JOBO ATL2 cold water problem

honzaM · Nov 11, 2023

Hi everyone,
I would like to ask for an advice. Our JOBO ATL2 has recently started to develop an issue that for some reason the cold water solenoid sometimes does not close when running at 20°C. Therefore resulting in very low temperature and possible water overflow if not monitored constantly. The issue does not seem to appear when running at 38°C I have recently swapped the lift motor cause it stopped working but otherwise the machine has been running without any issues for the past 10 years or so.

We used to have a second unit with the exactly same problem with the only difference that the cold water solenoid never closed so we did not really use that one.

Should I look for the problem in the solenoid itself, or is it something related to its control circuit (if so, could anyone advise?), or could the problem be temperature management related?

mshchem · Nov 11, 2023

I would suspect that the solenoid valve has dirt or foreign matter fouling the plunger preventing it from closing properly.

mshchem · Nov 11, 2023

Most solenoid valves can be split open by removing screws, I've worked on these valves on laboratory equipment, many cn be cleaned up, rebuilt

honzaM · Nov 11, 2023

mshchem said:
I would suspect that the solenoid valve has dirt or foreign matter fouling the plunger preventing it from closing properly.

Hi,
Thank you for your quick response. I will definitely look into that. But the setup we have has multiple solid particles and ionts filters in place. So I wasn't thinking it would be likely.

koraks · Nov 11, 2023

honzaM said:
But the setup we have has multiple solid particles and ionts filters in place.

Filters aren't perfect. And scale can build up even if your filters are perfectly maintained and effective.

Follow @mshchem's advice and inspect/revise the solenoid. The fact that it still (sort of works) at a higher temperature suggests mechanical friction might be part of the problem, which may alleviate a bit as things warm up a little.

And welcome to Photrio!

Tim Stapp · Nov 11, 2023

I've tagged @Fred of Wisconsin to this. He's rebuilt/repaired a number of these, right down to circuit board components.

Kino · Nov 11, 2023

If you need to lubricate solenoids or valves, investigate Anhydrous Lanolin. We use that on sticky ball valves in film processors; it sticks and stays on but doesn't migrate or contaminate the fluid being controlled.

It is expensive, but a little goes a very long way...

mshchem · Nov 11, 2023

Another thing I've seen is that the membrane seal or the seat can become damaged in the valve. Rarely the coil would go bad (electrical fault) where the coil fails to pull up the plunger.

honzaM · Nov 12, 2023

Tim Stapp said:
I've tagged @Fred of Wisconsin to this. He's rebuilt/repaired a number of these, right down to circuit board components.

Thank you.

honzaM · Nov 12, 2023

Kino said:
If you need to lubricate solenoids or valves, investigate Anhydrous Lanolin. We use that on sticky ball valves in film processors; it sticks and stays on but doesn't migrate or contaminate the fluid being controlled.

It is expensive, but a little goes a very long way...

Thanks I will see if it can be opened at all. As there are no screwes I'm a little bit afraid that the options will be quite limited.

honzaM · Nov 12, 2023

mshchem said:
Another thing I've seen is that the membrane seal or the seat can become damaged in the valve. Rarely the coil would go bad (electrical fault) where the coil fails to pull up the plunger.

Thanks, I will do some checks and tests and will get back here after the initial cleanup.

honzaM · Nov 12, 2023

Thank

koraks said:
Filters aren't perfect. And scale can build up even if your filters are perfectly maintained and effective.

Follow @mshchem's advice and inspect/revise the solenoid. The fact that it still (sort of works) at a higher temperature suggests mechanical friction might be part of the problem, which may alleviate a bit as things warm up a little.

And welcome to Photrio!

Thank you

honzaM · Nov 12, 2023

mshchem said:
Another thing I've seen is that the membrane seal or the seat can become damaged in the valve. Rarely the coil would go bad (electrical fault) where the coil fails to pull up the plunger.

If it eventually comes to that, is it possible to replace the solenoid with another off-the-shelf available model. Given that the new one runs at 24V and has the same inlet / outlet is there anything else I need to pay attention to?

Dustin McAmera · Nov 12, 2023

When I used occasionally to buy solenoid valves (not for photographic machines) they came with one of three grades of seal; butyl rubber for common liquids, nitrile with a bit more chemical resistance, and viton for aggressive chemicals. I imagine yours is ordinary butyl rubber, but it would be best to check.
IIRC valves could also be normally open (you apply voltage to shut it) or normally closed.

Kino · Nov 12, 2023

honzaM said:
If it eventually comes to that, is it possible to replace the solenoid with another off-the-shelf available model. Given that the new one runs at 24V and has the same inlet / outlet is there anything else I need to pay attention to?

Best if body is plastic or stainless steel; avoid iron for obvious reasons. Might check "food grade" machine part suppliers; Otherwise... none that I can think of right now.

ic-racer · Nov 12, 2023

I recently replaced the water valve solenoid on my home's humidification system. These solenoid valves do go bad. Finding a replacement for your Jobo should not be too difficult. Probably looks something like this.

JOBO ATL2 cold water problem

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