Jobo Processors

[1750Shooter]

I have three questions about Jobo processors: are the tanks available to handle 5x7, is the rotation speed constant for all developers or does it change, & finally, what is the speed if it is constant? I have the ability to make the rotary mechanism & not the finances to buy it, but would like to try rotary processing. Any other duggestions would be appreciated. Thanks in advance,

[Michael Graves]

To do 5x7, you need an Expert drum. The 3006 is designed specifically for 5x7, but I have had success in a pinch developing 5 5x7s in a 3010. I've read where others had developing problems doing that, but I've done it several times with no ill effect. For an Expert drum, you need a CPA or CPP processor. I've heard about people using print drums to develop negatives, which would permit the use of a CPE processor. I cannot personally address that, because I've never tried it. Rotation speed on the CPA and CPP is adjustable. I'm not sure about the CPE. I personally don't let the tank reverse. I just let it rotate constantly. Again, no ill effects that I've been able to see. I use rotation speed 4 for all developers. The speed you select will affect the overall density that highlights will attain, but in the long run, once you calibrate to a particular developer, time, temperature and rotation speed, your results will be incredibly consistent. Try and couple of different speeds and pick the one you like.

[muihlinn]

Expert drums are designed to be used at 50rpm, so they are used at that speed whatever the process is. Rotation reverses each few turns. Design it to do not stress the motor with 1 liter loads.

[Kevin J. Kolosky]

"I have the ability to make the rotary mechanism"

Could you make some further comments on that. What do you have the ability to make?

[Jim C.]

You may want tot try to locate a copy of The Rotary Processing Manual by John Tinsley
it's Jobo specific and might have the info you're looking for.

[koh303]

As noted above:

the ideal 5X7 drum is the Jobo 3006 drum for up to 6 sheets of up to 5X7 (you can do 4x5 as well).

The easiest way to use this drum and by far most economical is the Jobo 1509 roller base, with which you manually rotate the drum.

Otherwise, as noted, the drum should be rotated about 50rpm regardless of process, and reversed direction every two full revolutions.

[1750Shooter]

It seems as though the rotary mechanism is a simply roller drive with a timed reverser. Not too difficult to fabricate using surplus computer electronics, nylon for bearings, & some plywood for the housing.

[koh303]

It seems as though the rotary mechanism is a simply roller drive with a timed reverser. Not too difficult to fabricate using surplus computer electronics, nylon for bearings, & some plywood for the housing.

Those are famous words posted by many before you but none as of yet have ever actually came through - i am eager to see what you come up with - GOOD LUCK - keep us posted with your results!