Jobo 3006 problems

[Robert A. Zeichner]

I took the plunge and bought a 3006 expert drum to process 5x7 negs on my Unicolor roller base. Most expensive piece of plastic I ever purchased! I had no problem loading the film and even made a very effective fluid reservoir to enable me to drain chemicals directly into the drum while it is rotating. At first, I thought the results were great, but then after further inspection, discovered small triangular shaped areas about the size of my thumbnail and located about 3/4" from the shorter edge of the film that were under-developed. Thinking that the problem might be related to differences in rotational range, I intentionally ran a batch in which I lifted the drum off the base for half a second to "advance" the orientation of the drum with each cycle. Same problem. So, has anyone had a similar experience and more importantly has anyone come up with a solution to the problem?

[Ed Richards]

I use a 3006 for 4x5. These are issues I have seen:

Are you sure you are getting the film in with the emulsion facing the inside of the tube? This would be #1 on my list, having done it wrong once.:-) I think this will do what you are seeing.

Which end of the drum are these on, or are they on both ends, i.e., on both ends of the film? Are they are on all sheets?

How much developer are you using?

How are you reversing the rotation?

BTW, I found that just pouring the chemicals in and then putting the drum on the roller worked fine.

[Robert A. Zeichner]

Ed, Yes, emulsion faces inward. The under-developed area is toward the base of the cylinders. I'm using 15 oz. of straight D-76. The Unicolor roller base reverses direction automatically at the end of each rotation (micro-switch activated. I beleive).

[Chuck_1686]

Are the areas hard edged? Maybe you're getting some overlap. I do know that you are probably not turning a full turn if you use the Unicolor reversal switching but you should have covered that when you did things by hand. I normally use 1000-1500 ml when I use a similar system. Maybe you could do a test with say 30 oz of developer. The problems I've seen are small areas along the long edge where the film back didn't quite clear. I run the film through a tray of Permawash to clear and wash outside the drum in hangers. Seems to only happen with Tri-X. Maybe it moves more in the cylinder.

[Ed Richards]

First, turn off the auto reversing - as Chuck points out, you are not getting a full turn, and you need more than that to be safe. Better to just run it in one direction and flip the drum every couple of minutes by hand. Or don't, I do not think reversing is necessary.

It should be plenty of developer. Are you pre-soaking?

[Robert A. Zeichner]

Yes, I do a pre-soak for 6 minutes. This is based on experiments done by others. I never knew there was a way to defeat the direction change switch. Thanks for the suggestion, I will check that out tonight.

[Ed Richards]

Warning - do not open the case unless you are a home electrician type.:-) And make sure you are plugging into a ground fault detector outlet - my experience with this old darkroom stuff is that electrical safety was not always on the designer's mind. I do not know how this model is wired, but there will be some way to defeat the switch. It is probably driven by an arm on the drive wheel - you can remove that and it will not flip the switch any more.

[Chuck_1686]

I can't recall exactly but you can disable the switch. It's a mechanical function and can be done without removing wiring. I changed my Unicolor with some electronics so it turns 2 revolutions before reversing. But easier to just do it by hand. Not sure if this will solve your problem but it will elimate one possible cause.