Durst Laborator Electronics Repair?

Discussion in 'Darkroom Developing and Printing' started by Thor Lancelot Simon, Jun 30, 2005.

  1. I have a Durst Laborator 184 8x10 enlarger. I am not sure exactly who
    owned it before I did. It's a somewhat odd unit with a Super Chromega
    instead of the Durst head and, it seems, possibly aftermarket powered
    focusing.

    The powered focusing just failed. I *think* the problem is the motor
    control box that sits behind the head and takes 120V and the input
    from the wired remote, and connects to the small electric motor that
    adjusts the focusing bellows.

    That box is marked "KHB Fotografix" with a defunct phone number and
    address in Mississauga, Ontario. Inside are some rather old electronic
    components I am not entirely sure I can easily replace, including what
    seems to be a strange 6-way relay, a very large electrolytic capacitor,
    and an old Motorola SCR bolted to a giant heatsink (I can probably find
    another source for the SCR, but I'm particularly concerned about the
    strange relay).

    I would consider just buying a modern off the shelf motor controller
    but the motor itself has been painted flat black so I can't figure
    out any of its specifications. And if the motor is what's failed, I
    am not quite sure what to do.

    Does anyone have any good first ideas on how to get this fixed,
    assuming brute-force replacement of all components on the motor
    control board does not prove sufficient? If the motor is a standard
    Durst item, maybe I can get a new control box from someone else. Or
    the specs for the motor, at least. If Durst actually sold motor control
    boxes from "KHB Fotografix", maybe I can get a replacement... sigh.
     
    Thor Lancelot Simon, Jun 30, 2005
    #1
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  2. Thor Lancelot Simon

    Nick Zentena Guest


    KHB is a repair shop. Distributor.

    http://www.khbphotografix.com/

    They sell parts. Do service. Etc.

    Nick
     
    Nick Zentena, Jun 30, 2005
    #2
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  3. Yep. I just talked to Kevin there on the phone. He was amazingly
    helpful.

    My motor control box is probably fine -- it turns out there are
    microswitches at the limits of travel along the focusing rail and
    on the focus lock lever -- I didn't realize the 184 even had a focus
    lock lever. We think that what probably happened was that the cord
    between the controller and remote control failed, and while diagnosing
    this I probably nudged the focus lock lever, thus disabling the motor
    control box entirely.

    Kevin says that he built about 20 L184s with motorized focus and Omega
    colorheads for a customer in the early 1990s and that he periodically
    hears from people who have bought them on the used market in recent
    years. He says this is the first failure of any kind he's ever heard
    about in the motorized focus assembly at all (and, since we think it's
    the cord that actually failed... it's not even clear that this really
    counts. :)).

    These units also have custom 8x10 hinged glass negative carriers. He
    can adapt these to accept smaller carriers from most other enlarger
    systems but the machining setup is quite expensive. If there's anyone
    out there interested in having that done, I'd be willing to go in
    halves on it -- it would probably be a few hundred bucks each.

    I originally wasn't able to find KHB because their area code has
    changed -- their current number is on the web site you mentioned.

    I was very very impressed by their willingness to help on the phone
    and they sounded very competent.
     
    Thor Lancelot Simon, Jun 30, 2005
    #3
  4. KHB was a repair outfit for strobes, enlargers, etc. They probably
    fixed the enlarger at one point[?]
    What you most likely have in the box is a transformer [to make 120VAC
    into 12VAC[as an instance], a rectifier to turn AC into DC and a filter
    capacitor to smooth out the DC. The relay reverses the motor: disconnect
    it and reconnect it the other way round and it may also have some other
    function.

    First: is there a fuse? And if there is, is it OK?

    Second: The problem is in either the box or the motor, right?

    Can you turn the motor shaft by hand/pliers. If you can't
    the problem is in the gear box. If you can a bit, and the
    enlarger moves a bit then there is jam in the focus mechanism
    after the gear box. If you can turn it freely (or some
    approximation of thereof) and the lens board goes up and
    down then the motor may be shot - or may not. Proceed:

    Disconcert the motor - it should unplug. Does the relay go
    click when you play with the focus control?

    NO:

    Chances are the transformer or rectifier are bad. A bad
    capacitor will result in blown fuses or poor motor performance
    (though most wouldn't notice the decrease in motor performance
    in this application). If you have some electronics knowledge,
    or know someone who does - ham radio operator, engineer, tech.
    etc. - you can tell what went bad by probing around with a
    voltmeter. Does anything look or smell overheated, discolored
    or burned?

    A second failure mode is the AC cord going to the box. Often
    the wires break inside the insulation. If you have a trouble
    light or voltmeter check that 120VAC is getting to the box.

    YES:

    The motor may be bad. Try a 6V battery, if
    it doesn't move try a 12V. If you get a big spark when you touch
    the wire to the battery the motor is jammed mechanically or has
    an internal short.

    If the motor moves then there is a problem with the connector
    and/or wire from the box to the motor. Plain old lamp cord can
    be used to replace the wire.

    If electronic parts have blown they can be replaced. The parts may
    not look like the originals but they will work like them.

    If the motor is fried you may have a problem. Scrape some paint off
    to reveal any decals or nameplates. Google on names and part numbers.

    There is an outfit that sells _large_ format refurbed Durst enlargers.
    They may be able to help.

    There are places than repair motors, but usually only big ones. There were
    also places that repair hand-drill motors [though there may not
    be any of these left...].

    How big is the motor in question?

    Plain off-the-shelf motor controllers are meant for factory use with
    _big_ motors, run on 440V 3 phase [or some such] and cost mucho $$.
    There may be exceptions, I don't know of any.

    A good place to try are the places catering to the home-made robot
    crowd. They have motors, small controllers, gearboxes etc.
    There may be a home robotics newsgroup.
     
    Nicholas O. Lindan, Jun 30, 2005
    #4
  5. Definitely the way to go. Ignore my previous post. I too Googled for
    photografix with no joy, try again and there it is.

    "Google twice - post once."
     
    Nicholas O. Lindan, Jun 30, 2005
    #5
  6. Thor Lancelot Simon

    Nick Zentena Guest

    416 code? That must be a pretty old number.

    They are. Offical repair shop for Omega IIRC. Install,service and sell
    Deveres. Mostly aimed at the pro market.


    I bought a rebuilt Durst 4x5 from them. It's 30 years old but other
    then a slight mark on the baseboard it could be brand new.

    Nick
     
    Nick Zentena, Jun 30, 2005
    #6
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