racer]

I'm not sure of these cooling holes in the top of the Aristo unit. Did they use the same top piece from one of the other units that has the transformer up top? This 1414 unit is special in that it was designed to allow the head of the Durst go all the way to the top with out being higher than the column. To do this they moved the transformer to a separate box. This works great with the Durst L1840, because it has a little tray to hold the transformer.

Anyway, there is a thermostat in the box, so my first impression is to just cover up these holes. I used Electrical tap that is rated to 105 degrees C.

I let the box warm up good and ran the tube for about 5 minutes (the maximium 'on time' they recommend) and the box temp. stayed at about 38 to 40 degrees C.

Again, the reason I want to tape these vents is that they light up the whole room.

[ic-racer]

So, after not thinking about it for a few days I dove back into the power supply. The problem is that the slow UP focus is way too slow. You can almost not even tell the lens stage is moving. The slow DOWN works fine.

There is a confusing graph of the capacitor that bleeds the back EMF voltage so that the speed is constant. The axes are not marked, but once I figured out the Y axis goes from +15 to zero going up I realized there is nothing wrong with the circuit board.

When I put the head horizontal, the UP and DOWN both opeate at the same speed. Again making me think there is nothing wrong.

There is a 'drive time' check, but it requires a 'scope to test. I did think that if the drive time were too short, the motor cannot even start to move before it is pulsed off again. So, I thought I would just tweak the drive time resistor and see what happens. The resistor is number R44 and mine came with a 33ohm resistor in there. It was marked 33 ohms and it measured 33 ohms. The manual says a smaller resistror will increase the drive time, so I swapped in a 10 ohm resistor and.....it worked perfectly!!! So now my UP and DOWN are the same speed and the focusing is much improved. It was so slow before it made it difficult to see any change in the grain.

The third line down in the graph pictured (C5) seems to only make sense with the way the circuit is functioning if zero on the Y=axis is UP. If one interprets the graph as zero being down, then the more load on the motor, the slower the circuit will make it go. This is what I initially thought was wrong, as my motor was going slower under load. But, alas, it works fine now, so I know that they did not build mine backwards

[ic-racer]

Now that I am done fixing it up, I have moved the enlarger into is new home.

[lee\c]

congratulations ic-racer. That is quite a project and I am glad you shared it with us.

lee\c

[ic-racer]

A few notes on my research of this Rodenstock Rodagon 300mm 5.6 lens.

I had noticed glennview selling a Rodagon-G 300mm lens for a premium, so I did some research so see if that lens is better than the one that came with my enlarger.

Specs on the Rodagon indicate it is a 6 element, 4 group lens. The filter thread is 86mm.

Magnification range is listed as 2-8x with 4x being optimum

The Rodagon-G is designed for high magnification. Its range is listed as 8-30x with 20x being optimum.

Both lenses are designed for use with 8x10" negatives.

So, in practical terms the Rodagon will have best performance enlarging an 8x10 negative from 16x20 to 64x80. With the optimum being 32x40. This last size is just about the largest the enlarger will do on the baseboard. With respect to my darkroom, the SMALLEST size range of the Rodagon is the LARGEST print size I can currently process.

What about the Rodagon-G. In practical terms it is optimized to enlarge an 8x10 negative from 64x80" to 240x300" Thats a little big for my darkroom.

An additional note on the range of the Rodagon. As you may know, there is a point where an enlarging lens can no longer form an image. With the 300mm Rodagon, this point is just below the 1:1 magnification level. I tried to do some 1:1 prints and the focusing at this level is very strange. It is difficult to get it in focus, because it is right on the verge of the point where focusing is not possible. I was able to make some 8x10 prints, but compared to contacts, they were clearly inferior. This does show me that to make 1:1 prints, a process lens would be superior.

[ic-racer]

The owner's manual describes the various lensboards that are available, but there are no pictures.

Here are the pictures.

The first one is Unipla. It is like an adapter for the smaller lens plates.
The second one is Lapla. The Lapla comes in different thread sizes, to match different lenses. As you can see the Lapla fits in the middle of the Unipla.

[ic-racer]

The larger lenses, like the 300mm Rodagon, can fit right on an 8" lensboard called the VAPLA. My VAPLA also came with a stalk and a red filter. If I decide to go with 'under the lens' multigrade filters, I will have to make a filter holder, becasue, Durst did not make one. I don't want to destroy the red filter to make it into a filter holder.

glennview sells a replica of the VAPLA for about $200.



Here is a post by someone that found an 8" pan at Wall-Mart that works as a VAPLA:

Posted on Monday, March 11, 2002 - 03:37 pm:
"I recently discovered that I can make the equivalent of a Durst VAPLA lensboard by buying a shallow 8" diameter aluminum cooking pan at WalMart (for $3.88 + tax), and drilling the right size hole in the middle. These pans have a beveled edge, just like the real VAPLAs have. In fact, I'm tickled at the discovery. "

The first picture is the real Vapla and the second is the one that you can get from glennview.
I don't have a picture of the Wall-Mart pan, but I would like to get one so that I can make an adapter like the UNIPLA, that will hold the lens cones and boards from my Omega enlargers. This way I can put the 150mm on and enlarge 4x5s.

[lee\c]

I have a 5x7 Durst 138s and it did not have any of the lens boards for my enlarger. I bought 3 off ebay for 5 or 7 dollars a piece and I took them to a machine shop that is located across the street and they enlarged the holes to fit each lens I wanted to mount.

lee\c