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  1. #1

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    meopta meochrom issues - mixing chamber reflective paint?

    Hi APUG folks,

    I'm having some issues with the Meochrom color head mounted on my Meopta Opemus 5 enlarger and am wondering if anyone can help.

    The light has been really weak and distinctly yellow since I got it causing problems with needing long exposures and also probably blowing out contrast control. I replaced the bulb which helped a bit but still not great. 8x10 35mm prints need nearly two minutes at f/4.5. I've taken it apart and the light path is generally pretty good, except for two items.

    Numero uno - the mixing chamber is distinctly degraded with the white reflective coating yellowed, cracked and faded. I don't think I'll be able to find a new replacement so its down to fixing it. Can anyone think of a way to recoat the inside that will work well? I saw mention of zinc oxide paint somewhere on the web but not sure what sort or what to use. Any clues? I don't want to shove any old paint in there and have it cook off and create worse problems.

    Numero due - The reflector behind the globe also looks a bit weird. It's a little yellow, and distinctly transparent. Not sure how much this is colouring the light - I don't think it's a lot, but it's definitely transparent so I'm assuming I'm losing light there too. Is this normal? If not, anyone have any ideas for resolving it? Was thinking of just lining it with aluminium foil, but maybe someone has a better idea.

    Thanks for any help...

    -8fish

  2. #2

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    Look for the manual on the WWW.
    Open the drawer just below the Meochrome Color head and take out the diffuser glass.
    Check again on the contrast.
    Also check the voltage output of the transformer.
    Check if the bulb you changed has the same spec's as the original bulb.
    The Meopta 5 with the Meochrome color head should give you very good results.
    Also check your enlargement lenses.

    Best regards,
    LCEL.

  3. #3

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    I've taken out the diffuser from the drawer yeah. The bulb is fine and is brand new, and the one recommended in the manual. I haven't checked the voltage yet cause don't have a multimeter here (I'll do this though) but the naked bulb seems really bright. There's a heap of light there. The mixing chamber is definitely an issue cause it looks terrible inside, and when you look at the light bouncing off it, it's distinctly yellow. I found a thread somewhere (I can't find it now unfortunately) where people were talking about the same issue with the mixing chamber degrading so it's a common issue by the looks of it. I really want to try fix it up a bit. I just don't really know what type of paint will be suitable.

    I have two lenses a schneider 75mm and a moepta anaret-s 50mm and it's really slow with both. The meopta has a little bit of fungus but not bad, and the schneider is clean as a whistle.

  4. #4

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    Automotive type heat resistant paint meant for painting engines and so should be available at least in silver.

  5. #5
    hadeer's Avatar
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    Your times are definitely too long. The mixing chambers were still sold new not so long ago bu Fotoimpex in Berlin. Is this what you mean? http://www.fotoimpex.de/cgi-bin/shop...otolabor&range ub2=Vergr%F6%DFerer%2DZubeh%F6r&vendor=Meopta&pn=1 2&sort=0&items=

  6. #6
    hadeer's Avatar
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    I bought one for the Meograde a few years back. Not expensive and I am sure they will be happy to send one abroad. Success, Hans.

  7. #7

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    Quote Originally Posted by hadeer View Post
    Your times are definitely too long. The mixing chambers were still sold new not so long ago bu Fotoimpex in Berlin. Is this what you mean? http://www.fotoimpex.de/cgi-bin/shop...otolabor&range ub2=Vergr%F6%DFerer%2DZubeh%F6r&vendor=Meopta&pn=1 2&sort=0&items=
    Argh so close! I hadn't seen that and got excited for a sec, but unfortunately it's for the meograde not the meochrom which i have. It's similar but is a different shape, so I don't think it will work. They don't seem to carry the ones I need. Thanks for the link though.

    I bought some artists acrylic in titanium white which the lady in the shop thought might be ok for the application, but I'm not so sure about the heat resistance and colour of reflected light. I'm going to do some tests first. It probably can't be much worse than it is currently though...

  8. #8

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    So for the record - I have managed to get exposures down to well under a minute at 8x10 without needing to open past f/5.6. What I did is I painted the inside of the mixing chamber with several coats of good quality artists acrylic in titanium white (better than zinc, as it's less transparent). I also lined the back of the bulb reflector with aluminium foil making it as tight and smooth as possible.

    I'm not sure how the paint will hold up over time but is going fine so far and I have been printing a fair bit. The foil thing is not an ideal solution, as it's not fully reflective, but you can see clearly that it is reflecting at least some of the magenta light that was being transmitted through the reflector back through into the light path. One problem now is there seems to be a lot more reflected light inside the head itself than previously, bouncing out through the louvres and into my darkroom. Probably cause of the uneven parts of the foil creating irregular reflections. It's not causing huge problems with my setup I don't think, but a better solution would be to try get some reflective metallic paint and use that on the back of the reflector + maybe some black paint in key spots.

    All up - the light seems a lot less yellow, and is definitely much brighter. I can't compare contrast grades with a standard to make sure it's printing at 2 unfiltered, but it seems reasonable and is a lot faster than before.

    -8fish

  9. #9
    ic-racer's Avatar
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    Too bad about the poor reflector. Some Durst enlargers also use bulbs with a separate reflector. Some options I have considered are:

    1) re-coat the existing reflector (link to reflector re-coating service http://www.optiforms.com/refurb.htm)
    2) finding a new reflector in a similar size (link points to Edmond generic cold (dichroic) reflectors http://www.edmundoptics.com/products...productid=1412 and another site http://www.hb-optical.com/English/re...s/elliprfl.htm)

  10. #10

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    I have a couple of Meoptas. One is an Opemus 6 with a Meochrom Color-3, the head one model newer than yours I think. Which Meochrom version-number do you have on your Op-5?

    It looks as though the same mixing box is used for Meograde and Meochrom and Heiland - the difference comes in the filtration rather than the mixing - and there are different designs for 35mm and 6x6 negatives. These boxes are expanded polystyrene with no coating or colour, with a diffuser lens and mounting flange from hard plastic. That material is even used in Leitz Focomat V35s so should be ok from an operational point of view. It may be that someone has previously attempted to modify your enlarger for some reason. The new boxes are 15 Euros, say $20, but you can send a small picture to FotoImpex to confirm the right part. They are pretty helpful.

    So far as I ever noticed, both Meochroms I have used (the current one and an older version on an old Magnifax) have 12v halogen bulbs with inbuilt reflectors, running off a transformer unit. Your description of a separate reflector sounds very odd - is this perhaps a head which is much, much older than the enlarger, or even one which someone has hacked to run on mains-voltage in the past?

    An item which does need replacing every now and then, and which can cause current and colour-temperature problems (and indeed fire!), is the connector for the halogen-bulb but these are a standard part available from any electricians shop.

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