Jobo CPA-2 rotation speed control question

Discussion in 'Darkroom Equipment' started by ZoneIII, Mar 27, 2008.

  1. ZoneIII

    ZoneIII Member

    Messages:
    261
    Joined:
    Jan 7, 2007
    Location:
    Illinois
    Shooter:
    Large Format
    I bought a virtually new CPA-2 processor. It' is the latest version with the upgrades. (It's serial number is above 23,000.) The original owner bought it but never used it. While getting familiar with its operation before processing my first batch of E6 film, I noticed that drum rotation speed doesn't increase at any setting over "3." Today I tested it using a small single-roll 35mm drum and also with an empty Expert 3010 drum and then with 500ml of water in the 3010 drum. The tempering bath was filled to the proper level.

    I set the processor to run continuously in one direction for the test. Suprisingly, there was very little difference in the speeds when using the 35mm drum and the filled 3010 Expert. Even more suprising, if anything, the 3010 when filled actually rotated slightly faster than the 35mm drum!

    Here are roughly the speeds I get:

    F - 35 rpm
    3 - 66
    4 - 72
    P - 72
    6 - 72
    7 - 72

    There were some variations but those numbers are pretty accurate. Again, the rotation was actually FASTER with the filled 3010 drum. Maybe the machine was just warmed up or something. But the point is that I'm not getting any speed increase above the "3" setting. Has anyone else experienced this? If so, did it turn out that the Rotation Speed control needed to be replaced?

    Lastly, I removed the four screws on the control panel hoping to be able to lift it off and see if there might be a loose connection to the speed control but the panel didn't want to come off. Maybe it just needs a little force to crack a seal (?). Has anyone removed that panel and, if so, how?
     
  2. eumenius

    eumenius Member

    Messages:
    768
    Joined:
    Jan 6, 2005
    Location:
    Moscow, Russ
    Shooter:
    Medium Format
    How very strange! I was having yesterday an issue alike with my used CPP2, with its motor running faster than described for older motors (in fact, I think, my unit has a new motor). The bulletin about motor upgrade (http://www.jobousadarkroom.com/faq/CPP_Speed_Settings.html) tells that there would be no speed increase after "4" setting. Just consider the behavior of your machine as a normal one, and run your ExpertDrum on a setting between "F" and "3" (50 rpm), and 2500 series on "4". That's exactly the conditions for my machine.

    I am pretty sure that the drive control circuit board should have some kind of potentiometer to control the speed, but it's easier to use the machine the way it already is - with some attention to its built-in quirks.

    Regards - Zhenya
     
  3. snallan

    snallan Member

    Messages:
    524
    Joined:
    Sep 28, 2007
    Location:
    Cambridge, U
    Shooter:
    Multi Format
    The rotation speed controller does appear to be functioning badly. The speeds should be approx 25 rpm at the 'F' setting, 50 rpm at the '4' setting, and 75 rpm at the 'P' setting.

    I have never had to open the control head, but Jobo publish electronic versions of their instruction manuals, and technical bulletins here, if you wish to try opening it up.

    If the speeds are consistent, you could run the expert drum at the '3' setting (Jobo normally recommend a rotation speed of 50 rpm for the expert drums), and the 15xx/25xx/28xx drums at the recommended 'P' setting.
     
  4. ZoneIII

    ZoneIII Member

    Messages:
    261
    Joined:
    Jan 7, 2007
    Location:
    Illinois
    Shooter:
    Large Format
    Zhenya,

    After posting the question, I found a forum where this very thing was discussed. It turns out that even Jobo's data shows that rotation speed will not increase after the 4 setting on machines with the newer motor and upgrades. My tests today showed that I got a rotation speed of about 50 rpm with the dial set just past the "F" setting. So your advice correlates with what Jobo says and what I have found with my own maching. In other words, it's normal. So, as you say, I'll just use it that way it is. Before finding that thread, I thought that maybe my potentiometer was bad. Makes one wonder why they even have settings past "4" on the machines with the newer motors!

    Anyway, it's good to know nothing is wrong. Thanks much!
     
  5. eumenius

    eumenius Member

    Messages:
    768
    Joined:
    Jan 6, 2005
    Location:
    Moscow, Russ
    Shooter:
    Medium Format
    Steve, read that bulletin concerning the new motors: http://www.jobousadarkroom.com/faq/CPP_Speed_Settings.html

    ZoneIII says that his unit has this upgrade, so it should be 46 rpm on "F" and 70 rpm on "3".

     
  6. snallan

    snallan Member

    Messages:
    524
    Joined:
    Sep 28, 2007
    Location:
    Cambridge, U
    Shooter:
    Multi Format
    Yes, I had'nt seen that faq, my cpa/cpps have the old motors, so I was going from memory. :smile:
     
  7. eumenius

    eumenius Member

    Messages:
    768
    Joined:
    Jan 6, 2005
    Location:
    Moscow, Russ
    Shooter:
    Medium Format
    Yes, Jobo made a BIG mistake not identifying this all-important change to their machines more openly. I also thought that my CPP2 works wrong because I have developed a bucketful of E6 slide in my 3010 on ~80 rpm, so the machine had some troubles with it :smile: After I checked the REAL speeds, I was pointed by APUG people to the bulletin, and everything became clear for me at once. Let's just run the machines at 'F-3' for Expert, and at '4' for all other tanks - this will do okay, and the motor won't be strained.

    Good luck!

    Zhenya

     
  8. ZoneIII

    ZoneIII Member

    Messages:
    261
    Joined:
    Jan 7, 2007
    Location:
    Illinois
    Shooter:
    Large Format
    The "P" setting would be a bit fast for my machine. It may have produced 50 rpm with the older Jobos, though. Here is a link that mentions it. http://photo.net/bboard/q-and-a-fetch-msg?msg_id=004trY

    I also found another thread that I just can't seem to find again where other's reported the same thing that I am experiencing - no speed change above the 3 or 4 setting. Some responded with Jobo's own data which is no longer available at the Jobo site. It showed the speeds do not change after the "4" settings on processors with the new motors. Also, the speed settings that do work with the new motors produce different rotation speeds than older Jobos. If I can find that info again, I will post it here. The point is that a speed setting on an older Jobo will not be the same as it is on the improved models.
     
  9. eumenius

    eumenius Member

    Messages:
    768
    Joined:
    Jan 6, 2005
    Location:
    Moscow, Russ
    Shooter:
    Medium Format
    I think that someone will find and read it only when he notices that the machine works just too fast :smile: And I even think that many motor failures of Jobo machines are related to this issue - people kept running their loaded ExpertDrums on recommended "4" setting, while it's almost twice as fast as recommended! Thanks Jobo for their care :smile:

    Zhenya

     
  10. eumenius

    eumenius Member

    Messages:
    768
    Joined:
    Jan 6, 2005
    Location:
    Moscow, Russ
    Shooter:
    Medium Format
    That's what the link (http://www.jobousadarkroom.com/faq/CPP_Speed_Settings.html) is all about, of course. The P setting on newer machines is too fast for any process, leading to increased oxidation and strain on machine. What was the reason to do it that way - maybe Jobo was simply unable to change control circuitry to keep the drive in bounds specified before? :smile:

     
  11. ZoneIII

    ZoneIII Member

    Messages:
    261
    Joined:
    Jan 7, 2007
    Location:
    Illinois
    Shooter:
    Large Format
    eumenius beat me to it! I just looked at his link and it is the actual Jobo page listing the differences between rotation speeds between old and new processors. (Thanks, eumenius. I'm going to save that because Jobo is taking more and more stuff down from their website.) As you can see, the newer machines do not increase in rotation speed after the 4 setting. They increase slightly from the 3 to 4 setting which is what I found with my machine. And consistent with Jobo's data, I found that I achieve 50 RPM when my speed control is set slightly over the "F" setting. It's nice to know that my new machine isn't defective.

    Thanks everyone.