Jobo CPE-2 and 3004 drum

[sorin]

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.

[Fotos53]

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.

[david_nash]

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!

[sorin]

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.

[struan_gray]

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.

[john_henderson1]

Hmmm...the wiper motor thing is interesting, but can a Mercedes wiper

motor really be an <em>economical</em> replacement?

 

<p>

 

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

[sal_santamaura]

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.

[sorin]

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.

[kevin_kolosky]

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

[sorin]

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.

 

<p>

 

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

power supply.

[kevin_kolosky]

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

[schatzie_walton]

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.

 

<p>

 

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.