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  1. #1

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    Replacing enlarger power supply

    Hello,

    I recently got a free Vivitar VI enlarger, but the power supply is broke. (Turned it on, got some sparks, then smoke, then nothing...) and I'm trying to replace it. The output is rated at 18.44VAC and 4.5A (ust over 80W).

    One idea I had was a laptop power supply. I see a lot of "universal" power supplies that are in the right wattage. My question is that these universal power supplies often give a range of voltage (e.g. 12-20V). Will this work if I just cut the wires and splice them in? Do I need to do something special to get it to the right voltage? Any idea how these things work?

    Other suggestions? I'd rather not find another vivitar transformer, only to have it also break in the near future.

    Thanks!
    Tim

  2. #2

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    My understanding is the Vivitar power supply is there to provide a STABLE output as well as stepping down A/C to a lower voltage.

    The only thing it's powering is a lamp which doesn't care AC or DC. If I cannot repair the power supply, I would go with any power supply capable of supplying the voltage (AC or DC) and able to supply sufficient current. I would first open it up and see what blew though. I *think* there is a large capacitor in there that can go.

    If you'd like, I can open mine up and see....
    Develop, stop, fix.... wait.... where's my film?

  3. #3

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    When the large electrolytic capacitor overheated in the Vivitar VI dichroic enlarger owned by a friend, the electrolyte leaked out and the power supply was dead. We bought a replacement motor-run capacitor of the same ratings, installed it and it worked perfectly thereafter. The capacitor cost about $8 at Grainger Industrial Supplies about 1997 when we replaced it. So far as I know it continues to work normally since the capacitor was replaced.

    The Vivitar VI dichroic head uses an 80-watt 19-volt EKG lamp. A significantly higher voltage will destroy the bulb.

  4. #4

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    Yup... as far as I know, it works perfectly too.
    Develop, stop, fix.... wait.... where's my film?

  5. #5

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    Ian has the right idea: first see if you can repair the old supply. Determine where the smoke and sparks came from, and see if you can replace the parts involved. If not, you may have to build a new supply. You generally can't just series the outputs from computer supplies, since most of the outputs will share a common ground (even if there are separate leads). These supplies are rather peculiar to the equipment, so replacement can be tricky. They usually provide some kind of voltage regulation, but not always. They usually have peculiar wiring and switching schemes that you have to figure out properly to make the supply work. Building can be an expensive and complicated option. Try repair.

    Another possibility would be to replace the bulb in the Vivatar with a different kind that used 12 or 24 volts (with 80W power). You can find regulated supplies for these voltages easily. That assumes that the enlarger is wired in some simple manner and that you do not have to power a fan. If there is a fan, you may need to replace that, too.

  6. #6

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    Looks pretty nasty inside. I'm guessing the orange/yellow coating all over the inside (some sort of fluid leaked out all over the place?).


    Click image for larger version. 

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    Is the big thing in the middle the capacitor in question, or is that the transformer?

    I found a laptop power supply listed at best buy that is 19V, 100W for something like $30. Might be an easier way to go, I'm thinking? If the output is controlled enough to not fry a computer, I imagine it would be ok for enlarging too?

    Tim
    Attached Thumbnails Attached Thumbnails photo (4).JPG  

  7. #7

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    I just opened mine up. That's much cleaner than mine. An only repairable part is the capacitor which is located at the top of your image behind a shiny metal. To get to it, you'll have to remove the switch, and 3 bolts around it including the ground and it will come out.

    Do you see any charred connection/wire?

    Modern laptop power supplies are switching type. Regulated and isolated. I'd think you should do fine with that but without seeing (and measuring ) it, I can't tell for absolutely sure. If you give me a couple of days, I can see my junk box and have anything hanging around here. Hate for you to spend $30 for something like that.

    Are you in US so I can ship it to you IF I find it?
    Develop, stop, fix.... wait.... where's my film?

  8. #8

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    Quote Originally Posted by treddy View Post
    Looks pretty nasty inside. I'm guessing the orange/yellow coating all over the inside (some sort of fluid leaked out all over the place?).


    Click image for larger version. 

Name:	photo (5).jpg 
Views:	62 
Size:	651.5 KB 
ID:	64244

    Is the big thing in the middle the capacitor in question, or is that the transformer?

    I found a laptop power supply listed at best buy that is 19V, 100W for something like $30. Might be an easier way to go, I'm thinking? If the output is controlled enough to not fry a computer, I imagine it would be ok for enlarging too?

    Tim
    Laptop power supply is not a very good choice because it does not regulate voltage well. It is so because it's a charger and not a power supply. The battery acts as a voltage regulator.

  9. #9

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    By the way, capacitor stores energy. DO NOT handle the connection if your supply was powered in the last few minutes. We are dealing with a failed equipment. Anything is possible. (since you don't seem to be families with electronic circuits)

    Plus, the particular capacitor that's in the original power supply is an old PCB type. Do not touch if you see liquid leaking out.
    Develop, stop, fix.... wait.... where's my film?

  10. #10
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    I have a V1 as well, and its a very good enlarger (or I think so anyway). I have thought about what I would do if the power supply packed up, and I think if I couldn't fix the original PSU, I'd look at replacing the original bulb for a 12V one of similar shape. The original is classed as a "dichroic projector bulb", and there are lots of other dichroic projector bulbs of similar size. The "dichroic" bit means the heat can escape through the reflector of the bulb. When these units were made, halogen lighting was not so popular, now its easy to get 12V power supplies designed for lighting (I agree, a laptop PSU is not the way to go - I doubt it will work well).

    here's a typical 12V PSU for lighting

    http://www.lightbulbs2u.com/105va-di...mer-p-638.html

    You probably won't find an 80W bulb to match the original, so perhaps go up a bit to 100W or down a bit to 50W. You might have to change the bulb holder, but you can easily get these.

    Here's a 100W 12V bulb that would work with the power supply above

    http://www.lightbulbs2u.com/a1231-ef...FUnMtAodU2AAUw

    OK, these are UK, but you must have similar on your side of the pond.

    Just to add, I usually print 8x10, and my print times are in the range 10-20 seconds with the standard 80W bulb. I think I would be tempted to go down to 50W to begin with. All that will happen is print times will be marginally extended. I suspect not by as much as the difference in rating suggests.
    Last edited by mr rusty; 02-16-2013 at 12:32 PM. Click to view previous post history.

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