Warming problem with JOBO CPE-2 Plus

Discussion in 'Darkroom Equipment' started by egfp-stamp1, Apr 10, 2006.

  1. egfp-stamp1

    egfp-stamp1 Member

    Messages:
    3
    Joined:
    Apr 10, 2006
    Shooter:
    35mm
    Hi,

    I just unpacked and turned on my CPE-2 Plus and it looks like there is a warming problem. It just warms up very slowly and it actually never reaches 38C.

    I was pressing overheating protection button few times but it doesn't help.

    When I turned on the processor without water the heating wire warms up very quickly and becomes very hot after few seconds (Don't worry I stopped the machine), so why is it so slowly with the water???

    I was waiting like half of a day and it reached maybe 35C! (the red lamp is all the time on)
    Is it normal?
    Or should I contact JOBO for reparation/regulation?
    (the motor works well in both directions)

    I would also like to know what are those two plastic wires which are attached to both branches of metal heating wire? Are they some temperature detectors? Maybe they shouldn't be co close to the heating wire as they may show wrong (too high) temperature?

    Thanks a lot for any help
     
  2. grahamp

    grahamp Subscriber

    Messages:
    973
    Joined:
    Mar 2, 2004
    Location:
    San Francisc
    Shooter:
    Multi Format
    What is your room temperature? If it is < 15C the heater may have trouble raising the temperature _and_ combating heat loss.

    Try using hot water to fill the tank and see if the system can maintain 38C. It should stabilise and cycle on and off. Do not assume that the temperature control markings are accurate. The element is intended to cycle on and off so that the temperature approaches the setpoint gradually and does not over-shoot.

    It is normal practice to have the sensors right next to the heating element in water baths. Since the CPE-2+ does not have a circulation pump the most accurate peak temperature is near the element.
     
  3. Ronald Moravec

    Ronald Moravec Member

    Messages:
    1,266
    Joined:
    Jan 17, 2005
    Location:
    Downers Grov
    Stir the water occasionally if there is no pump.

    Stand the unit on a piece of styrofoam to keep from loosing heat to a sink or countertop. This has helped mine considerably.
     
  4. egfp-stamp1

    egfp-stamp1 Member

    Messages:
    3
    Joined:
    Apr 10, 2006
    Shooter:
    35mm
    Thanks for answers!

    The machine did keep 38C the whole night when I started with 40C water, but the temp. falls immediately if I open the window.
    My general conclusion is that the temperature keeping mechanism is very inefficient!
    I don't know how this machine is supposed to keep like 0.5C precision???

    Another problem is the temperature inside a drum - I'm sure it will be few degrees lower than the water bath temp! Just because most of the drum volume is anyway in the cooler air. Also drum is made of plastic - it will not aquire water temp quickly and effectively (bad heat ductor)
    That's why I have a next question - maybe all chemicals should be kept at ie. 40C (and not 38C) so that they lower their temp. to 38 when inside a drum?
    (also only pouring them into a drum will cause immediate drop in temp!)

    I'm new to such machines so I don't have any practice.

    Thanks for any help.
     
  5. Bob F.

    Bob F. Member

    Messages:
    3,984
    Joined:
    Oct 4, 2004
    Location:
    London
    Shooter:
    Multi Format
    My darkroom is usually at 20-22C and my CPE2 has no problems maintaining 38-40C. When running at a high temperature I set my CPE2 to 1C above the temperature I need as the developer will fall by about 2 degrees as it runs in the tank. Test yours first with water to see what temperature drop you get over the development time.

    The machine maintains +/- 0.5C precision thanks to the wonders of the high specific heat capacity of water and its consequent thermal inertia...

    If you turned it on with no water in the tank before you first used it, it is possible that you damaged the heating element - Jobo specifically say that doing so will damage the machine.

    Don't rely on the temperature dial settings: use a calibrated thermometer. I use two: one in the water and one in the developer bottle. Swish the water around every now and again to keep the two temperatures the same.

    Place the film in the tank and spin it for 5 minutes on the CPE2 before putting the first chemical in; that way you bring the tank and contents up to temperature before the chemicals go in. If you have the lift mechanism, things are quicker and timing more accurate but if you don't have the lift and have to lift the tank out of the water bath to fill it, do so as quickly as possible.

    If the room temperature falls when you open a window, don't open a window... :wink:

    Have fun! Bob.
     
  6. antielectrons

    antielectrons Inactive

    Messages:
    205
    Joined:
    Jan 26, 2005
    Shooter:
    Medium Format
    Dont trust the temperature dial. You have to use a separate thermometer. ON mine the dial was normally 5-10ÂșC out.
     
  7. pentaxuser

    pentaxuser Subscriber

    Messages:
    8,233
    Joined:
    May 9, 2005
    Location:
    Daventry, No
    Shooter:
    35mm
    I'd endorse what Bob F said. Unless you want to wait for a very long time then don't rely on the element heating water from say 15-16c to 38c. Use water at about 40c then the thermostat will allow it to fall to whatever it is set at. I find the thermostat accurate to within about half a degree but you should use a calibrated thermometer at each end of the tank. Once the right temp is reached, mine stays there to within about 0.2 degrees C. As the tank is rotating immediately above the water and has water in it at say 39c, then the drop in temp over 3 mins 15 secs for C41 is going to quite small. This is especially the case if the film has been spun dry in the tank for 5 mins while you do something else prior to loading with developer.

    pentaxuser
     
  8. egfp-stamp1

    egfp-stamp1 Member

    Messages:
    3
    Joined:
    Apr 10, 2006
    Shooter:
    35mm
    Success!

    Well, I just accepted the reality of inefficiency of the temperature stability and was adding warm water during the process and keeping all windows closed with room heater on (the whole room was like waterbath...) and it looks like I got very good slides!

    I'm very happy. I used 3-bath Jobo E-6 chemicals.

    Thanks.