Your Jobo help/thoughts appreciated

[Peter Black]

I recently bought a Jobo CPE2 complete with a 1520 film tank and a 2840 drum, followed by a 2509 reel for doing E6 4x5. I then sat and waited for a suitable 2500 series film tank to come along at something like a reasonable price.

I then saw a reference elsewhere to removing the bottom part of the 2840 as the 2509 would fit into it, and I've just tried this out. The attached photos show the 2840, then the bottom part detached with a bump in the base, the third one shows the 2509 reel in it and the modified lid, while the fourth one shows the lid in place on the 2840 base.

The lid mod was to take the insert from the 1520 film tank and fit it into the 2840 lid, and I'm assuming that the small chemistry entry pipe will fit into the top of the 2509 centre spindle to make it light-tight, but I haven't tried it yet. The other thing is that I'm not sure if the base bump will prevent chemicals entering/draining or significantly slow the process down.

Given the prices that 2500 series tanks go for, I can't quite believe that the relatively cheap 2840 drum can be used as a substitute, so I'm looking for your thoughts and maybe experiences of this?

Many thanks, Peter

 

[RobertV]

Yes you can build over the Jobo tanks.

One advise: Try to use a 2502 reel and tank for your rotary development.
An elevator makes the whole thing more accurate and much easier in handling. But then you need the cog on your developing tanks.
Especially for short C41 times (3:15 minutes) it's very easy to have.

 

[paul_c5x4]

The mold numbers are the same for both the 2840 base and the 2521 tank, so apart from the printing, they are identical. As for the lid insert and centre column, they are also interchangeable between the 25xx, 28xx, and 15xx lids.

I'm fortunate to have all three tanks, so can do quick comparisons like this.

 

[Peter Black]

Thanks guys. Looks like time to shoot a couple of sheets of B&W at the weekend and run them through this to check for light leaks and suchlike before I go for E6.

 

[GeorgesGiralt]

Hello !
The 2509 without a core is not light tight in the tank.
The centre core is the same as the 15xx series. I can't check now if the lenght of he one you own is the one you need (because I'm ill and stuck in bed) but check it and you'll be fine.
Jobo parts are all the saame (tis made them successfull by reducing the referenc number in stock)
Hope this helps

 

[Peter Black]

Great timing Georges as I was going to be trying it out tomorrow, so now I'll know to make sure the core is in. Now if anyone has thoughts on the volume of dev for rotary processing in this tank, I'd be pleased to hear them.

 

[grahamp]

A single 2509 reel in the right-size tank should be 270ml for rotary processing. You can go a little over, but too much and it will leak out, and too little risks under developing the sheets nearest the core. Make sure you have enough active ingredient for the number of sheets at your chosen dilution.

 

[Peter Black]

Thanks Graham, I'm looking at 1+50 Rodinal @ 11.5 mins for Acros. Suggested time would be 13.5 and I've knocked off 15% for the Jobo as per the recommendation. Sound OK?

 

[GeorgesGiralt]

hello !
For solution volume you can find on Jobo site the exact value. (if you want to use this tank by hand like a 35 mm tank by inversion, you need around 1.450 litre of sol.)
But the specified Jobo volume is the minimum to wet all the film in the tank. Then you have to think about chemical efficiency :
PMK need 500 CC for one 35 mm film ( 4 sheets of film) so you'll have to use around 750 cc of working dev to process the full 6 sheets.
Kodak state that you need 100 cc of Xtol stock for the same 135 film. So if you use the Kodak figure, you will use around 150 cc Xtol, have enough processing power for the 6 sheets but won't process them because the center sheets won't be wet ....
I can't remember the figure for Rodinal, but check it out if you don't want surprises...
Also, bear in mind that there is continuous agitation, so the air in the tank will mix with the dev, and so, will oxidize the dev faster than it should .... This is important for highly dilute products.
Last but not least, the Jobo motor can't handle heavy loads ( around 600 cc for the CPE and a thousand for CPA/CPP) So if the dev is PMK and you use a CPE2, you overload the machine. (the solution is to process the film with half the volume for half the time and then change solution for the remaining half. This overcome both overload and oxidation)..
Conclusion : Make some tests with film of no significant importance .....
I advise you, for E6 process, to stick to Jobo instructions (and carefully read the instructions in the Kodak E6 single use chemistry kit which are very detailed.

 

[GeorgesGiralt]

Peter, On first try, I won't reduce processing time because of oxidation. But, do not process highly valuable film for this try ;-)

 

[RobertV]

Last but not least, the Jobo motor can't handle heavy loads ( around 600 cc for the CPE and a thousand for CPA/CPP)

For B&W on room temperature you have to install the "light rollers" (Leicht Roller) to have less resistance on the motor torque.

Rodinal in rotary development is killing the acutance of this developer. So you're loosing an interesting parameter of this Para-Amino Phenol developer.

 

[Peter Black]

Thanks guys. This is really only a test to make sure the drum is light-tight, so it's a cheapskate single sheet in a readily available developer, rather than making up a batch from powder.

 

[Peter Black]

A quick update just to confirm it worked out fine and the film is hanging up to dry now. Many thanks for all your help!