meopta meochrom issues - mixing chamber reflective paint?

Discussion in 'Darkroom Equipment' started by octofish, Dec 16, 2011.

  1. octofish

    octofish Member

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    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. LCEL

    LCEL Member

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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. octofish

    octofish Member

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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. Jojje

    Jojje Member

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

    hadeer Subscriber

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  6. hadeer

    hadeer Subscriber

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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. octofish

    octofish Member

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    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. octofish

    octofish Member

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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. ic-racer

    ic-racer Member

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  10. MartinP

    MartinP Member

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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.
     
  11. octofish

    octofish Member

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    It's the first version of the meochrom. The mixing box is definitely different than the ones available for meochrom color-3's etc. It's more spherical, rather than a square looking box. I got a supplier to send me photos to compare and they are different. Not to say they wouldn't fit, but my guess is they wouldn't.

    The reflector most definitely isn't built in. It fits in around the bulb, with a little tongue that slots into a little bracket on the bottom of the head chassis which is then secured with a long thumb screw. I doubt it's been modified. It all looks original to me, and certainly doesn't run off mains voltage. I use an external 12v transformer (which I need to check voltage for still - been moving house and my multimeter is at the bottom of a box somewhere.)

    Interesting about the bulb socket. How does it affect the performance of the bulb do you know? I would have thought it just serves to mechanically hold the bulb in place. Any idea how I would know if it's causing problems (apart from bursting into flames, obviously)?
     
  12. MartinP

    MartinP Member

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    Sounds like your Meochrom is indeed much older than the ones I have used. Sorry for the unfounded optimism!

    The usual thing with any low-voltage, high-current halogen socket is due to the temperature - there can more easily be a little bit of corrosion on the socket or bulb-contact. That puts the resistance up a fair bit so you get a much hotter socket and probably a lower current through the bulb. The halogen bulbs I have used in enlargers are different sizes, but have all had the standard two pin connector on the back. It looks like two little rods and these slide into a ceramic socket with springy contacts inside. The socket itself usually has heavy multi-core cable which is connected to the rest of the device with screw connectors, or some proprietary equivalent.

    Over here we have the second-hand boards with plenty of meopta parts and enlargers. They were very popular in amateur use as they are well made and lined up accurately (in my experience, ymmv as they say). Maybe you can replace the whole enlarger for thirty euros or so? That would make much time or money expenditure, on repairs of the current one, less practical perhaps but it is an option.

    If I see an older pattern of head for sale here I will let you know. They don't weigh much after all, so long as I didn't need to send the transformer!
     
  13. FRANOL

    FRANOL Member

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    Have a same problem with reflector on Meopta Meochrome color head.Can't have a good contrast because yellow metalic paint on reflector and it was like Y filter is always on.I have clean this yellow paint with fine sand paper until glass surface was mat.Glass surface must be mat because I have repaint reflector with aluminum heat resistance (600°C) paint.It's cheap paint here in Croatia (0,2 l about 4$).I have paint reflector twice inside and twice outside and next day put reflector in the oven (200°C) for about 20 min.Now you have nice silver heat absorbing color neutral reflector.Mixing chamber was repaint with white acrylic paint from hobby shop which is heat resistance (160-180°C).Halogen bulb surface is about 250°C.Because I have another color head (for parts) I have change Cyan filter with another Magenta and now there is 2 Magenta and 1 Yellow filter.With two Magenta on this color head it's possible to reach full contrast on any paper.
     
  14. FRANOL

    FRANOL Member

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    There is one more thing about Meopta Meochrome.Because of dust it's better that enlarger is grounded.This color head is not grounded..Trafo is grounded but head not.Cable from color head have plug with 3 contact but cable is with 2 wire.Female connector on the trafo have only 2 "live" contact,the third contact for ground doesn't exist inside female connector.Nearest ground contact that you can make is under big screw on trafo and the other end of the wire under big screw on the top of color head.Just my 0.02$.
     
  15. octofish

    octofish Member

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    Nice one. I'll have to try the paint thing. Im suspect my reflector is still affecting the colour of the light a little despite my bodgy foil fix. Contrast always seems a struggle but I've still not done the work to confirm that it's the enlarger and not development. Will have to try the earthing thing too.

    Thanks for the comment!