Quote Originally Posted by Greg Blank View Post
Bi directional rotation is required for paper processing and smaller film drums. For Expert drums it is not required, I've tested this myself in practice finding no difference in the results of developing sing PMK developer.

I asked the question of the CEO of Jobo USA when the product distribution was being turned over to Omega Satter. His statement was that no, the Expert drums were not required to use it or for that matter designed to require it.

After working on many many CPP2's over four years time, I am lead to believe that the bi directional motion weakens the motor circuit if one is using an Expert series drum, furthermore a overly filled Expert drum.

What I do find required is the need to periodically lift the drum and insure that the chemical and water goes behind the sheets to wash off the anti halation backing. So I raise my drum once per minute for this purpose and turn the motor off while the drum is up and on once its back down.
Greg,

I've been uneasy about what you posted, so last night I looked in the Jobo manual and instruction sheets for more information. (I have yet to find a single instance where Jobo's manual is incorrect, though I am sure than one can use these machines in ways other than what Jobo envisioned.) In Jobo's instruction sheets for the Expert drums, it specifically says that the bidirectional switch should be turned on for normal use. I fail to see how the Expert drums would work differently than the smaller drums in terms of liquid flow. I think the idea behind the bidirectional rigmarole is to avoid streaks cause by unidirectional flow, similar to the need to slosh chemicals in different directions when tray processing. Also, the drums are made to use one liter or less; if someone uses more than a liter of liquid, they are asking for trouble. That is why, when using XTol for example, you need to limit how much you dilute a stock solution. If you dilute XTol more than 1*1, you risk not having enough actual developer within the one liter maximum. At the same time, there is a definite problem with the small motors in Jobo's processors. The company obviously was not able to fully retrofit the processors for the long-term power demands of Expert drums. Since the processors work terrifically well otherwise, we are all left with doing whatever we can to keep them operational.