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  1. #1

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    Temperature Probe for Zone VI Compensating Developing Timer

    I have a couple Zone VI Compensating Developing Timers, one now that is in need of a replacement temperature probe. Since I like this tool, I'd like to get a couple of probes in order to have one on hand for the future. I have a quote from Calumet, who will make them for me (no original parts left in stock apparently) for $75 each.

    While this is a reasonable offer, I'm hoping for a cheaper solution. I have no idea of the probe specs., voltage, etc. and was hoping someone here might be able to either provide me with enough info for me to cobble together my own probe or possibly point me to another source.

    Thanks in advance.

    Doremus

    www.DoremusScudder.com
    Last edited by Doremus Scudder; 06-09-2012 at 05:31 AM. Click to view previous post history.

  2. #2

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    Dear Doremus,

    Post a photo of the probe. the color of the wires could be a clue if it uses thermocouples. If it does, simply get some thermocouple wire of the same type, crimp the wires at one end and you have a probe.

    Neal Wydra

  3. #3

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    Neal,

    Unfortunately, I'm not near my darkroom for a month or so, so I can't post a picture. Google images is no help either.

    The Zone VI compensating developing timer came with two kinds of probes, one is a big, c-clamp kind of thing (see attached photo). The ones I have, however, are simply an 8-inch long metal probe, about 3/16-inch in diameter (oblong really). It attaches to the unit with standard phone wire and an RJ type plug, so, without disassembling, I can't see any wires/colors, etc.

    Best,

    Doremus
    Attached Thumbnails Attached Thumbnails timercompa.jpg  

  4. #4

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    Dear Doremus,

    Guessing wildly, based on the connector it seems that the probe is more likely a thermistor than a thermocouple (with luck, someone else will jump in with better information). If that is the case, I don't see how you could determine the correct thermistor/resistor set to buy as a replacement without a working probe. If it is a thermocouple after all, you might be able to work up a cheap replacement.

    In any case, a visit to the Wikipedia pages on both thermocouples and thermistors as well as to omega.com should help you decide how far you want to take this.

    Good luck,

    Neal Wydra

  5. #5
    Nicholas Lindan's Avatar
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    The chances are 99.9999%+ that what has failed is either the wire connecting the sensor clamp to the timer or one of the connectors.

    It looks like a telephone cable, if you can unplug both ends just replace it with a known good cable and see if that fixes it. Examine the ends of the cable where it goes into the connector/probe - if it is lumpy then there is a good chance the copper wire inside the cable has broken.

    Telephone connectors become noisy with time. A little spritz of contact cleaner on the connectors may also do the trick.

    The last thing you should be expecting to replace is the sensor element itself. I'd take a WAG and say it is an RTD (thermistor) or a solid-state temperature sensor.

    http://www.omega.com/temperature/z/R...eElements.html
    http://www.ladyada.net/learn/sensors/tmp36.html
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  6. #6

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    Thanks Nicholas,

    I'll try cleaning connections/rewiring before I spring for a new probe and see if that helps.

    Best,

    Doremus



 

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