Durst HL 2501 AF Problems

Hello everyone!

I am stuck between a rock and a hard place really, and I need some help! We (at West Wind Arts) have a Durst HL 2501 AF and a Durst HL 2506 10x10 enlargers. My boss is one of the handful of folks out there still printing on Cibachrome, he is getting to the point after 40+ years of film photography and selling his prints where he has to be very mindful of what he prints still. Today we were making astounding progress on some prints when on the 14th print all of a sudden the print's mid values got ALL out of whack out of nowhere.

The 9th, and 10th prints were good, but we had to add some more developer replenishers mixed some up following Ilfords instructions double-checking along the way all seemed well. Ran two prints through 11/12 and they were honestly some of the best we had done out of this batch of roughly 50 30x40's overall was really excited to finish the printing and move on to another image. Then disaster...

Prints 13/14, look like at the drop of a pin someone added 2 points of yellow to the first printing out of the enlarger and the second looks like it was printed with the f stop completely open. We have gone back and checked the chemistry, repair manual, the machine calibration. And nothing yet. I mentioned the idea of looking for someone to repair the machine but it looks like for about 10 years it's been getting harder and harder to find someone who knows how to fix these machines. I just want my boss to be able to print his legacy and share it with more folks!

If you know of anyone with wiring diagrams, repair knowledge, parts, etc please reach out to us!
Thanks so much

Welcome to Photrio, @Mokubuyo !

That's a tricky problem, given the complexities on both the equipment and material ends of the process. As a consequence, the first thing that comes to mind is the need to differentiate between equipment and material failure. I'd start by cutting strips from the same sheet of cibachrome and doing some tests to see if you can get consistent test strip results. Evidently use chemistry from the same batch for these.

In parallel, you could try doing some test strips also to test for consistency on a different enlarger; perhaps you've got something very simple standing by - basically any dichroic head enlarger with a sufficiently stable power supply should suffice for this kind of test. Use this enlarger to test strips from different sheets of paper to see if there are somehow inconsistenties in the material. Furthermore, since you've got two Durst 25xx enlargers sitting there, the likelihood of both developing similar problems at exactly the same time is rather unlikely, so some testing with series of test strips/prints on both enlargers in parallel would make sense as well.

So in short, before attempting to repair something, try and establish the nature and approximate location of the problem, first.
If the need indeed arises to repair anything on these Durst enlargers - good luck...these are complex machines as you well know and schematics are usually hard to find to begin with, and then you'd still need to track someone down who's willing and able to work on them.

This enlarger?

koraks said:

Welcome to Photrio, @Mokubuyo !

That's a tricky problem, given the complexities on both the equipment and material ends of the process. As a consequence, the first thing that comes to mind is the need to differentiate between equipment and material failure. I'd start by cutting strips from the same sheet of cibachrome and doing some tests to see if you can get consistent test strip results. Evidently use chemistry from the same batch for these.

In parallel, you could try doing some test strips also to test for consistency on a different enlarger; perhaps you've got something very simple standing by - basically any dichroic head enlarger with a sufficiently stable power supply should suffice for this kind of test. Use this enlarger to test strips from different sheets of paper to see if there are somehow inconsistenties in the material. Furthermore, since you've got two Durst 25xx enlargers sitting there, the likelihood of both developing similar problems at exactly the same time is rather unlikely, so some testing with series of test strips/prints on both enlargers in parallel would make sense as well.

So in short, before attempting to repair something, try and establish the nature and approximate location of the problem, first.
If the need indeed arises to repair anything on these Durst enlargers - good luck...these are complex machines as you well know and schematics are usually hard to find to begin with, and then you'd still need to track someone down who's willing and able to work on them.

Click to expand...

Thank you so much!

I just made it back in for the day, we've put together a flow chart for testing as well as comparing changes made right before the issue. Both Durst units are going to be getting tested in parallel today so we can hopefully hammer out some kinks and maybe narrow down where our problem is. We have a repair manual for the machines but a lot of the testing procedures are difficult to follow without schematics to match connector locations and pinouts. Going to call Durst soon to see if they have any old adaptors, test equipment, manuals, schematics, or goblins in the closet that can come out of retirement to fix our moody enlarger.

Happy to be here, hope all is well with you.

ic-racer said:

This enlarger?

Click to expand...

Yes but no!

Small world lol wasn't expecting anyone to pull up a picture. 2506 is working just fine, it's the 2501 we're having issues with, in the image you attached the camera person is standing right in between the rails of the enlarger.

I got the schematics for my L1840/CLS2000 about 15 years ago from DURST in Italy. Even at that time they were closing down support. It took a number of e-mails.

In the end the schematics were not as much help as I thought because all the ICs are just represented by symbols. One needed to look up all the IC datasheets to see what they do (which I had already done before getting the schematics).

List of items I was able to repair on mine:

Bad resistor in Power supply
Fractured wire in ribbon cable to controller board
Fried transistor on motor control board
Unstable 'metastable oscillator' due to ? corrosion on PC board?
Broken switches on control board
Lever re-affixed to shutter
Replaced fried resistor on shutter control board


Some were easy to fix once diagnosed. For example the timer stopped working because the 60hz signal was carried by the outermost wire of the ribbon cable to the controller, which had been run over by the wheels at one time. etc.

With persistence anything can be fixed!

Also, a member of LF forum has or had a HL 2501. From what I recall, he also had some spare PC boards and other spare parts to keep it running:

ic-racer said:

I got the schematics for my L1840/CLS2000 about 15 years ago from DURST in Italy. Even at that time they were closing down support. It took a number of e-mails.

In the end the schematics were not as much help as I thought because all the ICs are just represented by symbols. One needed to look up all the IC datasheets to see what they do (which I had already done before getting the schematics).

List of items I was able to repair on mine:

Bad resistor in Power supply
Fractured wire in ribbon cable to controller board
Fried transistor on motor control board
Unstable 'metastable oscillator' due to ? corrosion on PC board?
Broken switches on control board
Lever re-affixed to shutter
Replaced fried resistor on shutter control board


Some were easy to fix once diagnosed. For example the timer stopped working because the 60hz signal was carried by the outermost wire of the ribbon cable to the controller, which had been run over by the wheels at one time. etc.

With persistence anything can be fixed!

Click to expand...

I was put into a queue earlier when we tried to call DURST up to see if they still had any diagrams lying around but no one ever got back to me. The issue has been resolved for now!

We did some test strips between the two machines with the same lightbox and determined that it was the light bulb that flared up a few times. The one in the machine has been in there for about 6mo, looks like it was purchased a few years back but it had some run time on it already. I know it's almost pointless to ask, but if I were to look for some IC datasheets for the 2501/06 AF any clue as to where I might be able to locate some?

I imagine that next time there is an issue we likely will not be so lucky, called a few people in the community near me to see if there were any resources still out there or people to work on this stuff, but as you can imagine that was a big negative. I know of a few folks in the EU that have the knowledge but finding them is quite the challenge.

Very glad I have stumbled into this community, thank you so very much!

Most all the components will have a number on them and there will be .pdf files available on the internet.

For example, when diagnosing my timer, I tracked down the 60hz signal to this IC and easily looked up the .pdf file on the internet (before I ever got the schematic).