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  1. #1

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    Thermaphot ACP 505 heat exchangers

    When making colour prints for the first time for a few months (using fresh and unopened chemistry), I noticed the prints were appearing pale and balanced towards green-blue. Increasing development time to 120 seconds increased density as expected with a slight warm shift but demonstrated the developer and bleach fix were / are working correctly. However, on measuring the temperature of both the developer and bleach fix baths, approx. 20ºC was found in several instances over two darkroom sessions. The pumps for both baths were checked with plain water in-situ and are working.

    The Thermaphot manual refers to 'heat exchangers' apparently used to 'save chemisty' however, I'm not entirely clear what the role of these are in this unit; i.e. whether they perform a heating function in this instance. The manual doesn't explain the logic or concept of the machine's operation.

    As the Thermaphot ACP 505 operates a valve control for the three print washing baths which is apparently closed when no print is going through; it would seem difficult for the "chemical" baths to maintain a constant 35ºC.





    The first image shows the two metal bars, connected to these are solution lines running from one side of each dev & bleach fix tank, through the metal tubes to separate pumps for each line and then back into the other side of the tanks. The off-white goo on the floor of the unit doesn't look as though it should be there and so may be related to the issue; however the could also be an issue with the control circuitry. Tempered wash water is provided by an external Intellifaucet.

    I have been using the unit for processing B&W RC prints since the new year; prior adjustment of the controls could mean the baths have never (or not for a while) been at 35ºC / 38ºC. When I first started using the machine in autumn 2008 an amber LED would be lit until the temperature had apparently reached that indicated on the dial (e.g. 35ºC), however this LED stopped operating at some point earlier this year; I forgot to make a note of the date.



    Tom.
    Last edited by Tom Kershaw; 03-27-2009 at 05:50 AM. Click to view previous post history.

  2. #2

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    Can't tell too much from your photo, except those disc shaped units under the clamp look like fixed thermostats. In the second photo, the wires leading into the end under the tubing could be power leads for a heater controlled by the thermostat. Is the white wire from the end of the tube the same braid covered wire going to the thermostat? The corroded looking stuff appears to be a leak from under a thermostat, which may mean the tubing is corroded thru, and took out the thermostat as well. Time to break out the tool kit.

  3. #3

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    Quote Originally Posted by Bob-D659 View Post
    Can't tell too much from your photo, except those disc shaped units under the clamp look like fixed thermostats. In the second photo, the wires leading into the end under the tubing could be power leads for a heater controlled by the thermostat. Is the white wire from the end of the tube the same braid covered wire going to the thermostat? The corroded looking stuff appears to be a leak from under a thermostat, which may mean the tubing is corroded thru, and took out the thermostat as well. Time to break out the tool kit.
    Bob,

    I just had another look. Supported by the clamped rectangular bars, each line contains a circular tube connected to the solution line with another tubular component below; connected to the braid wires, running from the connector block to the tubular component and from the tube to the disc. The discs have some sort of white deposit on them that scrapes off. You may be able to see a slight browning of the braid covered wire on the disc end.

    Tom.

  4. #4

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    Do you have a digital volt meter? If so unplug one wire from the disc units under the clamp and check for continuity, should be approx 0 ohms. Also check for continuity on the two wires going into the heater, which should be the lower tubular component. UNPLUG the unit first!!!!!!!!!! That at least will tell you if the heater or thermostat is gone. You will have dismantle the heater assembly to determine where the leak is. The slight browning of that high temp braid covered wire indicates a poor connection. It could be the crimp on connector, or it just might be due to burnt contacts in the thermostat itself. I'd guess the burnt contacts myself, due to the deposits on the outside, those units are not usually waterproof.

  5. #5

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    The heat exchangers are heated metal tubes that the solutions are pumped thru in the recirculation system of the processor. I believe you have photographed them in your first photo. They have heating elements imbedded between an outer and inner tube. They are not repairable. You should be able to determine if they are OK or failed by disconnecting each one and doing a continuity check on it. They will have some resistance if OK, and completely open circuit if bad. The only thing I have had fail was a pump. I was able to get a replacement, but it has been so long that I don't remember the parts vendor. These units used to be sold by Calumet, and when they were discontinued, I still called Calumet for a reference to a vendor for replacement parts. They were able to provide one at that time. AFAIK, at least on my processor, the wash tanks are not heated at all, just the developer and blix tanks.

    Earlier Nutek made processors, sold under the Durst label had heating elements in the bottom of the developer and blix tanks and were not part of the recirculation system.

  6. #6

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    You can get replacement parts directly from Thermaphot: rkuemmerl@thermaphot.com Phone: 0049 911 277990

  7. #7

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    Schlger,

    Thanks for that information. I have some more photos to post here showing the various components under discussion.

    Tom.

  8. #8

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    Here are the photos:



    The insulation has been pulled back to enable access to the connecting wires; resistance across the heater was measured at 185 Ohms.



    The above components (one on each line) were measured at 0 Ohms.



    As can be seen in the above image, the paste-like substance was or is sandwiched between the 'microtherm' components and the metal support bars for the solution and tube heaters.



    The bare wire seen in the temperature control unit in the above image connects to what looks like sensor in-line with the pumped solution system.






    Tom.

  9. #9

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    The Microtherm components are fixed thermostats, the white paste is standard heat conductive heat sink compound. They would be for overheating protection cutoff.

  10. #10

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    Bob,

    Can you suggest any other tests I should carry out? Would the thermal paste have leaked out due to overheating?

    Tom.

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