Jobo auto lab 1000 over heating

[skebbell]

Hi there,

I’ve recently purchased a jobo autolab 1000 second hand to develop my large format c41 and e6 film. I’ve ran it up today using the e6 normal setting, using water not chemicals. The bath filled up fine and heated fine, the machine then started and i recorded 39 degree water bath. I then measured the temp coming out of the discharge of tank 1 and it was perfect at 38 degrees. I then measured the second and it came out at 41 degrees. The third tank came out at 45 degrees. I then checked the water bath and its temp was running at 48-50 degrees, way above what is mentioned in the manual.

I was wondering if anyone has had this issue before and might be able to offer some insight? I imagine it is the cutoff isn’t working when the bath reaches 41 degrees but am unsure how to fix this.

Thanks, Sean.

 

[koraks]

Have you gone through this thread to pick up hints? https://www.photrio.com/forum/threads/jobo-atl-2-rebuilding-project.172119/

If I were to hazard a guess, there's a problem with the water jacket temperature sensor on your machine. It might have become disconnected, or the sensor itself might have failed. I'm not sure what kind they used on these machines, but probably a fairly simple NTC. I'd start by locating the sensor and measuring its response to different temperatures to see if it works OK, and also poke around with a continuity tester to see if the signal from the sensor is routed correctly through the machine to whatever ADC that's supposed to pick it up.

It would evidently help if you had a service manual for the ATL1000; you might have to google around a lot to find clues. Perhaps the other ATL's are conceptually similar and service manuals of those might be of help, but there are bound to be all kinds of subtle (or fundamental) differences.

If you're lucky, it could be a simple fix. But be prepared for many hours of troubleshooting your machine.

 

[Lachlan Young]

The ATL 1000 and 1500 use a sensor that starts the process when the temperature goes over the threshold defined by the program - i.e. put too warm chemistry in & it'll immediately start rather than pumping cold water for cooling. I'd need to check, but I recall they use a degree of fly-through - even so, it shouldn't be going that hot. It sounds like the water heater's control isn't switching properly when it reaches temp, but the process start is still kicking in as the threshold point is being passed. I recall an opposite issue where the threshold sensor had gone wrong and would start the process before it reached 38c. I'd suggest contacting Jobo & seeing what they recommend.

 

[koraks]

but the process start is still kicking in as the threshold point is being passed.

Yeah, that's a relevant point. Given this, I'd also check the relay that controls the heating element. I would expect they connected it to the relay's NO contact, but in case they for some reason used the NC contact, a stuck relay or a failure of its control signal might also be the issue.

 

[Sirius Glass]

Contact the Darkroom Doctor by email for support and help. Go see what is posted on www.darkroomdoctor.com Dave & Norma C. Smith are the owners and operators of Electromechanical Services, and on the board of FreeStyle which is a Photrio supporter. Email: joboman@aol.com