Jobo CPE-2 and 3004 drum : LUSENET : Large format photography : One Thread

I just wanted to let anybody interested that contrary to the manual and the information on the Jobo site, the 3004 drum (allowing developing of 4 sheets/paper up to 8x12") actually fits in the Jobo CPE2. I just got the drum and I was prepared to modify the bath to make it large enough but it doesn't need to be. It fits perfectly (barely of course). And for whiever is concerned about the motor not being strong enough, the JOBO CPE2+ has the same motor that the CPP has (the one that was "designed" for the 3000 series drums). So, basically, what I'm saying is that the proffesional drums are actually working with the CPE2.

-- Sorin Varzaru (, March 29, 2001


Thanks for the information...I have a CPE2 and process 4x5 in the other sheet film tanks and it's not fun trying to load the film in the dark with those plastic clips, that holds the film in position in the tanks during processing. I'm going to look the into 3004 drums ASAP.

-- John Miller (, March 30, 2001.

Great! I've just got a 10x8" back for my camera, and although I'm still waiting for my film, (Kodak Tri-X 10x8" is not imported by Kodak UK so my normal supplier has been waiting weeks for it), I was wondering about the possibilities of using my CPE to process it. I've been using Pyro on my 5x4" negs in a CPE, and would like to be able to use a similar method with the 10x8". I thought I might have to turn to tray processing as I can't afford a CPP at the minute - the Expert drums are expensive enough!

-- David Nash (, March 30, 2001.

A followup. I have to mention that the CPE2 I have (not CPE2+), being the one with the weak motor kinda struggles with the 3004. It rotates it (I had it on for 2 hours) but it looks like it's at its limit. It's true that my CPE2 is very tired anyway and it has sometimes troubles even with the 1520 tank so a unit that functions properly might work even better.

-- Sorin Varzaru (, March 30, 2001.

I am told that Jobo uses a motor originally sourced as a windscreen wiper motor for Mercedes. Somewhere on the web (ha!) is a page with a part number and instructions for fitting a replacement. Only gotcha: check you don't overload the power supply.

-- Struan Gray (, March 30, 2001.

Hmmm...the wiper motor thing is interesting, but can a Mercedes wiper motor really be an economical replacement?

Wonder if I can stick in a GM wiper motor.... :)

-- John H. Henderson (, March 30, 2001.

What rotation speed is provided by your CPE-2? Even if it's the same motor as a CPP, my CPE-2+ rotates at 75rpm vs. much slower for the CPP. If your CPE-2 is also turning this fast, the motor will not likely last long, even if it wasn't tired to start with. Most probably the CPP has some gearing to reduce rotation rate; without it, load on the motor would be proportionately greater.

-- Sal Santamaura (, March 30, 2001.

After I made some research it seems like it's not the motor that has a problem but the power source. Since I am in fact an electric engineer I will probably change the source with a more powerful one.

-- Sorin Varzaru (, March 30, 2001.

Sorin Since you are an electrical engineer I have an interesting question for you. Why is it that when we buy all of these items we have to keep buying the small computers that are in them. or to put it another way, why cannot a motor be somehow hooked up to a computer such that the programs could be put into the computer and away we go. Same for a densitometer. Same for alot of other stuff that requires programming. Why not design things to take advantage of what we all already have so they don't cost so damm much. Kevin

-- Kevin Kolosky (, March 30, 2001.

Kevin, selling a device that requires a 3rd party computer to run would be IMO very difficult to sell. You'd need long wires to connect it (I don't have a computer in the bathroom), you'd run into compatibility and interference problems and the device would need a dedicated control chip anyway. Overall, it would cost the same.

In this particular case it's not even a computer, it's just a DC power supply.

-- Sorin Varzaru (, March 30, 2001.

Sorin Yes, but that power supply is hooked up to something inside that machine that tells it how long to run and tells a water heater how much to heat the water and all sorts of other stuff. In industry and commerce devices are hooked up to computers all of the time. Why doesn't this happen in the photography world? we are having to buy a new "computer" for every device we purchase. Kevin

-- Kevin Kolosky (, March 31, 2001.

The problem with the JOBO CPE2 motor relates to the method JOBO uses to control the speed, not the motor per se. In position "1", approximately 12 volts are present on the motor windings and in position "2" 24 volts. In a motor, torque is proportional to current which is proportional to voltage.

To get more "torque" I have designed a circuit board (and installed one in my CPE2) which borrows from robotics to pulse 24 volts to the motor. If the pulses are on 50% of the time, the motor operates at 50% speed, but with much more torque! An "H-Bridge" is used to reverse the motor every 1 1/2 turns. Any one interested should email me directly.

-- Schatzie Walton (, May 09, 2001.

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