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

  1. #11
    ic-racer's Avatar
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    Knowing (or believing to know) the exact problem with the power supply, I continued with assembly of the enlarger.

    I have started to work on the cold light. I opened it up and it has the W45 lamp that I can use for multicontrast printing (Yeh!). The number is printed right on the glass tube.

    I just set the coldlight on top of the enlarger and did a dry run to get a feel for how high the column needs to be to make a 11x14 or a 16x20. This picture shows the position of the head, table and lens stage for a focused 16x20 print (300mm lens, 8x10 negative).

  2. #12

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

    Sweet...space:-) Thanks for sharing this great adventure. So is that the highest position the head will go? what is the maximum size print it can print with the 300mm lens?

    Robert

  3. #13
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    Quote Originally Posted by fuegocito View Post
    Sweet...space:-) Thanks for sharing this great adventure. So is that the highest position the head will go? what is the maximum size print it can print with the 300mm lens?

    Robert
    One good thing about the coldlight vs the Durst color head is that the coldlight will allow the enlarger to go all the way to the top of the column and still have a few inches of clearance!

    With the baseboard all the way down (to 'zero' on the scale) and the head all the way up (until it reaches the automatic stop), an 8x10 negative projects onto the entire baseboard with a few inches to spare around the edges. The baseboard is 43 inches, so I think the projected image is around 40 x 32 inches. This is all with a 300mm lens.

    Since I can only process up to 16x20, I am able to have the baseboard all the way up (to save my back) and still have some room at the top of the column for a little cropping, if needed.

  4. #14
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    Even though I have a tape measure (and know how to use it ) pictures like this had me worried that the enlarger was not going to fit.

    I never knew for sure how much room I was going to have until yesterday when I finally got it wired and plugged in and ran the head all the way up.

  5. #15
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    A few words on alignment. This is the point where I would launch into a multiple-page posting on the fine points of critical alignment.

    Well, I checked the 4 corners of the largest projected image on the baseboard (40x32 inches) and they were all sharp with the lens wide open at 5.6.

    WOW!

    I could get out the laser and check it, but if it is a little off, what am I going to do? It already is sharp on all 4 corners (and center) with the grain magnifier, and that is the gold standard for me.

  6. #16

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

    Thanks for sharing! I used one of these (and other big Durst's and DeVerre's) in the eighties and ninties at a pro-lab, and they are great machines, I tired to make that most ours went to good homes when it was "time".
    All we have now is a bunch of computers!
    Keith

  7. #17
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    While eating lunch I saw a RadioShack and recalled that they still sell a few ICs. I went over to check and of the ten or so chips they sell, one was a quad OP amp with pin locations that matched perfectly! SoI replaced the OP amp chip (for $1.25), but the new chip also gave 'faulty' results. Hmmm.... maybe it is me that is faulty.

    So, I re-read as much as I could on Op amps and it turns out the inputs don't subtract from each other if a certain one of them is larger than the other.

    Then I was off changing resistor values to get the reference voltage on the one pin of the OP amp to be lower than the other. This did not work, it just lowered both voltages.

    Then I realized the I was misreading the scale on the voltage graph. Well, there is NO SCALE on that graph, but it looked like the voltage needs to get way beyond 13.8 volts. The way it gets there is by charging the little capacitor (C5). To get this to charge IC6 (a SPST solid state switch) needs to turn on. This is not turning on because the counter chip (IC5) is dead.

    I was ready to replace the counter chip, when I saw on it's data-sheet that the CLOCK pin on this chip is not a clock output. It is a clock INPUT! So where is the blasted clock to run this chip? I had been under the impression the counter chip (IC5) had a built in clock. I searched all over the board for a 555 timer chip and there is none.

    The counter input leads to the logic circuit for telling which button is pressed. Hmm, do you have to keep pressing the buttons on-and-off to get the counter to work? This had me puzzled.

    Then I traced out one of the logic circuits and they are using a positive feedback loop to get one of the logic circuits on IC3 to oscillate. This looked burned out, as it was not oscillating. There are a resistor and capacitor in the circuit to slow it down (it's supposed to oscillate at 600Hz) so I lowered the resistor value and the thing took off to 7K Hz.

    At this point all things down stream started working and the slow button was now working!!!

    I spent about 3 hours soldering and unsoldering various resistors to get it to oscillate at 600 Hz, but it was very unstable. The frequency was all over the place.
    The capacitor checked out OK, so I suspect the logic IC3 is near its end of life and I suspect that if I replace IC3 the oscillations will be more stable and then can be fined tuned back to 600Hz. So, at this point I am 99.9% there. BTW the new IC3 chip is a whopping 26 cents! ($4.00 shipping, though )

  8. #18

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

    Quote Originally Posted by ic-racer View Post
    While eating lunch I saw a RadioShack and recalled that they still sell a few ICs. I went over to check and of the ten or so chips they sell, one was a quad OP amp with pin locations that matched perfectly! SoI replaced the OP amp chip (for $1.25), but the new chip also gave 'faulty' results. Hmmm.... )
    I am so glad my old Elwood 810 does not have any electronic bits in it, my level of handiness is that the world falls apart if a screw and nut does not match...

  9. #19
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    At this point I am not sure if I am going to keep the coldlight. It looks like it has the W45 lamp which is not suited to VC printing. I guess all I would need to do would be to get a new lamp and some VC filters, though I suspect these two purchases may be more than the enlarger cost ($20 each for the filters and $350 for the V54 lamp). I suppose I could just do it the old fasioned way and use graded paper and do all the contrast control with a spot meter and variable negative development time.

    While I am trying to figure that out I wanted to give the power supply a good work over.

    The power supply is just abox with a big transformer for 480V inside. The transformer says it was made in Hong Kong in 1978. I tried to open the lid but it is filled with tar or something.

    There was also a 'mistry box' with three wires coming out of it.

    Opening this up I found a 240V relay. This will allow the 240V timed output from the Durst to control the coldlight.

    To eliminate some of the cords, I re-mounted the relay inside the coldlight supply. This also let me mount a 3 way switch on the coldlight supply. Now I have ON, OFF, and DURST TIMER. With this setup it can be used like any other coldlight in the ON positon, or it can be controlled with the 240 v relay in the "DURST TIMER" position.

  10. #20
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    Re: Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

    Here is the coldlight power supply with the relay mounted inside. I also shortened the cord to the Durst so that it is only about one foot long.

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