JOBO RPM

[Bruce Osgood]

Does anyone have a Jobo (CPE 2+) that turns at something other than 75RPM?

 

[RGyori]

I believe that when Jobo introduced the CPE2+ they limited it to one rotational speed in response to reports that the slower speed on earlier models yielded inconsistent development. Of course there could be some home-modified units out there but that would not be a modification that Jobo would support.

Personally I have had no problems with Jobo's single speed arrangement using the 2500 series tanks to develop 4 x 5 negatives.

 

[pentaxuser]

Does anyone have a Jobo (CPE 2+) that turns at something other than 75RPM?

I have the earlier JOBO CPE with speeds labelled 1(slow) and 2 (fast). Certainly RA4 needs the fast speed to cover the paper with chemicals fast enough and consistently. Interestingly in his 1992 book"The Rotary Processor Manual" John Tinsley talks about the slow speed F in the older processors giving uneven development and the fast speed P is much better, giving about 70rpm.

So it would seem that 70/75 rpm is fine for everything and that with hindsight JOBO would never have designed a slower speed. Mind you, if you're like me you're always left asking the question"So why did JOBO bother with a slow speed. They must have had something in mind.

Nice if you could get an answer but given that the CPE's design is about 30 yrs old the original designer will long since have retired and evidence for his thinking is probably destroyed under records retention policy.

Pentaxuser

 

[Mick Fagan]

I have the early JOBO CPE2 with speeds labelled 1(slow) and 2 (fast) as well. I have been using it since new in about 1987/88. I have the lift and have developed all of my films the same way since I started.

High speed for the first 15 seconds, then slow speed for the remainder. I change up to high speed for every chemical change. I have done B&W, E6, B&W reversal, 4x5 colour print film, 4x5 duplicating film, Kodak Infrared and some lith film as well.

For Prints, both B&W & colour along with Duratrans I always used the high speed setting.

I worked for a large graphic arts firm at the time I bought the unit and had a good relationship with the Australian distributor for Jobo's, repair facility. The technicians at the time told me that most of the motor problems were down to a few simple things the way they saw it. There wasn't one particular thing that appeared to be a cause of motor failure, although some people who put 8 rolls of 35mm film and 1 litre of developer, did seem to burn motors out.

In short, I think they put one speed on the later models as the market they were aimed at was really amateur and the less decisions to make the less problems they may encounter.

My machine has processed over 3,000 rolls of film and a few thousand 8x10 colour prints and still runs sweetly, although I did have to pull the bellows on the lift apart and re-stick them.

Mick.

 

[pentaxuser]

I have the early JOBO CPE2 with speeds labelled 1(slow) and 2 (fast) as well. I have been using it since new in about 1987/88. I have the lift and have developed all of my films the same way since I started.

High speed for the first 15 seconds, then slow speed for the remainder. I change up to high speed for every chemical change. I have done B&W, E6, B&W reversal, 4x5 colour print film, 4x5 duplicating film, Kodak Infrared and some lith film as well.

For Prints, both B&W & colour along with Duratrans I always used the high speed setting.

I worked for a large graphic arts firm at the time I bought the unit and had a good relationship with the Australian distributor for Jobo's, repair facility. The technicians at the time told me that most of the motor problems were down to a few simple things the way they saw it. There wasn't one particular thing that appeared to be a cause of motor failure, although some people who put 8 rolls of 35mm film and 1 litre of developer, did seem to burn motors out.

In short, I think they put one speed on the later models as the market they were aimed at was really amateur and the less decisions to make the less problems they may encounter.

My machine has processed over 3,000 rolls of film and a few thousand 8x10 colour prints and still runs sweetly, although I did have to pull the bellows on the lift apart and re-stick them.

Mick.

Interesting first hand knowledge there. What is the benefit in quick for first 15 secs then slow for film development. Have you tried a comparison with quick for all the development.

I am always looking for easy ways to improve my negs for printing and remembering to move to slow after 15 secs is easy as long as there is a definite improvement.

Incidentally I once wrote to Ed Buffalo at unblinkingeye about a problem I had had with Rodinal and Ilford Delta 400 using rotary processing(negs were thin) and got a very quick and helpful reply but he did say that in his opinion rotary processing robbed Rodinal of its accutance. Similar advice was given in the book I mentioned. In fact John Tinsley said that this type of developer was unsuitable for rotary processing. However this type of developer apart, Tinsley rates B&W film rotary processing highly. His statement that accutance developers like Rodinal should not be used may be going too far in that rodinal does work in rotary processors. For instance my negs were useable but probably just needed longer development. However Ed Buffalo would contend that they would lose their sharpness. I can't comment as this has been the only B&W film I have ever developed in Rodinal so have nothing to compare the negs with. In other words one of the main benefits for rodinal is negated by rotary processing.

Pentaxuser

 

[Mick Fagan]

I originally thought about rotational speed when I first got the Jobo. The reasoning was that with a fast rotation, the film or paper, was treated to chemicals as fast and as evenly as possible.

With that reasoning, I started the first 15 seconds development at high speed, on my initial rolls of film through the processor. Fifteen seconds was chosen, as by then, I was finished putting containers back into the bath and screwing the lids on, no other reason.

I chose the lower speed for the bulk of the developing purely on the basis that at high speed, the almost instant stopping and reversing the rotational direction, seemed to put quite strain on the unit.

I did exactly the same with paper in the early days. I have had a Durst Printo for many years now and use that for all colour printing and once I reconfigured it to do a large batch of B&W prints. Eight hundred 8 x 10" prints to be exact and it was done in a weekend, what a machine.

Mick.

 

[pentaxuser]

I originally thought about rotational speed when I first got the Jobo. The reasoning was that with a fast rotation, the film or paper, was treated to chemicals as fast and as evenly as possible.

With that reasoning, I started the first 15 seconds development at high speed, on my initial rolls of film through the processor. Fifteen seconds was chosen, as by then, I was finished putting containers back into the bath and screwing the lids on, no other reason.

I chose the lower speed for the bulk of the developing purely on the basis that at high speed, the almost instant stopping and reversing the rotational direction, seemed to put quite strain on the unit.

I did exactly the same with paper in the early days. I have had a Durst Printo for many years now and use that for all colour printing and once I reconfigured it to do a large batch of B&W prints. Eight hundred 8 x 10" prints to be exact and it was done in a weekend, what a machine.

Mick.

OK. Thanks. Has anybody done a comparison between this method and constant high speed. Does the fast then slow increase the time needed compared to fast only or is it the case that slow constant rotation affects development just as much as fast. In other words is there speed beyond which development is unaffected by any increase.

Printing obviously takes up much more of any JOBO's time than film developing so while slow speed must put less strain on the unit its beneficial effect on the motor would be marginal. However if printing could be done at low speed as well then there would be real benefits for the life of the motor? Or so one would think.

Anyone tried low speed printing?

Pentaxuser